How Does Chlorophyll Work And Why Is It So Important?

Chlorophyll can certainly be considered one of the most important pigments on Earth and is present in all green plants.

Not only does chlorophyll assist plants in the process of photosynthesis, it also helps sustain plant life and produce oxygen for the entire planet.

How Does Chlorophyll Work And Why Is It So Important?

Chlorophyll is an incredibly unique pigment that allows plants to function at all, it is the key to a plants survival and a huge part of the growth process, with its role in photosynthesis working to sustain plant life on our planet entirely.

The exact structure, formation and inner workings of Chlorophyll are a bit more complex and involve multiple different components that allow it to function how it does, therefore to make this clearer, we have taken a deep dive into chlorophyll and how exactly it works.

History

Photosynthesis was first discovered in 1780 by famous English chemist Joseph Priestly who conducted several experiments and tests on various plants to analyze how they produce oxygen.

Priestly used a mint plant, placed it into an upturned jar in a vessel of water for several days and was soon amazed by noticing that the plant had been producing oxygen.

A few decades later in 1817, chlorophyll became isolated and uncovered by Joseph Bienaime Caventou and Pierre Joseph Pelletier who first coined the name.

Chlorophyll was further analyzed until in the early 20th century, German scientist Richard Willstatter discovered that the pigment seemed to appear in special structures called chloroplast.

Chlorophyll A and chlorophyll B were also purified and divided by definition by Willstatter for which he was awarded with a Nobel Peace Prize for.

By the 1930’s chlorophyll A and B were chromatographically separated and in the 1960’s, US scientist Robert Burns Woodward had been researching and discovered the structure of a chlorophyll molecule, earning him a Nobel Prize in chemistry.

Since the late 1960’s there have been some more studies and updated synthesis on chlorophyll, however a lot of its properties and biological makeup are well known to us at this point.

Definition

Chlorophyll as we know it today is a molecule produced by plants, algae and cyanobacteria and is known as a pigment or a molecule that reflects some wavelengths of light.

There are two specific forms of Chlorophyll in plants: Chlorophyll A and Chlorophyll B.

While both absorb wavelengths of light, the A variant absorbs dark blue wavelengths and dark red ones while chlorophyll B works to absorb light blue and red or orange waves.

All plants possess both of these which is necessary to absorb both blue and red light waves.

There are also a few other forms of chlorophyll that mostly act as accessory pigments that are far less widely distributed than the A and B forms.

Chlorophyll C

This variant produces a blue-green color that absorbs light in the 447-520nm wavelength regions.

The chlorophyll pigments present in the C form are further divided into chlorophyll c1, c2 and c3.

Depending on the actual organism, chlorophyll C can co-occur with other pigments and has also been shown to be much different in structure to other variants.

For example, chlorophyll C has been shown to be Mg-phytoporphyrins and at the C-17 ring, the structure itself is made up of propanoic acid.

Chlorophyll D

A much rarer variant found mostly in some species of red algae and cyanobacteria.

It is a very important pigment in free living cyanobacteria that live in light environments acquiring less visible light and enhanced infrared radiation.

In contrast to chlorophyll A, chlorophyll D has a formyl group which exchanges the space usually used for a C3-vinyl group which is located on the chemical structure of ChI a.

Chlorophyll E

Another rare variant often found in some golden algae, it is primarily within Tribonema bombycinum and Vaucheria hamata.

Chlorophyll F

When it comes to both chlorophylls E and F, they were discovered very recently as late as 2010, so their exact structure and function within the photosynthesis process is as of yet unclear, however they have been shown to be vital in the process for the species they exist within.

From what research has been successfully laid out however, chlorophyll F has been found to be most prominent in wetlands cyanobacteria.

The primary reason discovering chlorophyll F was such a breakthrough was because it was once assumed that oxygen producing microorganisms were not capable of being able to use infrared light as a source of energy.

