Chapter 7, Problem 1SQ

Summary Introduction

To determine: The structure of the chloroplast where light reactions take place and also the site where the Calvin cycle take place.

Introduction:

The chloroplast is plastid organelle present in green leaves and algae. This is the site for photosynthesis. Photosynthesis is a process in which sunlight is used to prepare the nutrients which is stored in the form of starch. The choloplast contains the chlorophyll, thlakoid, grana and stroma.

Answer to Problem 1SQ

Correct answer: The light reactions take place in the structures of the chloroplast called the thylakoid, while the calvin cycle takes place in the stroma

Explanation of Solution

The chloroplast is plastid organelles which involves in the photosynthesis. The chloroplast is double membrane bound organelle which contains the chlorophyll pigments, stroma, grana and thylakoid. The thylakoid is present in the inner membrane of chloroplast which absorbs the light energy and provides green color to chloroplast. The thylakoid membrane also contains the two photosystem unit or complex (PSI and PSII) which involves in the light reaction.

The stroma is the fluid or aqueous layer which is present in the inner membrane of the chloroplast. The stroma consist the stack of grana molecules and various metabolic enzymes and proteins are also present in the stroma which involves in Calvin cycle. Thus, the dark reaction or Calvin cycle takes place inside the stroma of the chloroplast where ATP and NADH are synthesized.

Conclusion

The thylakoid membrane of chloroplast involves in the light reaction while the stroma of the chloroplast involves in the Calvin cycle.