Chapter 8, Problem 1U

The light-dependent reactions of photosynthesis are responsible for the production of

a. glucose.

b. CO₂.

c. ATP and NADPH.

d. H₂O.

Summary Introduction

Introduction:

Photosynthesis is a metabolic process that happens in photoautotrophs like plants. It uses water and carbon dioxide to make glucose and release oxygen. It happens in the chloroplast and is divided into light and dark reaction.

Answer to Problem 1U

Correct answer:

Light reaction converts solar energy into chemical energy (ATP and NADPH) for use in dark reaction. Therefore, option c. is correct.

Explanation of Solution

Reason for the correct statement:

Light reaction is directly dependent on the sunlight. It absorbs the solar energy using pigments (chlorophyll) and converts it into ATP and NADPH molecules (chemical energy) by the process of photophosphorylation.

Option c. is given as “ATP and NADPH”.

As “the light-dependent reactions of photosynthesis are responsible for the production of ATP and NADPH”, is the right answer.

Hence, option c. is correct.

Reasons for the incorrect statements:

Option a. is given as “glucose”.

The dark reaction of photosynthesis produces glusoce not light reaction. So, it is a wrong answer.

Option b. is given as “ ${\text{CO}}_{\text{2}}$”.

Carbon dioxide is a by-product of photosynthesis and is released during the dark reaction not light reaction. So, it is a wrong answer.

Option d. is given as “ ${\text{H}}_{\text{2}}\text{O}$”.

Water is used during the light reaction of photosynthesis and not produced. So, it is a wrong answer.

Hence, options a., b. and d. are incorrect.

Conclusion

ATP and NADPH molecules are produced during the light reaction of photosynthesis.