This changed with the F variant which was found to be capable of absorbing high amounts of near infrared-lights when compared to other forms of chlorophyll.

For this reason, it majorly helps the organism harvest from an alternate light wavelength.

Structure

The molecule formula for Chlorophyll is C55H72MgN4O5.

The molecule itself consists of a central metal core surrounded by a nitrogen containing structure, resulting in a porphyrin ring.

All different chlorophyll molecules are characterized by the presence of four pyrrole-like rings which are called tetrapyrroles, along with an additional fifth ring.

Chlorophyll is also classed as a chlorine which is closely related to porphyrins such as hemoglobin.

Among all the different variants, the structure of chlorophyll A is the most studied which is found in all living organisms capable of photosynthesis.

It possesses the same basic structure as other chlorophyll with a chlorine ring where four nitrogen atoms surround the magnesium ion with the only primary difference being that it has a side chain attached to this ring.

How Does A Chlorophyll Function?

How Does A Chlorophyll Function?

There are a few processes that take place in both chlorophyll A and B that allow them to work and absorb light the way they do.

Both types of chlorophyll are located in the thylakoid membranes of chloroplasts which are the organelles where photosynthesis takes place.

Embedded within these membranes are a wide variety of proteins that surround the chlorophyll which work together to transfer energy from the light, and then into the bonds of ATP.

The proteins which transfer the energy from light rays and channel it into the synthesis of sugars are known as photosystems and are the main component that allows photosynthesis to work at all.

These organisms take in carbon dioxide, water and sunlight to then produce glucose which they can then use in the process of cellular respiration to create ATP.

How Is Light Captured By Chlorophyll?

In terms of the actual inner working of chlorophyll, while chlorophyll absorbs most colors it does not absorb green light which is reflected and is what gives the plants their green color.

Instead, the chlorophyll absorbs red and blue lights which activates some electrons within the inner ring of the pigment.

These lights that are absorbed are then used to energize electrons which break free from a chlorophyll atom to enter an electron transfer chain, which is why chlorophyll is sometimes referred to as an electron donor.

The process then continues with an electron being passed down the electron transport chain before finally reaching the electron acceptor where the electron is then transferred to an organic molecule known as plastoquinone.

When electrons pass through the chain, it causes them to change from a higher to lower energy with some of the leftover energy being used to pump hydrogen protons from the stroma.

To finish off the process, the electron will then join a ChI where it will be re-energised to make up for what it lost while traveling through the electron chain.

Once fuelled back up, it must then travel through a much shorter transportation chain until it finally reaches the NADP+ reductase.

Here, the electron transfers the electron to NADP+ and is then moved to the Calvin Cycle.

What Is The Calvin Cycle?

The Calvin Cycle is a vital stage of photosynthesis and so is worth knowing about as part of the process of absorbing light and extracting oxygen.

There are four main stages to the Calvin Cycle:

  • Carbon fixation – This is where the plant will bring in Co2 and attach it to another carbon molecule, using rubisco which is an enzyme that can help the reactions move a bit faster. This step is extremely important, and is the reason why rubisco is the most common protein on Earth and in chloroplast. The rubisco will then attach the carbon in Co2 to a five carbon molecule called ribulose to create a six carbon molecule.
  • Reduction – The ATP and the NADPH from the light reaction then make an appearance and transform the two or three carbon molecules into two small sugar molecules.
  • Formation of carbohydrates – Some of these sugar molecules will then leave the cycle in order to be converted into bigger sugars such as glucose.
  • Regeneration phase – Finally, some sugar molecules will go on to create glucose while others are used to recharge the RuBP acceptor.

The Calvin Cycle is incredibly important because its primary function is to produce organic products that plants need by using the products from the light reactions of photosynthesis.

These organic products include glucose, the sugar made using carbon dioxide, water and protein.

Chloroplast

Chloroplasts are worth mentioning because they are essentially the cousin to chlorophylls.

