Chlorophyll

Chlorophyll is a green pigment found in cyanobacteria and the chloroplasts of algae and plants. It makes plants and algae look green. The name comes from Greek words meaning "pale green" and "leaf".

Chlorophyll helps plants take in energy from light. It is very important for a process called photosynthesis, where plants make their own food using sunlight. Chlorophyll helps make oxygen during this process.

Chlorophyll works best with blue and red light. It does not work well with green light, which is why plants look green. Two main types, chlorophyll a and b, work together in tiny parts of plant cells to do this important job.

History

Chlorophyll was first found and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817. Later, scientists learned that magnesium is part of chlorophyll. This was the first time this element was found in living things.

More work on chlorophyll’s structure was done by Richard Willstätter from 1905 to 1915. Then, Hans Fischer learned the basic shape of chlorophyll a in 1940. By 1960, most of how the parts of chlorophyll a fit together was known, and Robert Burns Woodward made the whole molecule in a lab. In 1967, Ian Fleming finished learning the last pieces. In 1990, Woodward and others updated how to make it. In 2010, scientists found that chlorophyll f exists in cyanobacteria and other tiny organisms that build stromatolites. They learned its formula is C₅₅H₇₀O₆N₄Mg.

Photosynthesis

Chlorophyll is very important for photosynthesis. This is the way plants get energy from light.

Chlorophyll is found inside special parts of plant cells called photosystems. It helps in three main ways: it catches light, sends the light energy to a special spot, and helps make energy for the plant and oxygen for us to breathe. This process uses tiny parts of the plant to make energy and oxygen from water and sunlight.

Chemical structure

Several types of chlorophyll exist, and they all come from a basic green ring structure. Most chlorophyll is similar to a group called porphyrins, which are found in things like hemoglobin. Instead of iron, chlorophyll usually holds magnesium. Plants often have a long chain attached to this structure. The most common type in land plants is chlorophyll a. Chlorophyll a differs slightly from chlorophyll b, which helps plants absorb more light.

The different forms of chlorophyll include:

• Structures of chlorophylls

• chlorophyll a

• chlorophyll b

• chlorophyll c₁

• chlorophyll c₂

• chlorophyll d

• chlorophyll f

Chlorophyll e was found in algae in 1966 but has not been fully described. There are also many small changes to chlorophyll structures found in nature. For example, a tiny blue-green organism called Prochlorococcus uses a special form of chlorophyll a and b.

Measurement of chlorophyll content

Scientists can take chlorophyll from plants and put it into special liquids to see how much is in a leaf. They can tell apart two types of chlorophyll, called chlorophyll a and chlorophyll b.

They study how chlorophyll takes in light using different liquids. For example, in one liquid, chlorophyll a takes in light best at some colors, and chlorophyll b takes it in best at other colors. There are also ways to measure chlorophyll by seeing how it glows when light shines on it. These ways help scientists know how much chlorophyll is in a leaf without hurting the plant. Tools like Dualex and SPAD can quickly measure chlorophyll, just like lab tests do.

Biosynthesis

In some plants, chlorophyll is made from special building blocks. It follows a path shared with other important plant parts. A special enzyme helps finish making chlorophyll a.

Plants that do not get enough light can stay pale. But some simpler plants and green algae can grow green without light because they have an extra helper enzyme.

Chlorophyll attaches to special proteins in plants. Plants carefully control how much chlorophyll they make to stay safe.

Senescence and the chlorophyll cycle

When plants get older, they go through a process called senescence. During this time, chlorophyll—the green pigment that helps plants make food—breaks down. Special enzymes help change chlorophyll into other substances. This lets plants reuse some parts of chlorophyll.

Eventually, chlorophyll turns into colorless compounds found in ripening fruits. These changes help the plant get ready for the end of its life cycle.

Distribution

Chlorophyll maps from 2002 to 2024, from NASA, show how much chlorophyll is in the ocean each month. Blue areas have little chlorophyll, meaning few tiny ocean plants called phytoplankton. Yellow areas have lots of chlorophyll, meaning many phytoplankton are growing.

These maps come from a tool on NASA's Aqua satellite. The darkest gray shows land, and light gray shows where the satellite couldn't get data. The most chlorophyll is found in cold polar waters or where ocean currents bring cold, nutrient-rich water to the surface. These nutrients help the phytoplankton grow when sunlight returns in spring and summer.

Uses

Chlorophyll is used as a natural green color in foods and drinks. Chefs add it to pasta, drinks, and spirits to make them look green. For example, a drink called absinthe gets its green color from herbs used to make it, which contain chlorophyll.

In the past, some companies used chlorophyll in products like toothpaste and soap, saying it could help remove bad smells. But later, people found out these claims were not true, so they stopped using it. Recently, some people on social media influencers have talked about drinking "chlorophyll water," but these health claims are not proven.