What is chlorophyll in plants? Functions and Structure

What is chlorophyll? chlorophyll is commonly related to green plants as the molecule or pigment that makes plants have a green color. In this article, chlorophyll will be explained with respect to the types, its structure, and ultimately the benefits of chlorophyll in humans and plants.

Chlorophyll definition

Chlorophyll is defined as a molecule produced by plants, algae, and cyanobacteria that aids in the conversion of light energy into chemical bonds.

What is chlorophyll?

Chlorophyll is a pigment or molecule that absorbs some wavelengths of light while reflecting others. It is also the green pigment that is responsible for the green color in plants, algae, and cyanobacteria.

Chlorophyll is the most abundant naturally occurring pigment on Earth and it is found in plants and some microorganisms (such as cyanobacteria) which plays an important role in the conversion of solar energy to chemical energy, a process known as photosynthesis. Besides photosynthesis, chlorophylls are used for a range of commercial activities in agriculture and the food industry.

Structure of chlorophyll

Chlorophylls, like heme groups, are porphyrins found in plants and as such, they are tetrapyrroles with a metal ion at their core. Unlike heme groups, which contain iron (Fe) at their core, chlorophyll contains magnesium (Mg) as its metal ion.

The chlorophyll structure is made up of the following chemical components listed below.

  • A porphyrin (tetrapyrrole) nucleus known as the head containing a chelated magnesium atom. Also, the porphyrin head of the structure is made up of four pyrrole rings with nitrogen arranged in a ring.
  • Hydrocarbon chains linked by a carboxylic acid group known as the tail. Meaning that the tail part of the structure is made up of a long hydrocarbon chain.

Location of chlorophyll in the chloroplast

The pigment (chlorophyll) is found in photosystems I and II of chloroplasts, within the thylakoid membrane which means that chlorophylls are membrane-bound pigments in plants. This answers the question of where chlorophyll is located within the chloroplast.

However, there are some prokaryotes capable of photosynthesis, such as cyanobacteria, and in these prokaryotes, the chloroplast (along with other membrane-bound organelles) is absent. This means that the pigment is not encased in a membrane as seen in eukaryotic cells.

What does chlorophyll do?

One of the functions of chlorophyll is that it aids plants in absorbing energy from the sun during the photosynthesis process.

Chlorophyll function

  1. Chlorophyll in photosynthesis
  2. Chlorophyll in the production of oxygen

The above-mentioned are the most important functions of chlorophyll with regards to plants and the ecosystem.

Chlorophyll in photosynthesis

Chlorophyll function in photosynthesis is undoubtedly amongst the most crucial process on our planet because it uses solar energy to transform carbon dioxide and water into organic molecules, which not only allow plants to continue growing and reproducing but also provide food for numerous animals and humans.

The photosynthesis process undergoes two phases namely the light/energy-harvesting phase (when chlorophyll catches light energy) and the carbon reduction phase are the two primary phases of photosynthesis (the Calvin cycle).

Chlorophyll in the production of oxygen

Photosynthesis produces oxygen as a byproduct and plants can utilize this oxygen for cellular respiration, but they also discharge a bulk portion of the oxygen into the atmosphere. This discharged oxygen into the atmosphere allows many non-plants to undergo respiration as well, thereby supporting life on Earth.

Oxygen is produced in the first part of the light cycle of photosynthesis as water molecules are split by plants to produce electrons, hydrogen ions, and diatomic oxygen (O2). The electron transport cycle, which promotes ATP generation, is fueled by electrons as oxygen is discharged into the atmosphere.

Chlorophyll benefits

  • The initial benefit of chlorophyll is sugar, which is created by the chlorophyll-driven ATP process. Plants form the foundation of the food chain as primary producers and the sugars that plants produce are essential for the survival of all other species in the food chain. Even though apex predators in a food chain may never consume a single plant, they are however affected because they eat herbivores that eat exclusively plants and gain weight and muscle mass by digesting and using plant nutrients. Without chlorophyll, these nutrients would not be able to accumulate in nature for herbivores to eat and for the food web to continue.
  • The second advantage is based on the fact that all species enjoy oxygen which is provided because of chlorophyll. While chlorophyll and the complex of proteins with which it is connected can not make oxygen directly, they do however transfer electrons to molecules like ATP and NADPH, which can store energy in bonds. The transfers of electron causes water molecules to be divided as a result of the demand for electrons to drive this process, resulting in the creation of oxygen. This oxygen is then released into the air and all of the oxygen in the atmosphere is produced by plants, algae, and cyanobacteria. All other animals, as well as the majority of plants, require this oxygen to survive.

