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Is chlorophyll living or non living?

Is chlorophyll living or non living?


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Is chlorophyll living or non living, and after boiling the water out of a chlorophyll extract would it still live, as in would it still maintain its properties after re-adding liquid to the dried chlorophyll?

Thank you for any help.


Chlorophyll is organic, not living, which is a fancy way of saying that it contains carbon. As for your question about boiling, it depends on whether or not the heat from boiling will disrupt the chemical bonds and destroy the molecule. According to Wikipedia, chlorophyll a will melt at around 117°C (I'll assume that chlorophyll b is similar), which is higher than the boiling point of water, so if the temperature is strictly maintained, the chemical should stay intact.


Kingdom Classification of Living Organism

In biology, Kingdoms are the highest taxonomic groups of living organisms. Biologists since the time of Aristotle (384-322 BC) have divided the living world into two kingdoms, Plants and animals.

The word “plant” suggests grasses, bushes, shrubs, creepers, climbers, vines and trees and “animal” suggests cats, dogs, lions, tigers, birds, frogs and fish.

Further thought brings to mind such forms as ferns, mosses, mushrooms and pond scrums (algae), quite different but recognizable as “plants” and insects, lobsters, clams, worms and snails that are definitely animals.

But if you have ever had the pleasure of climbing over the rocky shore of the sea coast, looking at the organisms that cling to the rocks or live in a tide pool, you undoubtedly found some things that were difficult to recognize as animals and plants. The one-celled organisms visible under the microscope cannot easily be assigned to the plant or animal kingdom.

The German biologist Earnst Haeckel (1866) in his book Generelle Morphologie der Organismen suggested a three-kingdom system (Protista, Plantae and Animalia). In the third kingdom Protista he grouped all the single-celled organisms that are intermediate in many respects between plants and animals. Herbert Copeland (1956) have suggested establishing a fourth kingdom, originally called Mycota but later referred to as the Monera, to include the prokaryotes like bacteria and blue-green algae, which have many characteristics is common.

They have a single membrane system without a nucleus, and membrane bounded sub-cellular organelles such as mitochondria or chloroplasts. All other organisms are eukaryotes have a more complex structure with a nucleus and other organelles divided by intracellular membranes. R. H. Whittaker (1969) recognized an additional kingdom for the Fungi. The resulting five- kingdom system suggested by him has received wide acceptance. However, this may not be the end of the story. Some scientists have proposed that organisms be divided into even more (may be as many as 8) kingdoms.

Currently most biologists recognize six kingdoms: two prokaryotic kingdoms (Archaebacteria and Bacteria), a large unicellular eukaryotic kingdom (Protista) and three Multicellular eukaryotic kingdoms (Fungi, Plantae and Animalia). Viruses are not included in any of the present 5 kingdoms – mainly due to their many nonliving characteristics (for example, viruses are not cells).

[Note that the equivalences in this table are not perfect. For example, Haeckel placed the red algae (Haeckel’s Florideae modern Floridiophyceae) and blue-green algae (Haeckel’s Archephyta modern Cyanobacteria) in his Plantae, but in modern classifications they are considered protists and bacteria respectively. However, despite this and other failures of equivalence, the table gives a useful simplification]

I. Two Kingdoms Classification:

In his Systema Naturae, first published in 1735, Carolus Linnaeus distinguished two kingdoms of living things: Animalia for animals and Plantae (Vegetabilia) for plants. He classified all living organisms into two kingdoms – on the basis of nutrition and locomotion (mobility).

Linnaeus placed unicellular protozoans and multicellular animals (metazoans) under animal kingdom because of their compact body, holozoic nutrition (ingestion of food) and locomotion. All other organisms were grouped under plant kingdom because of their immobility, spread out appearance and autotrophic mode of nutrition. Thus, the traditional plant kingdom comprised bacteria, algae, plants and fungi

Demerits or Limitations:

(a) The two kingdom system of classification did not indicate any evolutionary relationship between plants and animals.

(b) It grouped together the prokaryotes (bacteria, BGA) with other eukaryotes.

(c) It also grouped unicellular and multi-cellular organisms together.

(d) This system did not distinguish the heterotrophic fungi and the autotrophic green plants.

(e) Dual organisms like Euglena and lichens did not fall into either kingdom.

(f) Slime mould, a type of fungi, can neither be grouped in fungi nor plants. This is because they are wall less and holozoic in vegetative stage, but develop cell wall in the reproductive stage.

(g) It did not mention some acellular organisms like viruses and viroids.

II. Five Kingdoms Classification:

R.H. Whittaker (1969), an American Taxonomist, classified all organisms into five kingdoms: Monera, Protista, Fungi, Plantae and Animal.

He used following criteria for classification:

(i) Complexity of cell structure

(ii) Complexity of body organization

(iv) Life style (ecological role) and

(v) Phylogenetic relationship.

1. Monera (Kingdom of Prokaryotes):

(a) The members of this kingdom are microscopic prokaryotes.

(b) Monerans are mostly unicellular. But some are mycelial, filamentous (e.g. Nostoc) or colonial.

(c) The cells are prokaryotic with one envelope system or organisation.

(d) Cell wall usually present (except Mycoplasma) which composed of peptidoglycan or murein.

(e) True nucleus and other membrane bounded organelles absent.

(f) Genetic material is a circular naked DNA (without histone proteins) lies coiled near the centre of cell called nucleoid.

(g) More than one structural genes (cistrons) arranged together and regulated in units called operons.

(h) Ribosomes 70s type. (30S + 50S type)

(i) Cytoskeleton (microtubules, microfilaments and intermediate filaments) absent.

(j) Flagella if present consists of flagellant proteins.

(k) Nutrition may be autotrophic (photoautotrophic or chemoautotrophic). Saprot-rophic, parasitic or symbiotic.

(l) Reproduction mainly occurs by binary fission. Sexual reproduction (Gamete formation) absent. In some cases genetic recombination occurs.

(m) They are the important decomposers and mineralizes and help in recycling of nutrients in biosphere.

(n) Most are found in deep ocean floor, hot deserts, hot springs and even inside other organisms.

Monera includes archeabacteria, bacteria, cyanobacteria (BGA), and filamentous actinomycetes.

2. Protista (Kingdom of Unicellular eukaryotes):

(a) The members are unicellular and colonial eukaryotes.

(b) Most of them are aquatic and constitute plankton.

(c) Their eukaryotic cell body contains membrane bounded cell organelles like nucleus, mitochondria, endoplasmic reticulum and Golgi complex etc.

(d) They may have cilia or flagella for their movements which show 9 + 2 arrangements of microtubules.

(e) On the basis of nutrition, the protists are grouped as: (a) Photosynthetic protists (protistan algae) like diatoms, dinoflagellates and euglenoids. They are known as phytoplankton’s. (b) Consumer- decomposer protists (slime moulds) and (c) Predator protists (Protozoans).

(f) Both asexual and sexual modes of reproduction are present.

3. Fungi (Kingdom of Multi-cellular decomposers):

(a) The members are achlorophyllus, spore-bearing eukaryotic thallophytes.

(b) It includes unicellular yeasts and multi-cellular mycelial forms but not slime moulds.

(c) Cell wall composed of chitin (fungal cellulose), a nitrogen containing carbohydrate.

(d) Their mode of nutrition is saprobiotic or parasitic. They can also live as symbionts in association with algae as Lichens and with roots of higher plants as mycorrhiza.

(e) They help in decomposition of organic matter and help in recycling of minerals.

(f) Vegetative reproduction takes place by fragmentation, fission and budding.

(g) Asexual reproduction takes place by motile spores (zoospores) or non-motile spores (condia, oidia, aplanospores or chlamydospores).

(h) Sexual reproduction occurs by oospores, ascospores and basidiospores. Sexual reproduction involves three steps: (a) Plasmogamy (fusion of protoplasm between motile or non-motile gametes, (b) karyogamy (fusion of two nuclei) and (c) Meiosis in Zygote producing haploid spores.

Fungi include Phycomycetes (e.g. Mucor,Rhizopus, Albugo etc.), Ascomycetes (e.g. Sacbaromyces, Penicillium, Aspergillus, Claviceps, Neurospora etc.), Basidiomycetes (e.g. Agaricus, Mushrooms Ustilago, Smuts and Puccinia, rust fungi), Deuteromycetes.

