A Guide to Photosynthesis: Process, Types, and Importance

KOMPAS.com – Photosynthesis is the process commonly used by plants in converting sunlight into food or energy.

The process converts carbon dioxide and water into food and oxygen. Photosynthesis is also the reason why the earth is covered in an oxygen-rich atmosphere.

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Reporting from the National Geographic page, photosynthesis is a process carried out by plants, algae, and several types of bacteria.

They capture energy from sunlight to produce oxygen and chemical energy which is stored in glucose (sugar).

Herbivores then get this energy by eating plants, and carnivores get it by eating herbivores.

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Photosynthesis process

During the process of photosynthesis, plants take in carbon dioxide and water from the air and soil.

In plant cells, water is then oxidized or loses electrons, whereas carbon dioxide is reduced, meaning it gains electrons.

This process then turns water into oxygen and carbon dioxide into glucose. Plants then release oxygen back into the air, and store energy in glucose molecules.

In addition, in plant cells there are small organelles called chloroplasts, which are capable of storing energy from sunlight.

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And in the thylakoid membrane of the chloroplast there is a light-absorbing pigment called chlorophyll, which is also responsible for giving plants their green color.

Chlorophyll absorbs energy from light waves, which is converted into chemical energy in the form of ATP and NADPH molecules.

During this stage, energy from ATP and NADPH molecules is used to assemble carbohydrate molecules, such as glucose, from carbon dioxide.

During photosynthesis, chlorophyll absorbs energy from blue and red light waves, and reflects green light waves, making plants appear green.

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Types of photosynthesis

Reporting from the Live Science page, there are three main types of photosynthesis which all produce sugar from CO2 using the Calvin cycle.

However, each of these types, through slightly different paths.

1. Photosynthesis C3

Most plants use C3 photosynthesis. C3 crops include cereals (wheat and rice), cotton, potatoes and soybeans.

This process of photosynthesis is named for the three-carbon compound 3-PGA that it uses up during the Calvin cycle.

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2. Photosynthesis C4

Plants such as corn and sugarcane use C4 photosynthesis. This process uses a four-carbon compound (called oxaloacetate) which is converted to malate.

Malate is then transported into the bundle sheath where it decomposes and releases CO2, which is then fixed by rubisco and made into sugars in the Calvin cycle (as with C3 photosynthesis).

C4 plants are better adapted to hot, dry environments and can continue to fix carbon even when their stomata are closed.

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3. CAM photosynthesis

Crassulacean acid metabolism (CAM) is found in plants adapted to very hot and dry environments, such as cacti and pineapples.

When stomata open to absorb carbon dioxide, they run the risk of losing water to the outside environment. Because of this, plants in very arid and hot environments have adapted.

One form of adaptation is CAM, in which plants open their stomata at night (when the temperature is lower and the risk of water loss is less).

Carbon dioxide enters the plant through the stomata and is fixed to oxaloacetate and converted to malic or other organic acids (as in the C4 pathway).

Carbon dioxide is then available for light-dependent reactions during the day, and the stomata close, reducing the risk of water loss.

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2023-07-19 00:45:00
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