Apart from its ecological value, chlorophyll may also be beneficial to human health and well-being. For example, alternative medicine is made from semi-synthetic chlorophyll derivatives (liquid chlorophyll or chlorophyll water) and a chlorophyll derivative that is commonly used as a dietary supplement is sodium/copper chlorophyllin (and a food colorant).

The following are some of its applications:

  • Tissue repair: chlorophyll aids wound healing and inflammation reduction. It appears to hasten healing by inhibiting bacterial development.
  • Chlorophyll is also utilized as a natural deodorant to help neutralize the stink of foul breath, urine, or feces. People who suffer fecal incontinence or who have undergone a colostomy use it.
  • Detoxification: It have detoxifying properties as well as anti-cancer properties.

Types of chlorophyll

  • Chlorophyll a and b
  • Chlorophyll c
  • Chlorophyll d
  • Chlorophyll e
  • Chlorophyll f
These are the structural formulas of the types of chlorophyll. Which aids in explaining what is chlorophyll.
Structural formular of the types of chlorophyll. Image Source: David Richfield (Chlorophyll a,b,c1,c2,c3) and Yikrazuul (Chlorophyll d,f).

Chlorophyll a and b

Chlorophyll a is a pigment that is found and required for all photosynthetic organisms, while chlorophyll b is not found in all photosynthetic organisms. Rather it acts as an auxiliary pigment to chlorophyll a, despite being one of the most important chlorophyll pigments.

Chlorophyll b absorbs blue light more than chlorophyll a and thus broadens the spectrum of light absorbed. Plants with chlorophyll b convert a greater proportion of solar energy to chemical energy than plants without the pigment. The presence of chlorophyll b is one of the adaptive strategies that allows plants to absorb a wider range of light wavelengths in environments with less sunlight.

Chlorophyll a (Chl a) is involved not only in light-harvesting complexes but also in reactions that occur in reaction centers of all plants capable of oxygenic photosynthesis. While chlorophyll b (Chl b) serves as a complement pigment, harvesting light at a 1:3 ratio (to Chl a).

Chlorophyll a and b have a tadpole-like structure, the structural difference between the two is due to a single atom on the third carbon in the side chain at the porphyrin ring (head of the structure). The pigment chlorophyll b is found in antenna complexes of photosystem II (light-harvesting complexes) in plants and microorganisms, where it accounts for approximately 50% of chlorophyll.

Chlorophyll c

Chlorophyll c (Chl c) is found in a variety of organisms, including nine types of algae (chromophyte algae) and two types of prokaryotes. This chlorophyll may co-occur with other pigments depending on the organism (e.g. Chl a and carotenoids). It also has a different structure than some of the other chlorophylls, for example, chlorophyll c has been demonstrated to be Mg-phytoporphyrins while the other forms of chlorophyll are Mg-chlorins.

The structure of this pigment contains propenoic acid (a transacrylic acid) at the C-17 ring, which replaces the propionic acid side chain found in chlorophylls a and b. In terms of structure, the polar forms of chlorophyll c are known as protochlorophyllides (precursors of chlorophyll). However, because of their ability to absorb light, they are classified as chlorophyll.

Chlorophyll d

Chlorophyll d is a minor pigment found in red algae and some microorganisms (cyanobacteria) that are involved in the capture of the red spectrum of light (far end spectrum of red light).

Chl d differs from other forms of chlorophyll in terms of structure. For example, chlorophyll d differs from chlorophyll a such that it contains a formyl group (Here, the formyl group takes the place of a C3-vinyl group located on the chemical structure of Chl a).

Chlorophyll e

This is a rare type of accessory pigment isolated from only a few algal species, including some golden algae.

Chlorophyll f

Chlorophyll f is the most recently discovered form of chlorophyll and unlike the other pigments found in plants and microorganisms, Chl f is found in cyanobacteria found in wetlands. Chl f, like Chl a and Chl c, has been shown to be an accessory pigment in the antenna system of cyanobacteria.

One of the most significant advantages of the pigment over others is its ability to absorb large amounts of near-infrared light when compared to other forms of chlorophyll. As a result, organisms with this pigment have a competitive advantage because energy is harvested from a different light wavelength than other organisms that rely on the usual wavelength of light for photosynthesis.