4. Plantae (Kingdom of Multicellular Producers):

1. Their members are Multicellular, eukaryotic, chlorophyll-containing organisms. A few are parasitic (e.g. Cuscuta) or partially heterotrophic such as insectivorous plants (e.g. bladderwort, Venus fly trap, Sun few, Pitcher Plant etc.)

2. Their cells are eukaryotic with plastids and cell wall composed of cellulose.

3. Life cycle exhibit alternation between diploid sporophyte and the haploid gametophyte. This Phenomenon is called alternation of generation.

Plantae includes Green algae, brown algae, Red algae, bryophytes, pteridophytes, gymnosperms and angiosperms.

5. Animalia (Kingdom of Multicellular consumers):

1. The members are eukaryotic Multicellular heterotrophic consumers.

2. Cells lack cell walls. They contain glycogen or fat as reserve food.

3. The organization may be cellular level (porifera), tissue level (colenterates), organ level (Platyhelminthes and Nemathelminthcs) and Organ system level (Annelids, Arthropods, Molluscs, Echinoderms and Chordates).

4. Symmetry may be radial, biradial, bilateral or asymmetrical.

5. On the basis of number of germ layers in embryonic gastrula, animals are diploblastic and triploblastic.

6. On the basis of presence of absence of coelom (body cavity) the animals are coelornates, pseudocoelomates or acoelomates.

Merits and Demerits of Five Kingdom:

1. Kingdom animalia become more homogenous with the separation of protozoa.

2. Kingdom plantae also become more homogeneous with the exclusion of bacteria, fungi and some unicellular algal forms.

3. Separation of prokaryotes into a separate kingdom – Monera is due for long time.

4. Separation of fungi from plants is a wise step.

5. Separation of intermediate or transitional forms of unicellular eukaryotes into kingdom – Protista is well thought out. So that the plant and animal kingdoms become more systematic.

6. It brings our phylogenetic relationships in the living world.

1. The Monera and Protista kingdoms are still heterogenous because both include autotrophic and heterotrophic forms and some with or without cell wall.

2. Phyolgeny in lower organisms is not fully reflected.

3. Slime moulds don’t fit in kingdom protista.

4. Red and brown algae are not related to other members of kingdom plantae.

5. Viruses have not been included in this system of classification.

III. Six Kingdoms and Three Domains Classification

In the years around 1980 there was an emphasis on phylogeny and redefining the kingdoms to be monophyletic. The Animalia, Plantae, and Fungi were generally reduced to core groups of closely related forms, and the others thrown into the Protista. Based on rRNA studies Carl Woese divided the prokaryotes into two kingdoms, called Eubacteria and Archaebacteria.

Such six-kingdom systems have become standard in many works. In 1990, Carl Woese proposed that the Eubacteria, Archaebacteria, and Eukarvota represent three primary lines of descent and accordingly he promoted them to domains, naming them Bacteria, Archaea, and Eukarya. This three-domain classification has received notable criticism but has generally displaced the older two-empire system as a way of organizing kingdoms together.

Status of Bacteria:

Initially bacteria were considered as primitive animals by some, primitive plants by the others and a few considered them as primitive fungi. But, now, bacteria are considered as the simplest prokaryotic organisms which evolved about 3.5 billion years ago and treated solely under Kingdom- Monera. On the basis of molecular homology of 16S RNA, monerans are divided into two major groups: the Archaebacteria and the Eubacteria.

Plant-like characters of bacteria:

(2) Some bacterial cells join together to form algae like simple filament.

(3) Bacteria absorb food form the medium in the form of sap (solution) through their general surface.

(4) Some bacteria, like green plants, have the capability of carbon assimilation (photosynthesis) and form organic food.

(5) Bacteria also synthesize some enzymes and vitamins.

Fungi-like characters of bacteria:

(1) Cell wall contains N-acetylglucosamine (NAG).

(3) Nutrition is parasitic or saprophytic.

(4) They reproduce by fission. Hence, related to fission fungi.

Animal-like characters of bacteria:

(2) Absence of true vacuole.

(3) Nutrition heterotrophic.

(4) Reserve food is glycogen.

(5) Motility through flagella.

Biological Status of Viruses:

The status of viruses is uncertain and highly debatable as they exhibit the characteristics of both non-living and living. As viruses are metabolically inert outside the host cells, they cannot be regarded as organism. They can be crystallized, but they cannot be reduced to the status of chemicals, because they have the capability to multiply and infect the living cells. Therefore, Andre Lwoff, a Nobel laureate and the former Director of Pasture Research Institute once said “A virus is a virus” which means they have both Living and non-living nature instead of being either of the two.

Living properties:

1. They have genetic material carrying heritable characters.

2. They can multiply only inside the living host cell.

4. They respond to external stimuli like heat, chemical, UV radiation etc.

5. They are strictly obligate parasites.

Non-living properties:

1. They can be crystallized.

2. They lack protoplasm and cellular organization.

3. Respiration and metabolism absent.

4. Energy storing or utilizing device absent.

5. They cannot be cultured in a non-living culture medium.

6. They lack any evolutionary or phylogenetic relationship.

Because of their acellular nature, viruses are not included under any of the five kingdoms of Whittaker. However, in 1962, Lowff, Home and Tourneir proposed LHT system which was adopted by the International Committee on Taxonomy of viruses (ICTV). LHT system grouped all viruses under a separate phylum ‘Vira’ and divided in form of Linnaean hierarchy.


Comparison of Living and Non-living Things

The various things that make up our world are broadly categorized into two categories, living and non living. In this BiologyWise article, let's compare and contrast the differences between these two categories, in detail.

The various things that make up our world are broadly categorized into two categories, living and non living. In this BiologyWise article, let’s compare and contrast the differences between these two categories, in detail.

In school we all were taught the difference between living and non living things. Whatever could move, talk and display emotions was a living thing and something which was stable, inert, or didn’t talk was a nonliving thing, this was the basic difference I was taught by my parents and teachers when I was a kid. It was so easy to differentiate the things as living and non living with these criteria of differentiation. But even then I had some confusion in mind a flowing river, it has to be living because it moves and also makes noise. Plants, they never say anything nor move, aren’t they non living things?

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So, do we really have adequate knowledge to be able to distinguish these two categories? Because, I have again got some unanswered questions in my mind. The invisible destructive virus, what is it, a living thing or a non living thing? A person in coma due to a severe head injury is referred to as brain ‘dead’, so how can the person be called ‘living’? The comparison between living and non living things is not easy as it seems on a first note. Thus, in my quest to understand the minute differences between these two categories, I have summarized the differences that classify a thing as either living or nonliving.

Point of Comparison Explanation
Respiration Respiration, that is the process of breathing is the key criteria that separates a living being from a non living being. The process of respiration is same in almost all living beings, which generally is taking in oxygen and exhaling carbon dioxide. Humans and most other mammals obtain oxygen through the lungs. Some aquatic animals like fish take in oxygen through their gills. There are some animals that breathe through their skin. But the process of respiration is slightly different in plants instead of taking in oxygen they take in carbon dioxide, and exhale oxygen. The concluding point is that respiration is a key process of survival, be it any living being.
Life Processes Almost all living beings exhibit life processes like metabolism, homeostasis and genetic mutations. There are many complex processes that take place in a living organism’s body. On the other hand, non living things do not undergo these life processes. All the living organisms have the ability to reproduce and give birth to organisms of their kind.
Response to Stimuli Living things show response to stimuli. Humans, plants, fish and animals, all respond to the changes in the surroundings. Non living beings on the other hand would never show response to the stimuli.
Death Living beings follow a life cycle that progresses as birth, growth and death. Death is imperative for any living being non living things would never have to face death. They can be destroyed due to natural calamities or some actions, but they never die.
Composition Cells are the basic constituents of all the living organisms. Plants and animals all are made of countless cells. Cells are essential to perform the basic processes in life. There are number of processes that undergo in living organisms. Non living things on the other hand lack the chemical processes and are composed of matter that doesn’t undergo any chemical change on its own.

As we had discussed earlier, there is confusion to distinguish certain entities as living or non living. I need to mention that there have been varied opinions to classify these entities. Let’s find what science opines about these two categories…

Virus: Living or Nonliving?

Many people consider that viruses are living. The reason people hold this opinion is that there are many viruses that cause diseases and thus cause destruction. But this understanding is wrong. Viruses actually are non living things. They cannot do anything on their own and require the help of the cells in the body of a living organism to multiply and cause the destruction. The destruction causing virus is rendered useless if it has no host.

