The Stages of Photosynthesis

What are the stages of Photosynthesis?

The process of photosynthesis is broken down into two major stages: light-dependent reactions and light-independent reactions.

Photosynthesis starts with the light reactions which happen during the day as this step requires a source of light energy since the process cannot take place without it. The light-dependent reactions take place in the thylakoid membrane of chloroplasts. 

The chlorophyll absorbs the light energy which is converted into chemical energy in the form of two compounds: ATP (Adenosine tri-phosphate) and NADPH (Nicotinamide adenine dinucleotide phosphate). ATP is an energy storage molecule and NADPH is a reduced electron carrier. 

Water molecules are also converted to oxygen gas. Photosynthesis produces oxygen as a waste product. It is released into the atmosphere through the stomata.

The light-independent stage takes place in the stroma. It is found between the thylakoid and the chloroplast membranes. This stage removes carbon dioxide and turns it into sugars. This stage does not require light as it utilizes energy obtained from the ATP and NADPH molecules. The energy is used to create carbohydrate molecules such as glucose. These sugars are formed from carbon dioxide which plants retrieve from the atmosphere via the stomata.

 Glucose is referred to as the food of plants. It can be used to store energy in the form of large carbohydrate molecules known as polysaccharides. Glucose is a simple sugar molecule which comes together with other glucose molecules to produce polysaccharides such as starch. The starch produced is converted to sucrose as it is easier to transport around the plant and is exported from the leaf to other parts of the plant. It is used to produce other molecules required by the plant.

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Do you know the other name for the light independent stage of photosynthesis?

What role does light play in these reactions?

 

References

  published, D. D. (2021, November 24). What is photosynthesis? Livescience.com. https://www.livescience.com/51720-photosynthesis.html#section-types-of-photosynthetic-processes

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