Summary on chlorophyll types

Types
Features
Wavelength spectrum absorption
Examples
Chlorophyll a
The most important light-harvesting pigment found in all photosynthetic organisms.
Molecular formula: C55H72O5N4Mg
400-450 nm and 650-700 nm
higher plants, red algae, green algae
Chlorophyll b
It acts as a light-harvesting pigment, transmitting light excitation to chlorophyll a.
C55H70O6N4Mg is the molecular formula.
450-500 nm and 600-650 nm
higher plants, green algae
Chlorophyll c
A pigment found in certain marine algae. Molecular formula: C35H28O5N4Mg
447–452 nm
diatoms, dinoflagellates, brown algae
Chlorophyll d
The chlorophyll found in photosynthetic organisms that live in moderately deep water.
Molecular formula: C54H70O6N4Mg
Infrared light
red algae, cyanobacteria (blue-green algae
Chlorophyll e
A rare type of accessory pigment isolated from only a few algal species, including some golden algae. There is insufficient information about this type of chlorophyll, including its chemical structure and molecular formula.
Tribonema bombycinum and Vaucheria hamata
Chlorophyll f
The form of chlorophyll found in aquatic organisms that allows for the absorption of near-infrared light. Molecular formula C55H70O6N4Mg
Near-infrared light
Cyanobacteria
A table showing the types, features, and examples of chlorophyll.

Green chlorophyll

Chlorophyll is responsible for the green color of plants (and some organisms). To understand why plants appear green to the human eye, it is important to remember that, unlike some other animal groups, humans are trichromats, which means they interpret colors based on the ratio of three primary wavelengths of visible light (red, green, and blue light).

Chlorophyll, which is green in color, can absorb red and blue light within the visible spectrum of light in nature. But this is not the case with green light, because it is reflected rather than absorbed. This results in the brain interpreting the reflected light on the plant as a green-colored plant.

In addition, chlorophyll production ceases as plants prepare for winter (in the fall), and any chlorophyll that is present also degrades, causing the green color to fade. Plants may become more yellow/orange/reddish in color as a result of this decomposition and the presence of other pigments (e.g., anthocyanin in some plants). The mixing of chlorophyll residues with the other pigments causes this change in color.

Chlorophyll examples

  • Plants
  • Algae
  • Cyanobacteria

Plants

Chlorophyll is the most abundant photosynthetic pigment in plants and in order to absorb light energy, the chloroplast in the plant cell usually contains a large number of chlorophyll pigments. Some plants produce a green shoot all the way through, examples are those herbs with abundant chlorophyll pigments not only in the leaves but also on the stems.

There are also some plants that will eventually develop thick brownish stems known as bark, even though their leaves remain green and serve as the primary photosynthetic organ of the plant. While some trees remain “evergreen” by bearing leaves all season, others shed their leaves at the end of the growing season and they are known as “deciduous” trees.

Deciduous trees degrade their chlorophylls, causing their leaves to change color to yellow, purple, red, or brown. As an adaptation to the winter or dry season, they tend to transfer nutrients from the leaves to the stems and roots after the leaves have fallen. Then, at the end of the winter or dry season, they regrow their chlorophyll-rich leaves to collect light for photosynthesis.

Algae

Chlorophylls are also found inside the chloroplasts of algae as the majority of them are capable of photosynthesis. Photosynthetic algae are a major biological source of oxygen in the atmosphere and they are a diverse group of microscopic and macroscopic autotrophs that live in a variety of bodies of water. While the majority of them live in water, some can also be found in terrestrial environments such as moist soil, trees, and rocks. While others live in lichens and form symbiotic relationships with specific fungal species.

Cyanobacteria

The presence of chlorophyll in cyanobacteria makes them a good example of photosynthetic prokaryotes. Although cyanobacteria have thylakoid membranes, they are not organized within organelles. Rather, thylakoids are infoldings of the cyanobacterial cell’s plasma membrane and in contrast to plant thylakoids, which are arranged in stacks or discs (granum), cyanobacterial thylakoids are arranged in concentric shells.

Liquid chlorophyll

Liquid chlorophyll is a liquefied chlorophyll extract derived from various green plants. It is obtained by juicing green plants such as wheatgrass or by taking supplements. Because liquid chlorophyll is liposoluble and does not dissolve in water, it is only minimally absorbed, which is why chlorophyll extracted from green plants is not properly absorbed.

Due to its health benefits (like fresh breath to an increase in blood cells), the use of liquid chlorophyll has grown over the years and it is obtained in the form of supplements called chlorophyllin which contains copper as the central metal instead of magnesium because of the reduction of the rate of absorption of magnesium chlorophyll.

Chlorophyllin is a bioavailable form of chlorophyll used as a supplement and when compared to berries, this supplement (chlorophyllin) has about 2000 times the antioxidant capacity. The supplement is taken by mixing it with fresh water known as water chlorophyll, and in some cases, the liquid chlorophyll is flavored to add to its freshness.

Chlorophyll Biosynthesis

Chlorophyll biosynthesis is an important cellular process that is required for plant photosynthesis. All the enzymes involved in chlorophyll biosynthesis in higher plants are nuclear-encoded and post-translationally imported to chloroplasts from the plastids. The biosynthesis occurs concurrently with the synthesis of other pigments such as carotenoids and pigment-binding proteins.