A Brain Dead Person

Science holds the opinion that a brain dead person (if the entire brain is dead) has actually died because, the inability of the brain to function also hampers the breathing and other bodily functions in the organism, that characterize life. A brain dead person also doesn’t show other common characteristics of life like response to stimuli. Religious groups and certain people find this opinion of science quite difficult to accept, and there is still a debate to characterize a brain dead person as dead or living.

All these concepts, though apparently simple, are difficult to understand. Hopefully, these concepts have helped you understand the complex concepts of living and non living things.

Related Posts

All living things have common traits, irrespective of plants and animals. Scroll down this article to know more about these characteristics of living things.

According to the Carl Linnaeus system of classification, the 5 kingdoms of living things are Monera, Protista, Fungi, Plantae and Animalia. Read on to understand more.

The levels of organization of living things include cells, tissues, organs, organ systems, and organisms. This article gives details of these levels, and other related facts.


Chloroplasts Up Close

Inside chloroplasts are special stacks of pancake-shaped structures called thylakoids (Greek thylakos = sack or pouch). Thylakoids have an outer membrane that surrounds an inner area called the lumen. The light-dependent reactions happen inside the thylakoid.

Our cells have mitochondria (Greek mitos = thread, and khondrion = little granule), our energy-producing structures. We don't have any chloroplasts. Plants have both mitochondria and chloroplasts.

This model of a chloroplast shows the stacked thylakoids. The space inside a thylakoid is called a lumen. Image via Guillermo Estefani (artinaid.com).

Both mitochondria and chloroplasts convert one form of energy into another form that cells can use. How did plants get chloroplasts? Chloroplasts were once free-living bacteria! Chloroplasts entered a symbiotic (Greek syn = together, and bios = life) relationship with another cell, which eventually led to the plant cells we have today.


Contents

A balance of magnesium is vital to the well-being of all organisms. Magnesium is a relatively abundant ion in Earth's crust and mantle and is highly bioavailable in the hydrosphere. This availability, in combination with a useful and very unusual chemistry, may have led to its utilization in evolution as an ion for signaling, enzyme activation, and catalysis. However, the unusual nature of ionic magnesium has also led to a major challenge in the use of the ion in biological systems. Biological membranes are impermeable to magnesium (and other ions), so transport proteins must facilitate the flow of magnesium, both into and out of cells and intracellular compartments.

Chlorophyll in plants converts water to oxygen as O2. Hemoglobin in vertebrate animals transports oxygen as O2 in the blood. Chlorophyll is very similar to hemoglobin, except magnesium is at the center of the chlorophyll molecule and iron is at the center of the hemoglobin molecule, with other variations. [6] This process keeps living cells on earth alive and maintains baseline levels of CO2 and O2 in the atmosphere.

Human health Edit

Inadequate magnesium intake frequently causes muscle spasms, and has been associated with cardiovascular disease, diabetes, high blood pressure, anxiety disorders, migraines, osteoporosis, and cerebral infarction. [7] [8] Acute deficiency (see hypomagnesemia) is rare, and is more common as a drug side-effect (such as chronic alcohol or diuretic use) than from low food intake per se, but it can occur in people fed intravenously for extended periods of time.

The most common symptom of excess oral magnesium intake is diarrhea. Supplements based on amino acid chelates (such as glycinate, lysinate etc.) are much better-tolerated by the digestive system and do not have the side-effects of the older compounds used, while sustained-release dietary supplements prevent the occurrence of diarrhea. [ citation needed ] Since the kidneys of adult humans excrete excess magnesium efficiently, oral magnesium poisoning in adults with normal renal function is very rare. Infants, which have less ability to excrete excess magnesium even when healthy, should not be given magnesium supplements, except under a physician's care.

Pharmaceutical preparations with magnesium are used to treat conditions including magnesium deficiency and hypomagnesemia, as well as eclampsia. [9] Such preparations are usually in the form of magnesium sulfate or chloride when given parenterally. Magnesium is absorbed with reasonable efficiency (30% to 40%) by the body from any soluble magnesium salt, such as the chloride or citrate. Magnesium is similarly absorbed from Epsom salts, although the sulfate in these salts adds to their laxative effect at higher doses. Magnesium absorption from the insoluble oxide and hydroxide salts (milk of magnesia) is erratic and of poorer efficiency, since it depends on the neutralization and solution of the salt by the acid of the stomach, which may not be (and usually is not) complete.

Magnesium orotate may be used as adjuvant therapy in patients on optimal treatment for severe congestive heart failure, increasing survival rate and improving clinical symptoms and patient's quality of life. [10]

Nerve conduction Edit

Magnesium can affect muscle relaxation through direct action on cell membranes. Mg 2+ ions close certain types of calcium channels, which conduct positively charged calcium ions into neurons. With an excess of magnesium, more channels will be blocked and nerve cells activity will decrease. [11] [12]

Hypertension Edit

Intravenous magnesium sulphate is used in treating pre-eclampsia. [13] For other than pregnancy-related hypertension, a meta-analysis of 22 clinical trials with dose ranges of 120 to 973 mg/day and a mean dose of 410 mg, concluded that magnesium supplementation had a small but statistically significant effect, lowering systolic blood pressure by 3–4 mm Hg and diastolic blood pressure by 2–3 mm Hg. The effect was larger when the dose was more than 370 mg/day. [14]

Diabetes and glucose tolerance Edit

Higher dietary intakes of magnesium correspond to lower diabetes incidence. [15] For people with diabetes or at high risk of diabetes, magnesium supplementation lowers fasting glucose. [16]

The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for magnesium in 1997. If there is not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) is used instead. The current EARs for magnesium for women and men ages 31 and up are 265 mg/day and 350 mg/day, respectively. The RDAs are 320 and 420 mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 350 to 400 mg/day depending on age of the woman. RDA for lactation ranges 310 to 360 mg/day for same reason. For children ages 1–13 years the RDA increases with age from 65 to 200 mg/day. As for safety, the IOM also sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of magnesium the UL is set at 350 mg/day. The UL is specific to magnesium consumed as a dietary supplement, the reason being that too much magnesium consumed at one time can cause diarrhea. The UL does not apply to food-sourced magnesium. Collectively the EARs, RDAs and ULs are referred to as Dietary Reference Intakes. [17]

Reference Daily Intake of magnesium [18]
Age Male Female Pregnancy Lactation
Birth to 6 months 30 mg* 30 mg*
7–12 months 75 mg* 75 mg*
1–3 years 80 mg 80 mg
4–8 years 130 mg 130 mg
9–13 years 240 mg 240 mg
14–18 years 410 mg 360 mg 400 mg 360 mg
19–30 years 400 mg 310 mg 350 mg 310 mg
31–50 years 420 mg 320 mg 360 mg 320 mg
51+ years 420 mg 320 mg

The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men ages 18 and older the AIs are set at 300 and 350 mg/day, respectively. AIs for pregnancy and lactation are also 300 mg/day. For children ages 1–17 years the AIs increase with age from 170 to 250 mg/day. These AIs are lower than the U.S. RDAs. [19] The European Food Safety Authority reviewed the same safety question and set its UL at 250 mg/day - lower than the U.S. value. [20] The magnesium UL is unique in that it is lower than some of the RDAs. It applies to intake from a pharmacological agent or dietary supplement only, and does not include intake from food and water.

For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of daily value (%DV). For magnesium labeling purposes 100% of the daily value was 400 mg, but as of May 27, 2016, it was revised to 420 mg to bring it into agreement with the RDA. [21] [22] Compliance with the updated labeling regulations was required by 1 January 2020, for manufacturers with $10 million or more in annual food sales, and by 1 January 2021, for manufacturers with less than $10 million in annual food sales. [23] [24] [25] During the first six months following the 1 January 2020 compliance date, the FDA plans to work cooperatively with manufacturers to meet the new Nutrition Facts label requirements and will not focus on enforcement actions regarding these requirements during that time. [23] A table of the old and new adult Daily Values is provided at Reference Daily Intake.

