Question

Photosynthetic pigments are located in the chloroplast in
(a) Intra Thylakoid space
(b) Thylakoid membranes
(c) Intermembrane space
(d) Inner membrane of envelope

Answer 1

Hint: The light reaction occurs in the grana part of the chloroplast while the dark reaction takes place in the stroma part of the chloroplast. These are massive membrane systems, which run parallel to each other and are found in the stroma.

Complete answer:
The photosynthetic pigments are located in the thylakoid membrane of the chloroplast. In higher plants, chloroplast possesses two types of thylakoid- large and small. The large thylakoids are known as stroma thylakoids, extending from one end to the other end of the chloroplast. The small thylakoid is disc- shaped which is closely packed at places to form grana thylakoids. The grana thylakoids fuse with large stroma thylakoids in a region called ‘granum.’
- The stroma contains photosynthetic pigments and protein-rich fluids.
- The chloroplast is a double membrane- bound body that contains the green photosynthetic pigment chlorophyll.
- In green cells of higher plants, the number of chloroplasts ranges from 20-100.
- Thylakoids or lamellae lie freely in the cytoplasm but without any specific envelope.
- In chloroplasts porphyrin heads of chlorophyll molecules are associated with protein and their phytol tail is associated with the lipid layer.
- The carotenoids (carotenes and xanthophylls) are the pigments that are sandwiched between the phytol tails and the phospholipid molecules.
- The presence of nucleic acid makes the chloroplast semi autonomous and self- replicating organelle.
- The molecular model of chloroplast was proposed by Frey and Wyssling in the year 1953.
So, the correct answer is, ‘Thylakoid membranes.’

Note:
- Chloroplasts are absent in blue- green algae and non- photosynthetic bacteria and fungi.
- It has been reported that certain coupling factors as ATP- ase and photosynthetic pigments (photosystem- 1 and photosystem- 2) are located in the thylakoid membrane.