Question

Photosynthesis is a process in which
A. CO2 is reduced to carbohydrate.
B. NADH is reduced to NAD.
C. Both A and B
D. CO2 is oxidized to carbohydrate

Answer 1

Photosynthesis is the process by which green plants obtain energy. The organisms that carry out photosynthesis are green plants, some algae and certain bacterial species. The main source of energy is sunlight for the process.

Complete answer:
During photosynthesis plants obtain energy by capturing sunlight along with CO2 and water absorbed from atmosphere and soil respectively. The end product of the process is carbohydrates stored as the reserve food material. And the by-product of the reaction is oxygen which gets released into the atmosphere. During the process of photosynthesis CO2 gets reduced to carbohydrates.
Considering the other given options:
B. During the process, NAD is reduced to NADH and these molecules function as an energy carrier. Later during the cycle NADH is oxidized back into NAD. Thus it is not the right option.
C. Since option B is not applicable to photosynthesis even though A is, it is not the right option.
D. During photosynthesis CO2 is not oxidized, but reduced to form carbohydrates, since carbohydrates are a reduction product. Thus it is not the right option.

So, the correct answer is “Option A”. That is, photosynthesis is a process in which CO2 is reduced to carbohydrates.

Note:
The process of photosynthesis takes place within the cell organelles known as chloroplasts. The pigment chlorophyll is present within the chloroplasts which is essential for the process to take place. This pigment gives green colour to the leaves. It is also a major source of replenishing oxygen levels in the atmosphere and markedly different from cellular respiration.