Green vegetables such as spinach provide magnesium because of the abundance of chlorophyll molecules, which contain the ion. Nuts (especially Brazil nuts, cashews and almonds), seeds (e.g., pumpkin seeds), dark chocolate, roasted soybeans, bran, and some whole grains are also good sources of magnesium. [26]

Although many foods contain magnesium, it is usually found in low levels. As with most nutrients, daily needs for magnesium are unlikely to be met by one serving of any single food. Eating a wide variety of fruits, vegetables, and grains will help ensure adequate intake of magnesium. [ citation needed ]

Because magnesium readily dissolves in water, refined foods, which are often processed or cooked in water and dried, in general, are poor sources of the nutrient. For example, whole-wheat bread has twice as much magnesium as white bread because the magnesium-rich germ and bran are removed when white flour is processed. The table of food sources of magnesium suggests many dietary sources of magnesium. [ citation needed ]

"Hard" water can also provide magnesium, but "soft" water contains less of the ion. Dietary surveys do not assess magnesium intake from water, which may lead to underestimating total magnesium intake and its variability.

Too much magnesium may make it difficult for the body to absorb calcium. [ citation needed ] Not enough magnesium can lead to hypomagnesemia as described above, with irregular heartbeats, high blood pressure (a sign in humans but not some experimental animals such as rodents), insomnia, and muscle spasms (fasciculation). However, as noted, symptoms of low magnesium from pure dietary deficiency are thought to be rarely encountered.

Following are some foods and the amount of magnesium in them: [27]

    seeds, no hulls (1/4 cup) = 303 mg , (1/4 cup) = 162 mg [28] flour (1/2 cup) = 151 mg (1/4 cup) = 125 mg
  • Oat bran, raw (1/2 cup) = 110 mg
  • Cocoa powder (1/4 cup) = 107 mg (3 oz) = 103 mg (1/4 cup) = 99 mg (1/4 cup) = 89 mg
  • Whole wheat flour (1/2 cup) = 83 mg , boiled (1/2 cup) = 79 mg , boiled (1/2 cup) = 75 mg , 70% cocoa (1 oz) = 73 mg , firm (1/2 cup) = 73 mg , boiled (1/2 cup) = 60 mg , cooked (1/2 cup) = 59 mg (2 tablespoons) = 50 mg (1/4 cup) = 46 mg , hulled (1/4 cup) = 41 mg , boiled (1/2 cup) = 39 mg , boiled (1/2 cup) = 37 mg , boiled (1/2 cup) = 36 mg , cooked (1/2 cup) = 32 mg (1 Tbsp) = 32 mg , non fat (1 cup) = 27 mg , espresso (1 oz) = 24 mg (1 slice) = 23 mg

In animals, it has been shown that different cell types maintain different concentrations of magnesium. [29] [30] [31] [32] It seems likely that the same is true for plants. [33] [34] This suggests that different cell types may regulate influx and efflux of magnesium in different ways based on their unique metabolic needs. Interstitial and systemic concentrations of free magnesium must be delicately maintained by the combined processes of buffering (binding of ions to proteins and other molecules) and muffling (the transport of ions to storage or extracellular spaces [35] ).

In plants, and more recently in animals, magnesium has been recognized as an important signaling ion, both activating and mediating many biochemical reactions. The best example of this is perhaps the regulation of carbon fixation in chloroplasts in the Calvin cycle. [36] [37]

Magnesium is very important in cellular function. Deficiency of the nutrient causes disease of the affected organism. In single-cell organisms such as bacteria and yeast, low levels of magnesium manifests in greatly reduced growth rates. In magnesium transport knockout strains of bacteria, healthy rates are maintained only with exposure to very high external concentrations of the ion. [38] [39] In yeast, mitochondrial magnesium deficiency also leads to disease. [40]

Plants deficient in magnesium show stress responses. The first observable signs of both magnesium starvation and overexposure in plants is a decrease in the rate of photosynthesis. This is due to the central position of the Mg 2+ ion in the chlorophyll molecule. The later effects of magnesium deficiency on plants are a significant reduction in growth and reproductive viability. [4] Magnesium can also be toxic to plants, although this is typically seen only in drought conditions. [41] [42]

In animals, magnesium deficiency (hypomagnesemia) is seen when the environmental availability of magnesium is low. In ruminant animals, particularly vulnerable to magnesium availability in pasture grasses, the condition is known as 'grass tetany'. Hypomagnesemia is identified by a loss of balance due to muscle weakness. [43] A number of genetically attributable hypomagnesemia disorders have also been identified in humans. [44] [45] [46] [47]

Overexposure to magnesium may be toxic to individual cells, though these effects have been difficult to show experimentally. [ citation needed ] Hypermagnesemia, an overabundance of magnesium in the blood, is usually caused by loss of kidney function. Healthy animals rapidly excrete excess magnesium in the urine and stool. [48] Urinary magnesium is called magnesuria. Characteristic concentrations of magnesium in model organisms are: in E. coli 30-100mM (bound), 0.01-1mM (free), in budding yeast 50mM, in mammalian cell 10mM (bound), 0.5mM (free) and in blood plasma 1mM. [49]

Mg 2+ is the fourth-most-abundant metal ion in cells (per moles) and the most abundant free divalent cation — as a result, it is deeply and intrinsically woven into cellular metabolism. Indeed, Mg 2+ -dependent enzymes appear in virtually every metabolic pathway: Specific binding of Mg 2+ to biological membranes is frequently observed, Mg 2+ is also used as a signalling molecule, and much of nucleic acid biochemistry requires Mg 2+ , including all reactions that require release of energy from ATP. [50] [51] [37] In nucleotides, the triple-phosphate moiety of the compound is invariably stabilized by association with Mg 2+ in all enzymatic processes.

Chlorophyll Edit

In photosynthetic organisms, Mg 2+ has the additional vital role of being the coordinating ion in the chlorophyll molecule. This role was discovered by Richard Willstätter, who received the Nobel Prize in Chemistry 1915 for the purification and structure of chlorophyll binding with sixth number of carbon

Enzymes Edit

The chemistry of the Mg 2+ ion, as applied to enzymes, uses the full range of this ion's unusual reaction chemistry to fulfill a range of functions. [50] [52] [53] [54] Mg 2+ interacts with substrates, enzymes, and occasionally both (Mg 2+ may form part of the active site). In general, Mg 2+ interacts with substrates through inner sphere coordination, stabilising anions or reactive intermediates, also including binding to ATP and activating the molecule to nucleophilic attack. When interacting with enzymes and other proteins, Mg 2+ may bind using inner or outer sphere coordination, to either alter the conformation of the enzyme or take part in the chemistry of the catalytic reaction. In either case, because Mg 2+ is only rarely fully dehydrated during ligand binding, it may be a water molecule associated with the Mg 2+ that is important rather than the ion itself. The Lewis acidity of Mg 2+ (pKa 11.4) is used to allow both hydrolysis and condensation reactions (most common ones being phosphate ester hydrolysis and phosphoryl transfer) that would otherwise require pH values greatly removed from physiological values.

Essential role in the biological activity of ATP Edit

ATP (adenosine triphosphate), the main source of energy in cells, must be bound to a magnesium ion in order to be biologically active. What is called ATP is often actually Mg-ATP. [5]

Nucleic acids Edit

Nucleic acids have an important range of interactions with Mg 2+ . The binding of Mg 2+ to DNA and RNA stabilises structure this can be observed in the increased melting temperature (Tm) of double-stranded DNA in the presence of Mg 2+ . [50] In addition, ribosomes contain large amounts of Mg 2+ and the stabilisation provided is essential to the complexation of this ribo-protein. [55] A large number of enzymes involved in the biochemistry of nucleic acids bind Mg 2+ for activity, using the ion for both activation and catalysis. Finally, the autocatalysis of many ribozymes (enzymes containing only RNA) is Mg 2+ dependent (e.g. the yeast mitochondrial group II self splicing introns [56] ).