Chlorophylls are found in both eukaryotes and prokaryotes, however chloroplasts are only found in eukaryotic plants and algae.

Chloroplasts are found in the cells of the mesophyll layer where photosynthesis takes place, they are surrounded by a double membrane separating the inner parts of the organelle from the intracellular environment.

They are a vital component of photosynthesis that helps the entire process to function as it should.

A chloroplast is made up of an outer membrane, followed by an intermembrane space with Thylakoid and Granum then making up the center.

Grana are made up of stacks of disc shaped structures known as thylakoids or lamellae.

The grana from the chloroplast consists of chlorophyll pigments which work as the primary functional units.

Stroma on the other hand is the homogenous matrix which actually contains grana and is similar to the cytoplasm in cells in which all the organelles are embedded.

In addition to this, stroma also contains various enzymes such as DNA, ribosomes and several other substances.

The way stroma functions is by actually connecting the built up stacks of thylakoid sacs or grans together.

Chloroplasts are also vital in the process of converting light energy into sugar and other organic molecules that plants and algae use as food.

This is the most important and primary function of chloroplasts, to synthesize food by the process of photosynthesis and also using CO2 obtained from the air to generate carbon and sugar during the Calvin Cycle or dark reaction of photosynthesis.

The primary difference between chloroplast and chlorophyll is that the former is the organelles involved in photosynthesis while the latter is the pigment involved in the process.

Chlorophylls are also not composed of their own organelle DNA whereas chloroplasts are which is called cpDNA.

Chlorophyll is also found in all plants, algae and cyanobacteria while chloroplast is within all plants and algae but no cyanobacteria.

In terms of where they are actually located, while chlorophyll is often found in the thylakoid membrane of chloroplasts, chloroplasts themselves are often found in the leaves of plants.

Additionally, while there are many variants of chlorophyll such as A, B and C, chloroplasts just have two variants being in algae and plants respectively.

How Does Photosynthesis Work?

Chlorophyll is the primary molecule that reflects green light and absorbs other colors which is then converted into energy, however while it helps facilitate photosynthesis, there are a few key stages to the process itself which can be useful to know.

Oxygen is produced in the first part of the light cycle of photosynthesis which is used for cellular respiration, but will also release any excess oxygen into the air.

To do this, the plant will split water molecules in order to create electrons, hydrogen ions and diatomic oxygen.

The electrons then supply the electron transport chain that drives ATP production. The oxygen is then released into the air.

Plants also require a good amount of energy to grow, develop and bloom and photosynthesis solves this issue for them perfectly.

It allows them to prepare their own food, but also convert light energy into chemical energy which can keep plants energized once absorbed.

This process of photosynthesis that is facilitated by chlorophyll is incredibly important and beneficial for plants primarily because it allows them to be able to produce their own food by producing glucose.

It is not just necessary for the wellbeing of plants, but also to keep things functioning within the biosphere.

Photosynthetic organisms form the base of Earth’s food webs and additionally, almost all oxygen that we breathe in comes from the process of photosynthesis, making it vital for both our and plants survival.

Benefits Of Photosynthesis

Benefits Of Photosynthesis

The process of photosynthesis itself is well known and has been thoroughly researched in recent decades, as well as the role of chlorophyll in the entire process.

However there are a huge plethora of benefits caused by photosynthesis that can be slightly lesser known.

For one, there are a huge amount of medical benefits that we can research from the entire process.

Skin cancer and aging are examples of some of the numerous detrimental light effects that can occur on both animals and humans.

However, because plants and other photosynthetic living organisms have been handling light for a long time, as a result many have developed mechanisms for limiting light damage.

Researching these mechanisms that plants use to protect themselves from the dangerous effect of sunlight has actually been seen in recent years to be a great source to study potential ways to adapt such strategies to humans.

Another way it can actually benefit humans is in the process of energy production.

Extensive photosynthesis research can and has been undertaken to improve energy production making it both more efficient and much cleaner for the environment.