The overall process of chlorophyll biosynthesis can be divided into two pathways namely the light-independent pathway and the light-dependent pathway. The light-independent pathway occurs in the absence of sunlight, followed by the light-dependent pathway, which occurs as the final steps of chlorophyll biosynthesis.

Biosynthesis occurs only via the light-independent pathway in the case of bacterial chlorophyll, whereas the light-dependent pathway is the only pathway in angiosperms.

The trans-reduction of protochlorophyllide ring D to chlorophyllide is an important regulatory step in chlorophyll biosynthesis in green plants and the conversion is catalyzed by protochlorophyllide oxidoreductase, a nuclear-encoded chloroplast enzyme. The enzymes which are produced in angiosperms require light energy for catalysis, resulting in a reliance on light for chlorophyll biosynthesis.

In the case of gymnosperms, algae, and some other plants, an enzyme is produced that reduces protochlorophyllide regardless of light, allowing the organisms to produce chlorophyll in the dark.

Steps of chlorophyll biosynthesis

  1. Ligation of glutamate to tRNA
  2. Reduction of glutamyl-tRNA
  3. Transfer of amino group
  4. Condensation of two 5-aminolevulinate
  5. Formation of coproporphyrinogen
  6. Decarboxylation of coproporphyrinogen
  7. Insertion of Mg ions
  8. Formation of isocyclic ring
  9. Conversion of protochlorophyllide into chlorophyllide
  10. Formation of chlorophyll

FAQ on chlorophyll

What is chlorophyll used for?

Chlorophyll has been used for therapeutic purposes in the past. It’s currently utilized for detoxification, wound healing, constipation, colostomy odor reduction, and foul breath reduction.

What is chlorophyll in plants?

Chlorophyll is a pigment that gives plants their green color and aids in photosynthesis, which allows plants to create their own food.

What is chlorophyll good for in humans?

People use it as a health supplement, and the potential benefits of chlorophyll include improved health, increased energy, and the ability to fight illnesses.

What is chlorophyll water?

Chlorophyll water is simply water that has been supplemented with chlorophyll.

What is chlorophyll and what is its role in photosynthesis?

The role of chlorophyll in a plant is to absorb light, most commonly sunlight. The light energy is transferred to two types of energy-storing molecules. The stored energy is used by the plant to convert carbon dioxide (absorb from the air) and water into glucose, a type of sugar.

What is chlorophyll b?

This is a type of chlorophyll that is green in color and primarily absorbs blue light. By absorbing light energy, chlorophyll b aids in photosynthesis and due to its carbonyl group, it is more soluble in polar solvents than chlorophyll a.

What is chlorophyll made of?

A chlorophyll molecule is made up of a porphyrin head (four nitrogen-containing pyrrole rings arranged in a ring around a magnesium ion) and a long hydrocarbon tail.

What are chlorophyll drops?

Chlorophyllin, a semi-synthetic mixture of sodium copper salts derived from chlorophyll, is the green liquid supplement dripped into drinks.

What is chlorophyll responsible for?

Chlorophyll is responsible for the green color of many plants and algae.

What is chlorophyll liquid good for?

Liquid chlorophyll increase red blood cell count, aid in weight loss, heal damaged skin, neutralize toxins, reduce inflammation, and prevent cancer.

What is chlorophyll a?

Chlorophyll a is a type of chlorophyll that is used in oxygenic photosynthesis. It absorbs the most energy from violet-blue and orange-red light wavelengths, and it absorbs very little from green and near-green wavelengths.

What is chlorophyll supplement good for?

Chlorophyll supplement is good for stimulating the immune system, eliminating fungus in the body, detoxifying your blood, cleaning your intestines, eliminating bad odors, energizing the body, cancer prevention

What are chlorophyll drops used for?

For many years, people have used chlorophyll as a health supplement in drops. A number of medical studies have suggested that it may be beneficial for skin conditions, body odors, and the treatment of certain types of cancer.

What is chlorophyll juice?

chlorophyll juice is a liquid form of chlorophyll supplements (Chlorophyllin, a semi-synthetic mixture of sodium copper salts derived from chlorophyll).

Where is chlorophyll located?

Chlorophyll is located in chloroplasts, which are tiny structures found in plant cells. Specifically, it is located in photosystems I and II of the chloroplast.

Does chlorophyll absorb green light?

No, because it does not absorb green wavelengths of white light. Chlorophyll gives plants their green color because that particular light wavelength is reflected by the plant, it appears green.

The video briefly explains what is chlorophyll.

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