Magnesium ions can be critical in maintaining the positional integrity of closely clustered phosphate groups. These clusters appear in numerous and distinct parts of the cell nucleus and cytoplasm. For instance, hexahydrated Mg 2+ ions bind in the deep major groove and at the outer mouth of A-form nucleic acid duplexes. [57]

Cell membranes and walls Edit

Biological cell membranes and cell walls are polyanionic surfaces. This has important implications for the transport of ions, in particular because it has been shown that different membranes preferentially bind different ions. [50] Both Mg 2+ and Ca 2+ regularly stabilize membranes by the cross-linking of carboxylated and phosphorylated head groups of lipids. However, the envelope membrane of E. coli has also been shown to bind Na + , K + , Mn 2+ and Fe 3+ . The transport of ions is dependent on both the concentration gradient of the ion and the electric potential (ΔΨ) across the membrane, which will be affected by the charge on the membrane surface. For example, the specific binding of Mg 2+ to the chloroplast envelope has been implicated in a loss of photosynthetic efficiency by the blockage of K + uptake and the subsequent acidification of the chloroplast stroma. [36]

Proteins Edit

The Mg 2+ ion tends to bind only weakly to proteins (Ka ≤ 10 5 [50] ) and this can be exploited by the cell to switch enzymatic activity on and off by changes in the local concentration of Mg 2+ . Although the concentration of free cytoplasmic Mg 2+ is on the order of 1 mmol/L, the total Mg 2+ content of animal cells is 30 mmol/L [58] and in plants the content of leaf endodermal cells has been measured at values as high as 100 mmol/L (Stelzer et al., 1990), much of which buffered in storage compartments. The cytoplasmic concentration of free Mg 2+ is buffered by binding to chelators (e.g., ATP), but also, what is more important, by storage of Mg 2+ in intracellular compartments. The transport of Mg 2+ between intracellular compartments may be a major part of regulating enzyme activity. The interaction of Mg 2+ with proteins must also be considered for the transport of the ion across biological membranes.

Manganese Edit

In biological systems, only manganese (Mn 2+ ) is readily capable of replacing Mg 2+ , but only in a limited set of circumstances. Mn 2+ is very similar to Mg 2+ in terms of its chemical properties, including inner and outer shell complexation. Mn 2+ effectively binds ATP and allows hydrolysis of the energy molecule by most ATPases. Mn 2+ can also replace Mg 2+ as the activating ion for a number of Mg 2+ -dependent enzymes, although some enzyme activity is usually lost. [50] Sometimes such enzyme metal preferences vary among closely related species: For example, the reverse transcriptase enzyme of lentiviruses like HIV, SIV and FIV is typically dependent on Mg 2+ , whereas the analogous enzyme for other retroviruses prefers Mn 2+ .

Importance in drug binding Edit

An article [59] investigating the structural basis of interactions between clinically relevant antibiotics and the 50S ribosome appeared in Nature in October 2001. High-resolution X-ray crystallography established that these antibiotics associate only with the 23S rRNA of a ribosomal subunit, and no interactions are formed with a subunit's protein portion. The article stresses that the results show "the importance of putative Mg 2+ ions for the binding of some drugs".

By radioactive isotopes Edit

The use of radioactive tracer elements in ion uptake assays allows the calculation of km, Ki and Vmax and determines the initial change in the ion content of the cells. 28 Mg decays by the emission of a high-energy beta or gamma particle, which can be measured using a scintillation counter. However, the radioactive half-life of 28 Mg, the most stable of the radioactive magnesium isotopes, is only 21 hours. This severely restricts the experiments involving the nuclide. Also, since 1990, no facility has routinely produced 28 Mg, and the price per mCi is now predicted to be approximately US$30,000. [60] The chemical nature of Mg 2+ is such that it is closely approximated by few other cations. [61] However, Co 2+ , Mn 2+ and Ni 2+ have been used successfully to mimic the properties of Mg 2+ in some enzyme reactions, and radioactive forms of these elements have been employed successfully in cation transport studies. The difficulty of using metal ion replacement in the study of enzyme function is that the relationship between the enzyme activities with the replacement ion compared to the original is very difficult to ascertain. [61]

By fluorescent indicators Edit

A number of chelators of divalent cations have different fluorescence spectra in the bound and unbound states. [62] Chelators for Ca 2+ are well established, have high affinity for the cation, and low interference from other ions. Mg 2+ chelators lag behind and the major fluorescence dye for Mg 2+ (mag-fura 2 [63] ) actually has a higher affinity for Ca 2+ . [64] This limits the application of this dye to cell types where the resting level of Ca 2+ is < 1 μM and does not vary with the experimental conditions under which Mg 2+ is to be measured. Recently, Otten et al. (2001) have described work into a new class of compounds that may prove more useful, having significantly better binding affinities for Mg 2+ . [65] The use of the fluorescent dyes is limited to measuring the free Mg 2+ . If the ion concentration is buffered by the cell by chelation or removal to subcellular compartments, the measured rate of uptake will give only minimum values of km and Vmax.

By electrophysiology Edit

First, ion-specific microelectrodes can be used to measure the internal free ion concentration of cells and organelles. The major advantages are that readings can be made from cells over relatively long periods of time, and that unlike dyes very little extra ion buffering capacity is added to the cells. [66]

Second, the technique of two-electrode voltage-clamp allows the direct measurement of the ion flux across the membrane of a cell. [67] The membrane is held at an electric potential and the responding current is measured. All ions passing across the membrane contribute to the measured current.

Third, the technique of patch-clamp uses isolated sections of natural or artificial membrane in much the same manner as voltage-clamp but without the secondary effects of a cellular system. Under ideal conditions the conductance of individual channels can be quantified. This methodology gives the most direct measurement of the action of ion channels. [67]

By absorption spectroscopy Edit

Flame atomic absorption spectroscopy (AAS) determines the total magnesium content of a biological sample. [62] This method is destructive biological samples must be broken down in concentrated acids to avoid clogging the fine nebulising apparatus. Beyond this, the only limitation is that samples must be in a volume of approximately 2 mL and at a concentration range of 0.1 – 0.4 μmol/L for optimum accuracy. As this technique cannot distinguish between Mg 2+ already present in the cell and that taken up during the experiment, only content not uptaken can be quantified.

Inductively coupled plasma (ICP) using either the mass spectrometry (MS) or atomic emission spectroscopy (AES) modifications also allows the determination of the total ion content of biological samples. [68] These techniques are more sensitive than flame AAS and are capable of measuring the quantities of multiple ions simultaneously. However, they are also significantly more expensive.

The chemical and biochemical properties of Mg 2+ present the cellular system with a significant challenge when transporting the ion across biological membranes. The dogma of ion transport states that the transporter recognises the ion then progressively removes the water of hydration, removing most or all of the water at a selective pore before releasing the ion on the far side of the membrane. [69] Due to the properties of Mg 2+ , large volume change from hydrated to bare ion, high energy of hydration and very low rate of ligand exchange in the inner coordination sphere, these steps are probably more difficult than for most other ions. To date, only the ZntA protein of Paramecium has been shown to be a Mg 2+ channel. [70] The mechanisms of Mg 2+ transport by the remaining proteins are beginning to be uncovered with the first three-dimensional structure of a Mg 2+ transport complex being solved in 2004. [71]

The hydration shell of the Mg 2+ ion has a very tightly bound inner shell of six water molecules and a relatively tightly bound second shell containing 12–14 water molecules (Markham et al., 2002). Thus, it is presumed that recognition of the Mg 2+ ion requires some mechanism to interact initially with the hydration shell of Mg 2+ , followed by a direct recognition/binding of the ion to the protein. [60] Due to the strength of the inner sphere complexation between Mg 2+ and any ligand, multiple simultaneous interactions with the transport protein at this level might significantly retard the ion in the transport pore. Hence, it is possible that much of the hydration water is retained during transport, allowing the weaker (but still specific) outer sphere coordination.

In spite of the mechanistic difficulty, Mg 2+ must be transported across membranes, and a large number of Mg 2+ fluxes across membranes from a variety of systems have been described. [72] However, only a small selection of Mg 2+ transporters have been characterised at the molecular level.

Ligand ion channel blockade Edit

Magnesium ions (Mg 2+ ) in cellular biology are usually in almost all senses opposite to Ca 2+ ions, because they are bivalent too, but have greater electronegativity and thus exert greater pull on water molecules, preventing passage through the channel (even though the magnesium itself is smaller). Thus, Mg 2+ ions block Ca 2+ channels such as (NMDA channels) and have been shown to affect gap junction channels forming electrical synapses.

The previous sections have dealt in detail with the chemical and biochemical aspects of Mg 2+ and its transport across cellular membranes. This section will apply this knowledge to aspects of whole plant physiology, in an attempt to show how these processes interact with the larger and more complex environment of the multicellular organism.

