Question

How would you explain how the light-independent reaction of photosynthesis relies on the light-dependent reactions?

Answer 1

Hint: Photosynthesis is a technique through which plants prepare their food. The complete process occurs in two sequential stages and these stages are so related to each other that one stage supports the other either by supplying fuel or as a carrier of the same.

Complete answer:
To complete the process of photosynthesis light-dependent and light-independent reactions are two successive reactions. In the photosynthesis process, the energy from the sun or sunlight is absorbed by the chlorophyll and converted into chemical energy during the light-dependent reactions of photosynthesis. The energy obtained from the sun is converted in the form of electron carrier molecules like NADPH (nicotinamide adenine dinucleotide phosphate) and ATP (adenosine triphosphate). The chemical energy produced during light-dependent reactions is used to construct carbohydrate molecules from carbon dioxide during the light-independent reactions ( the Calvin cycle). So, from the above explanation, it is clear that both the types of reactions are essential and the occurrence of light-independent reactions is impossible without or in the absence of light-dependent reactions.
-From the name, it is clear that light-dependent reactions need sunlight to occur and it produces electron carrier molecule NADPH and the energy currency molecule ATP as the end product.
-The light-dependent reactions happen inside the chloroplast within the thylakoid membranes which is found in the granum or stack of thylakoids.
-From the name again it is clear that light-independent reactions do not need sunlight to occur because it gets its energy supply from the end products of light-dependent reactions i.e., ATP and NADPH.
-During light-independent reactions carbohydrates are derived from the breakdown of carbon dioxide molecules.
-Because of the cyclical nature of the process, the light-independent reactions are sometimes called the Calvin cycle.
-The Calvin cycle can take place day or night, they only require the end products from light-dependent reactions to function properly.
-After transferring the energy during light-independent reactions, the energy carrier molecules (NADPH) return back to the light-dependent reactions to get more and more energized electrons for the reactions.
-The light also activates several enzymes of the light-independent reactions.

Note:
-Photosystems are part of photosynthesis and are biochemical systems that are active in chloroplasts.
-In Photosystems I and II, the light energy is harnessed and both the photosystems are present in the thylakoid membranes of chloroplasts.
-The end product of light-dependent reactions is ATP and NADPH. They return to the first stage after transferring energy in the second stage i.e., light-independent reactions.