Even though the actual process of photosynthesis can be somewhat wasteful, the actual first step of converting sunlight into a form of energy is incredibly useful and has already been adapted to utilize and build solar energy devices.

Photosynthesis is also vital to our actual bodily requirements.

Majority of our food requirements are actually met by plants, this is both from the plants themselves and from herbivores eating them such as cows.

Through photosynthesis, plants are able to manufacture foodstuffs which makes food readily available, even though we might not even realize it.

If it wasn’t already positive enough, the process of photosynthesis plays a huge part in helping the environment and cutting down harmful gasses.

Photosynthesis works to remove carbon dioxide gas from the environment and in its place, release oxygen for us to breathe in.

Once the oxygen is dispersed, it absorbs the ultraviolet radiation and forms the beneficial ozone layer.

Downsides Of Photosynthesis

There are extremely little downsides to the process of photosynthesis, the natural process helps plants prepare food, stay energized and releases oxygen which we need to survive.

There are some drawbacks however, mainly its limited area and time.

Photosynthesis cannot be done in a shaded or darker area since it relies on the sun meaning for some spaces the process is unable to occur.

This also means it cannot be done at night with it being exclusive to the daytime.

Added to this, photosynthesis is also very sensitive to cold conditions as well as heat.

While the process takes far longer in chiller conditions, too much or too little sunlight can also reduce the rate of photosynthesis which can sometimes make it hard to judge how much is necessary for an individual plant.

Oxygenic photosynthesis, the kind produced by green plants, also depends on a slow and quite inefficient enzyme known as rubisco.

While there is more rubisco than any other protein, it is extremely slow with less than 10 reactions per second while other enzymes will catalyze thousands of reactions each second.

It is also seen as quite inefficient because it is capable of catalyzing the reverse reaction which causes a lot of material and energy to go to waste.

No living organism has been able to evolve a better enzyme than rubisco and the fact it has not improved over the course of 3 billion years shows it’s struggling in its function.

This being said, these drawbacks are very minimal and do not overshadow the enormously important role photosynthesis plays in keeping plants, animals, humans and the Earth healthy.

What Organisms Can Photosynthesise?

It is well known that plants and algae can photosynthesise, however there are an extremely small number of parasitic and mycoheterotrophic species that contain chlorophyll and produce their own food in a similar way.

Cyanobacteria and certain sulfur bacteria are also classed as photosynthetic prokaryotes, which too take part in photosynthesis.

In terms of animals, no animals have been found to be independently capable of photosynthesis.

The only animal that has even come close to resembling some form of photosynthesis is the emerald green sea slug which has the ability to temporarily incorporate algae chloroplasts in their body for the sake of food production.

Despite this, animals that eat plants or other animals are called heterotrophs and while they are not capable of photosynthesis themselves, they are certainly a part of the process that betters the ecosystem.

Because food webs are present in every type of ecosystem, from terrestrial to marine, all species begin with photosynthesis and essentially rely on the process for the food they eat to be healthy and fresh and provide the necessary nutrients, chlorophyll in this sense can be regarded as the foundation for all life on Earth.

Summary

Overall, chlorophyll can be considered not just the most important component of photosynthesis, but also one of the most important parts of allowing our ecosystem to work efficiently in the way that it does.

Photosynthesis is at the core of all living things, it keeps plants healthy and energized while also allowing them to exert oxygen for us to breathe and maintaining a continuous food source that has created entire food webs between essentially all living species on the planet, whether this be underwater or mammals living on land.

Without photosynthesis, very soon there would end up being little to no food or actual organic matter on Earth with most organisms disappearing and the Earth’s atmosphere becoming entirely devoid of any gaseous oxygen.

Luckily these disastrous scenarios are prevented thanks to the chlorophylls which are present within all plants, algae and cyanobacteria and function to absorb light and convert it into energy, keeping the plants and in turn the Earth healthy.

Jennifer Dawkins

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