Nutritional requirements and interactions Edit

Mg 2+ is essential for plant growth and is present in higher plants in amounts on the order of 80 μmol g −1 dry weight. [4] The amounts of Mg 2+ vary in different parts of the plant and are dependent upon nutritional status. In times of plenty, excess Mg 2+ may be stored in vascular cells (Stelzer et al., 1990 [34] and in times of starvation Mg 2+ is redistributed, in many plants, from older to newer leaves. [4] [73]

Mg 2+ is taken up into plants via the roots. Interactions with other cations in the rhizosphere can have a significant effect on the uptake of the ion.(Kurvits and Kirkby, 1980 [74] The structure of root cell walls is highly permeable to water and ions, and hence ion uptake into root cells can occur anywhere from the root hairs to cells located almost in the centre of the root (limited only by the Casparian strip). Plant cell walls and membranes carry a great number of negative charges, and the interactions of cations with these charges is key to the uptake of cations by root cells allowing a local concentrating effect. [75] Mg 2+ binds relatively weakly to these charges, and can be displaced by other cations, impeding uptake and causing deficiency in the plant.

Within individual plant cells, the Mg 2+ requirements are largely the same as for all cellular life Mg 2+ is used to stabilise membranes, is vital to the utilisation of ATP, is extensively involved in the nucleic acid biochemistry, and is a cofactor for many enzymes (including the ribosome). Also, Mg 2+ is the coordinating ion in the chlorophyll molecule. It is the intracellular compartmentalisation of Mg 2+ in plant cells that leads to additional complexity. Four compartments within the plant cell have reported interactions with Mg 2+ . Initially, Mg 2+ will enter the cell into the cytoplasm (by an as yet unidentified system), but free Mg 2+ concentrations in this compartment are tightly regulated at relatively low levels (≈2 mmol/L) and so any excess Mg 2+ is either quickly exported or stored in the second intracellular compartment, the vacuole. [76] The requirement for Mg 2+ in mitochondria has been demonstrated in yeast [77] and it seems highly likely that the same will apply in plants. The chloroplasts also require significant amounts of internal Mg 2+ , and low concentrations of cytoplasmic Mg 2+ . [78] [79] In addition, it seems likely that the other subcellular organelles (e.g., Golgi, endoplasmic reticulum, etc.) also require Mg 2+ .

Distributing magnesium ions within the plant Edit

Once in the cytoplasmic space of root cells Mg 2+ , along with the other cations, is probably transported radially into the stele and the vascular tissue. [80] From the cells surrounding the xylem the ions are released or pumped into the xylem and carried up through the plant. In the case of Mg 2+ , which is highly mobile in both the xylem and phloem, [81] the ions will be transported to the top of the plant and back down again in a continuous cycle of replenishment. Hence, uptake and release from vascular cells is probably a key part of whole plant Mg 2+ homeostasis. Figure 1 shows how few processes have been connected to their molecular mechanisms (only vacuolar uptake has been associated with a transport protein, AtMHX).

The diagram shows a schematic of a plant and the putative processes of Mg 2+ transport at the root and leaf where Mg 2+ is loaded and unloaded from the vascular tissues. [4] Mg 2+ is taken up into the root cell wall space (1) and interacts with the negative charges associated with the cell walls and membranes. Mg 2+ may be taken up into cells immediately (symplastic pathway) or may travel as far as the Casparian band (4) before being absorbed into cells (apoplastic pathway 2). The concentration of Mg 2+ in the root cells is probably buffered by storage in root cell vacuoles (3). Note that cells in the root tip do not contain vacuoles. Once in the root cell cytoplasm, Mg 2+ travels toward the centre of the root by plasmodesmata, where it is loaded into the xylem (5) for transport to the upper parts of the plant. When the Mg 2+ reaches the leaves it is unloaded from the xylem into cells (6) and again is buffered in vacuoles (7). Whether cycling of Mg 2+ into the phloem occurs via general cells in the leaf (8) or directly from xylem to phloem via transfer cells (9) is unknown. Mg 2+ may return to the roots in the phloem sap.

When a Mg 2+ ion has been absorbed by a cell requiring it for metabolic processes, it is generally assumed that the ion stays in that cell for as long as the cell is active. [4] In vascular cells, this is not always the case in times of plenty, Mg 2+ is stored in the vacuole, takes no part in the day-to-day metabolic processes of the cell (Stelzer et al., 1990), and is released at need. But for most cells it is death by senescence or injury that releases Mg 2+ and many of the other ionic constituents, recycling them into healthy parts of the plant. In addition, when Mg 2+ in the environment is limiting, some species are able to mobilise Mg 2+ from older tissues. [73] These processes involve the release of Mg 2+ from its bound and stored states and its transport back into the vascular tissue, where it can be distributed to the rest of the plant. In times of growth and development, Mg 2+ is also remobilised within the plant as source and sink relationships change. [4]

The homeostasis of Mg 2+ within single plant cells is maintained by processes occurring at the plasma membrane and at the vacuole membrane (see Figure 2). The major driving force for the translocation of ions in plant cells is ΔpH. [82] H + -ATPases pump H + ions against their concentration gradient to maintain the pH differential that can be used for the transport of other ions and molecules. H + ions are pumped out of the cytoplasm into the extracellular space or into the vacuole. The entry of Mg 2+ into cells may occur through one of two pathways, via channels using the ΔΨ (negative inside) across this membrane or by symport with H + ions. To transport the Mg 2+ ion into the vacuole requires a Mg 2+ /H + antiport transporter (such as AtMHX). The H + -ATPases are dependent on Mg 2+ (bound to ATP) for activity, so that Mg 2+ is required to maintain its own homeostasis.

A schematic of a plant cell is shown including the four major compartments currently recognised as interacting with Mg 2+ . H + -ATPases maintain a constant ΔpH across the plasma membrane and the vacuole membrane. Mg 2+ is transported into the vacuole using the energy of ΔpH (in A. thaliana by AtMHX). Transport of Mg 2+ into cells may use either the negative ΔΨ or the ΔpH. The transport of Mg 2+ into mitochondria probably uses ΔΨ as in the mitochondria of yeast, and it is likely that chloroplasts take Mg 2+ by a similar system. The mechanism and the molecular basis for the release of Mg 2+ from vacuoles and from the cell is not known. Likewise, the light-regulated Mg 2+ concentration changes in chloroplasts are not fully understood, but do require the transport of H + ions across the thylakoid membrane.

Magnesium, chloroplasts and photosynthesis Edit

Mg 2+ is the coordinating metal ion in the chlorophyll molecule, and in plants where the ion is in high supply about 6% of the total Mg 2+ is bound to chlorophyll. [4] [83] [84] Thylakoid stacking is stabilised by Mg 2+ and is important for the efficiency of photosynthesis, allowing phase transitions to occur. [85]

Mg 2+ is probably taken up into chloroplasts to the greatest extent during the light-induced development from proplastid to chloroplast or etioplast to chloroplast. At these times, the synthesis of chlorophyll and the biogenesis of the thylakoid membrane stacks absolutely require the divalent cation. [86] [87]

Whether Mg 2+ is able to move into and out of chloroplasts after this initial developmental phase has been the subject of several conflicting reports. Deshaies et al. (1984) found that Mg 2+ did move in and out of isolated chloroplasts from young pea plants, [88] but Gupta and Berkowitz (1989) were unable to reproduce the result using older spinach chloroplasts. [89] Deshaies et al. had stated in their paper that older pea chloroplasts showed less significant changes in Mg 2+ content than those used to form their conclusions. The relative proportion of immature chloroplasts present in the preparations may explain these observations.

The metabolic state of the chloroplast changes considerably between night and day. During the day, the chloroplast is actively harvesting the energy of light and converting it into chemical energy. The activation of the metabolic pathways involved comes from the changes in the chemical nature of the stroma on the addition of light. H + is pumped out of the stroma (into both the cytoplasm and the lumen) leading to an alkaline pH. [90] [91] Mg 2+ (along with K + ) is released from the lumen into the stroma, in an electroneutralisation process to balance the flow of H + . [92] [93] [94] [95] Finally, thiol groups on enzymes are reduced by a change in the redox state of the stroma. [96] Examples of enzymes activated in response to these changes are fructose 1,6-bisphosphatase, sedoheptulose bisphosphatase and ribulose-1,5-bisphosphate carboxylase. [4] [53] [96] During the dark period, if these enzymes were active a wasteful cycling of products and substrates would occur.

Two major classes of the enzymes that interact with Mg 2+ in the stroma during the light phase can be identified. [53] Firstly, enzymes in the glycolytic pathway most often interact with two atoms of Mg 2+ . The first atom is as an allosteric modulator of the enzymes' activity, while the second forms part of the active site and is directly involved in the catalytic reaction. The second class of enzymes includes those where the Mg 2+ is complexed to nucleotide di- and tri-phosphates (ADP and ATP), and the chemical change involves phosphoryl transfer. Mg 2+ may also serve in a structural maintenance role in these enzymes (e.g., enolase).

