Chapter 8, Problem 1TYU

The light reactions of photosynthesis supply the Calvin cycle with

1. A.   light energy.
2. B.    CO₂ and ATP.
3. C.    O₂ and NADPH.
4. D.   ATP and NADPH.

Summary Introduction

Introduction:

The reaction directly dependent on light are called light reaction and occurs in the grana and stromal thylakoid of chloroplast. The light independent reaction is called the dark reaction. It occurs in the stroma of chloroplast.

Answer to Problem 1TYU

Correct answer:

Light reaction uses the sunlight to split water and pass electron through the photosystems to make energy for the production of sugar by the dark reaction. Therefore, option (D) is correct.

Explanation of Solution

Reason for the correct statement:

Thylakoid present in the chloroplast has two types of photosystems. These help in the conversion of solar energy into the usable chemical energy. Photosystem I produces ATP only and photosystem II produces ATP and NADPH. These chemical forms of energy are used in Calvin cycle to make sugar.

Option (D) is given as “ATP and NADPH”.

“The light reaction of photosynthesis supply the Calvin cycle with ATP and NADPH”, it is the right answer.

Hence, option (D) is correct.

Reasons for the incorrect statements:

Option (A) is given as “light energy”.

The light reaction requires light energy to produce, ATP and NADPH molecules. So, it is a wrong answer.

Option (B) is given as “ ${\text{CO}}_{\text{2}}$ and ATP”.

Carbon di oxide is supplied to the calvin cycle but not the ATP. So, it is a wrong answer.

Option (C) is given as “ ${\text{O}}_{\text{2}}$ and NADPH”.

NADPH and oxygen are given by the light reaction but oxygen is not supplied to the Calvin cycle, it has no use in it. So, it is a wrong answer.

Hence, options (A) (B) and (C) are incorrect.

Conclusion

The light reaction provides the dark reaction, Calvin cycle, with ATP and NADPH for making organic products.