Q1TYU - Campbell Biology

Question

The light reactions of photosynthesis supply the Calvin cycle with

1. light energy.
2. CO₂ and ATP.
3. H₂O and NADPH.
4. ATP and NADPH.

Step-by-Step Solution

Answer

1. The option “light energy” is false.
2. The option “CO₂ and ATP” is false.
3. The option “H₂O and NADPH” is false.
4. The option “ATP and NADPH” is true.

Step 1: Photosynthesis

The process by which photosynthetic organisms convert the sun’s light energy to chemical energy is referred to as photosynthesis. Light reaction and Calvin cycle are two phases in which photosynthesis occurs.

Step 2: Explanation of option (A)

Light energy is the solar radiation of the sun. 

 

Thus, light energy is provided by the sun and not the light reaction of photosynthesis.

Therefore, the given option is false.

 

Step 3: Explanation of option (B)

ATP is produced in the light reaction of photosynthesis, whereas CO₂ is obtained from air and is fixed and converted into carbohydrates during the Calvin cycle of photosynthesis. 

 

Thus, light reaction provides ATP to the Calvin cycle but not CO_2.

Therefore, the given option is false.

Step 4: Explanation of option (C)

 

H₂O splits to produce oxygen molecules during photosynthesis, whereas NADPH is produced during light reactions. 

 

Thus, light reaction provides NADPH but not water to the Calvin cycle.

Therefore, the given option is false.

 

Step 5: Explanation of option (D)

During the light reaction of photosynthesis, chlorophyll present in chloroplasts absorbs solar radiation and converts it into chemical energy in ATP and NADPH. 

 

Thus, light reaction provides both ATP and NADPH to the Calvin cycle.

Therefore, the given option is true.