Magnesium stress Edit

Plant stress responses can be observed in plants that are under- or over-supplied with Mg 2+ . The first observable signs of Mg 2+ stress in plants for both starvation and toxicity is a depression of the rate of photosynthesis, it is presumed because of the strong relationships between Mg 2+ and chloroplasts/chlorophyll. In pine trees, even before the visible appearance of yellowing and necrotic spots, the photosynthetic efficiency of the needles drops markedly. [73] In Mg 2+ deficiency, reported secondary effects include carbohydrate immobility, loss of RNA transcription and loss of protein synthesis. [97] However, due to the mobility of Mg 2+ within the plant, the deficiency phenotype may be present only in the older parts of the plant. For example, in Pinus radiata starved of Mg 2+ , one of the earliest identifying signs is the chlorosis in the needles on the lower branches of the tree. This is because Mg 2+ has been recovered from these tissues and moved to growing (green) needles higher in the tree. [73]

A Mg 2+ deficit can be caused by the lack of the ion in the media (soil), but more commonly comes from inhibition of its uptake. [4] Mg 2+ binds quite weakly to the negatively charged groups in the root cell walls, so that excesses of other cations such as K + , NH4 + , Ca 2+ , and Mn 2+ can all impede uptake.(Kurvits and Kirkby, 1980 [74] In acid soils Al 3+ is a particularly strong inhibitor of Mg 2+ uptake. [98] [99] The inhibition by Al 3+ and Mn 2+ is more severe than can be explained by simple displacement, hence it is possible that these ions bind to the Mg 2+ uptake system directly. [4] In bacteria and yeast, such binding by Mn 2+ has already been observed. Stress responses in the plant develop as cellular processes halt due to a lack of Mg 2+ (e.g. maintenance of ΔpH across the plasma and vacuole membranes). In Mg 2+ -starved plants under low light conditions, the percentage of Mg 2+ bound to chlorophyll has been recorded at 50%. [100] Presumably, this imbalance has detrimental effects on other cellular processes.

Mg 2+ toxicity stress is more difficult to develop. When Mg 2+ is plentiful, in general the plants take up the ion and store it (Stelzer et al., 1990). However, if this is followed by drought then ionic concentrations within the cell can increase dramatically. High cytoplasmic Mg 2+ concentrations block a K + channel in the inner envelope membrane of the chloroplast, in turn inhibiting the removal of H + ions from the chloroplast stroma. This leads to an acidification of the stroma that inactivates key enzymes in carbon fixation, which all leads to the production of oxygen free radicals in the chloroplast that then cause oxidative damage. [101]


Consider Why Viruses Are Not A Living Organism?

Viruses are not living things because viruses are complex assemblies of molecules, including proteins, lipids, nucleic acids, and carbohydrates, but on their own, they can do nothing until they enter a living cell. Without cells, the virus is unable to do anything that’s why it is a non-living thing.

Do you know viruses are different from bacteria? Yes, virus and bacteria both are different, but both make us sick. Bacteria are small and single-celled, but they are living organisms that do not depend on a host cell to replicate. Because of these variations, bacterial and viral infections treated very differently. The antibiotics are only necessary against bacteria, not viruses.

Respiratory is one of the viral diseases which commonly affect the upper or lower parts of your respiratory tract. Some of the examples of respiratory diseases are:

  • flu
  • common cold
  • respiratory syncytial virus infection
  • adenovirus infection
  • parainfluenza virus infection
  • severe acute respiratory syndrome (SARS)

What are non-living beings?

Everything that does not meet the requirements of “life” is considered as a non-living, inanimate or inert being.

Natural objects and artificial objects

Natural non-living objects are those created by the physical and chemical forces of nature, such as rocks, clouds, oceans, mountains, among others.

The artificial nonliving objects are those creations of human beings, such as mobile, bridges, roads, dishes and clothes.


Further classification

Based on the information above, we can confidently categorise earthworms as living things as they carry out all seven life processes.

It is now possible to classify them further into a series of hierarchical categories: kingdom, phylum, class, order, family, genus and species. Classifying living things into these categories is an important way for scientists to show how living things are related to each other. Most scientists classify living things into one of the following six kingdoms.

  • Bacteria are single-celled microorganisms that don’t have a nuclear membrane.
  • Protozoans are single-celled organisms that are generally much larger than bacteria. They may be autotrophic or heterotrophic.
  • Chromists are a diverse group of plant-like organisms and range from very small to very large. They are found in almost all environments.
  • Fungi are multicellular and rely on breaking down organic material as they are not able to make their own food.
  • Plants are multicellular and autotrophic – they use photosynthesis to produce food using sunlight.
  • Animals are multicellular. They are heterotrophic and rely on other organisms for food.

Which kingdom do you think earthworms belong to?


Summary

In the first part of photosynthesis, the light-dependent reaction, pigment molecules absorb energy from sunlight. The most common and abundant pigment is chlorophyll a. A photon strikes photosystem II to initiate photosynthesis. Energy travels through the electron transport chain, which pumps hydrogen ions into the thylakoid space. This forms an electrochemical gradient. The ions flow through ATP synthase from the thylakoid space into the stroma in a process called chemiosmosis to form molecules of ATP, which are used for the formation of sugar molecules in the second stage of photosynthesis. Photosystem I absorbs a second photon, which results in the formation of an NADPH molecule, another energy carrier for the Calvin cycle reactions.


Micronutrient Information Center

Chlorophyll is the pigment that gives plants and algae their green color. Plants use chlorophyll to trap light needed for photosynthesis (1). The basic structure of chlorophyll is a porphyrin ring similar to that of heme in hemoglobin, although the central atom in chlorophyll is magnesium instead of iron. The long hydrocarbon (phytol) tail attached to the porphyrin ring makes chlorophyll fat-soluble and insoluble in water. Two different types of chlorophyll (chlorophyll a and chlorophyll b) are found in plants (Figure 1). The small difference in one of the side chains allows each type of chlorophyll to absorb light at slightly different wavelengths. Chlorophyllin is a semi-synthetic mixture of sodium copper salts derived from chlorophyll (2, 3). During the synthesis of chlorophyllin, the magnesium atom at the center of the ring is replaced with copper and the phytol tail is lost. Unlike natural chlorophyll, chlorophyllin is water-soluble. Although the content of different chlorophyllin mixtures may vary, two compounds commonly found in commercial chlorophyllin mixtures are trisodium copper chlorin e6 and disodium copper chlorin e4 (Figure 2).

Metabolism and Bioavailability

Little is known about the bioavailability and metabolism of chlorophyll or chlorophyllin. The lack of toxicity attributed to chlorophyllin led to the belief that it was poorly absorbed (4). However, significant amounts of copper chlorin e4 were measured in the plasma of humans taking chlorophyllin tablets in a controlled clinical trial, indicating that it is absorbed. More research is needed to understand the bioavailability and metabolism of natural chlorophylls and chlorin compounds in synthetic chlorophyllin.

Biological Activities

Complex formation with other molecules

Chlorophyll and chlorophyllin are able to form tight molecular complexes with certain chemicals known or suspected to cause cancer, including polycyclic aromatic hydrocarbons found in tobacco smoke (5), some heterocyclic amines found in cooked meat (6), and aflatoxin-B1 (7). The binding of chlorophyll or chlorophyllin to these potential carcinogens may interfere with gastrointestinal absorption of potential carcinogens, reducing the amount that reaches susceptible tissues (8). A recently completed study by Linus Pauling Institute investigator Professor George S. Bailey showed that chlorophyllin and chlorophyll were equally effective at blocking uptake of aflatoxin-B1 in humans, using accelerator mass spectrometry to track an ultra-low dose of the carcinogen (C Jubert et al., manuscript submitted).

Antioxidant effects

Chlorophyllin can neutralize several physically relevant oxidants in vitro (9, 10), and limited data from animal studies suggest that chlorophyllin supplementation may decrease oxidative damage induced by chemical carcinogens and radiation (11, 12).

Modification of the metabolism and detoxification of carcinogens

To initiate the development of cancer, some chemicals (procarcinogens) must first be metabolized to active carcinogens that are capable of damaging DNA or other critical molecules in susceptible tissues. Since enzymes in the cytochrome P450 family are required for the activation of some procarcinogens, inhibition of cytochrome P450 enzymes may decrease the risk of some types of chemically induced cancers. In vitro studies indicate that chlorophyllin may decrease the activity of cytochrome P450 enzymes (5, 13). Phase II biotransformation enzymes promote the elimination of potentially harmful toxins and carcinogens from the body. Limited data from animal studies indicate that chlorophyllin may increase the activity of the phase II enzyme, quinone reductase (14).

