Question

In a chloroplast, enzymatic reaction to synthesize sugar takes place in

• A. the lumen of the thylakoids
• B. stroma
• C. ribosome
• D. stroma lamellae

Answer 1

The correct option is B stroma

Photosynthesis in plants is a two-step process that occurs in the chloroplast.

The first step is called the light dependent reaction which takes place in grana. Granum consists of disc-shaped structures called thylakoids, which are stacked one above the other. The grana are connected with each other by the stroma lamellae. Chlorophyll a ,chlorophyll b, xanthophyll and carotenoids are the various light absorbing pigments that are present in the thylakoid. The light energy is converted into two energy-carrying molecules (ATP and NADPH) with the involvement of enzymes in the thylakoid membrane. The process also involves the splitting of water and the release of oxygen molecules.

The products of the first reaction i.e., ATP and NADPH are used by the second reaction called the dark reaction or light independent reaction. The reaction uses carbon dioxide, water in the presence of ATP and NADPH to synthesize glucose, which serves as a food for plants. The fluid enclosed by the inner membrane of the chloroplast is called stroma and it is the site of the dark reaction. The ribosomes are present in the stroma and are involved in the synthesis of proteins.