Therapeutic effects

A recent study showed that human colon cancer cells undergo cell cycle arrest after treatment with chlorophyllin (15). The mechanism involved inhibition of ribonucleotide reductase activity. Ribonucleotide reductase plays a pivotal role in DNA synthesis and repair, and is a target of currently used cancer therapeutic agents, such as hydroxyurea (15). This provides a potential new avenue for chlorophyllin in the clinical setting, sensitizing cancer cells to DNA damaging agents.

Disease Prevention

Aflatoxin-associated liver cancer

Aflatoxin-B1 (AFB1) a liver carcinogen produced by certain species of fungus, is found in moldy grains and legumes, such as corn, peanuts, and soybeans (2, 8). In hot, humid regions of Africa and Asia with improper grain storage facilities, high levels of dietary AFB1 are associated with increased risk of hepatocellular carcinoma. Moreover, the combination of hepatitis B infection and high dietary AFB1 exposure increases the risk of hepatocellular carcinoma still further. In the liver, AFB1 is metabolized to a carcinogen capable of binding DNA and causing mutations. In animal models of AFB1-induced liver cancer, administration of chlorophyllin at the same time as dietary AFB1 exposure significantly reduces AFB1-induced DNA damage in the livers of rainbow trout and rats (16-18), and dose-dependently inhibits the development of liver cancer in trout (19). One rat study found that chlorophyllin did not protect against aflatoxin-induced liver damage when given after tumor initiation (20). In addition, a recent study reported that natural chlorophyll inhibited AFB1-induced liver cancer in the rat (18).

Because of the long time period between AFB1 exposure and the development of cancer in humans, an intervention trial might require as long as 20 years to determine whether chlorophyllin supplementation can reduce the incidence of hepatocellular carcinoma in people exposed to high levels of dietary AFB1. However, a biomarker of AFB1-induced DNA damage (AFB1-N 7 -guanine) can be measured in the urine, and high urinary levels of AFB1-N 7 -guanine have been associated with significantly increased risk of developing hepatocellular carcinoma (21). In order to determine whether chlorophyllin could decrease AFB1-induced DNA damage in humans, a randomized, placebo-controlled intervention trial was conducted in 180 adults residing in a region in China where the risk of hepatocellular carcinoma is very high due to unavoidable dietary AFB1 exposure and a high prevalence of chronic hepatitis B infection (22). Participants took either 100 mg of chlorophyllin or a placebo before meals three times daily. After 16 weeks of treatment, urinary levels of AFB1-N 7 -guanine were 55% lower in those taking chlorophyllin than in those taking the placebo, suggesting that chlorophyllin supplementation before meals can substantially decrease AFB1-induced DNA damage. Although a reduction in hepatocellular carcinoma has not yet been demonstrated in humans taking chlorophyllin, scientists are hopeful that chlorophyllin supplementation will provide some protection to high-risk populations with unavoidable, dietary AFB1 exposure (8).

It is not known whether chlorophyllin will be useful in the prevention of cancers in people who are not exposed to significant levels of dietary AFB1, as is the case for most people living in the US. Many questions remain to be answered regarding the exact mechanisms of cancer prevention by chlorophyllin, the implications for the prevention of other types of cancer, and the potential for natural chlorophylls in the diet to provide cancer protection. Scientists from the Linus Pauling Institute’s Cancer Chemoprotection Program (CCP) are actively pursuing these research questions.

Therapeutic Uses of Chlorophyllin

Internal deodorant

Observations in the 1940s and 1950s that topical chlorophyllin had deodorizing effects on foul-smelling wounds led clinicians to administer chlorophyllin orally to patients with colostomies and ileostomies in order to control fecal odor (23). While early case reports indicated that chlorophyllin doses of 100-200 mg/day were effective in reducing fecal odor in ostomy patients (24, 25), at least one placebo-controlled trial found that 75 mg of oral chlorophyllin three times daily was no more effective than placebo in decreasing fecal odor assessed by colostomy patients (26). Several case reports have been published indicating that oral chlorophyllin (100-300 mg/day) decreased subjective assessments of urinary and fecal odor in incontinent patients (23, 27). Trimethylaminuria is a hereditary disorder characterized by the excretion of trimethylamine, a compound with a “fishy” or foul odor. A recent study in a small number of Japanese patients with trimethylaminuria found that oral chlorophyllin (60 mg three times daily) for three weeks significantly decreased urinary trimethylamine concentrations (28).

Wound healing

Research in the 1940s indicating that chlorophyllin slowed the growth of certain anaerobic bacteria in the test tube and accelerated the healing of experimental wounds in animals led to the use of topical chlorophyllin solutions and ointments in the treatment of persistent open wounds in humans (29). During the late 1940s and 1950s, a series of largely uncontrolled studies in patients with slow-healing wounds, such as vascular ulcers and pressure (decubitus) ulcers, reported that the application of topical chlorophyllin promoted healing more effectively than other commonly used treatments (30, 31). In the late 1950s, chlorophyllin was added to papain and urea-containing ointments used for the chemical debridement of wounds in order to reduce local inflammation, promote healing, and control odor (23). Chlorophyllin-containing papain/urea ointments are still available in the US by prescription (32). Several studies have reported that such ointments are effective in wound healing (33). Recently, a spray formulation of the papain/urea/chlorophyllin therapy has become available (34).

Sources

Chlorophylls

Chlorophylls are the most abundant pigments in plants. Dark green, leafy vegetables like spinach are rich sources of natural chlorophylls. The chlorophyll contents of selected vegetables are presented in Table 1 (35).

Table 1. Chlorophyll Content of Selected Raw Vegetables
Food Serving Chlorophyll (mg)
Spinach 1 cup 23.7
Parsley ½ cup 19.0
Cress, garden 1 cup 15.6
Green beans 1 cup 8.3
Arugula 1 cup 8.2
Leeks 1 cup 7.7
Endive 1 cup 5.2
Sugar peas 1 cup 4.8
Chinese cabbage 1 cup 4.1

Supplements

Chlorophyll

Green algae like chlorella are often marketed as supplemental sources of chlorophyll. Because natural chlorophyll is not as stable as chlorophyllin and is much more expensive, most over-the-counter chlorophyll supplements actually contain chlorophyllin.

Chlorophyllin

Oral preparations of sodium copper chlorophyllin (also called chlorophyllin copper complex) are available in supplements and as an over-the-counter drug (Derifil) used to reduce odor from colostomies or ileostomies or to reduce fecal odor due to incontinence (36). Sodium copper chlorophyllin may also be used as a color additive in foods, drugs, and cosmetics (37). Oral doses of 100-300 mg/day in three divided doses have been used to control fecal and urinary odor (see Therapeutic Uses of Chlorophyllin).

Safety

Natural chlorophylls are not known to be toxic, and no toxic effects have been attributed to chlorophyllin despite more than 50 years of clinical use in humans (8, 23, 29). When taken orally, chlorophyllin may cause green discoloration of urine or feces, or yellow or black discoloration of the tongue (38). There have also been occasional reports of diarrhea related to oral chlorophyllin use. When applied topically to wounds, chlorophyllin has been reported to cause mild burning or itching in some cases (39). Oral chlorophyllin may result in false positive results on guaiac card tests for occult blood (40). Since the safety of chlorophyll or chlorophyllin supplements has not been tested in pregnant or lactating women, they should be avoided during pregnancy and lactation.

Authors and Reviewers

Originally written in 2004 by:
Jane Higdon, Ph.D.
Linus Pauling Institute
Oregon State University

Updated in December 2005 by:
Jane Higdon, Ph.D.
Linus Pauling Institute
Oregon State University

Updated in June 2009 by:
Victoria J. Drake, Ph.D.
Linus Pauling Institute
Oregon State University

Reviewed in June 2009 by:
Roderick H. Dashwood, Ph.D.
Director, Cancer Chemoprotection Program, Linus Pauling Institute
Professor of Environmental & Molecular Toxicology
Leader, Environmental Mutagenesis & Carcinogenesis Core, Environmental Health Sciences Center
Oregon State University

Copyright 2004-2021 Linus Pauling Institute

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