Question

Which of the given structures of cyanobacteria has functional resemblance with the chloroplast?
A) Lamellasome
B) Plasma membrane
C) Ribosome
D) Chromatophore

Answer 1

Hint: Cyanobacteria are the photosynthetic bacteria which lives in aquatic habitat. It is also known as blue-green algae. Unlike algae they prokaryotes. Cyanobacteria are the most primitive organisms from which the modern-day plants have evolved. The chloroplasts are the photosynthetic centres which contain chlorophyll that have evolved from the photosynthetic pigment present in the cyanobacteria.

Complete answer:
To answer this question, we must know about the structure of cyanobacteria.
- They have a definite cell wall made up of peptidoglycan. The cell wall of eukaryotic plants is made up of cellulose and chitin.
- They have a definite plasma membrane, outer membrane and internal thylakoid membrane. The plasma membrane protects the cell from the external environment.
- All the definite membranous organelles like Endoplasmic reticulum, golgi, chloroplast are absent.
- Ribosomes are the protein synthesis centres of the cell. The cyanobacteria have 70s ribosomes whereas eukaryotic plants have 80s ribosomes.
- The cytoplasm of BGA have specialised compartments called the chromatophores. It contains photosynthetic pigments like chlorophyll a, carotenes, xanthophylls. These are similar to chloroplast present in the eukaryotes which perform the similar function of photosynthesis.
- Definite nucleus is absent in cyanobacteria.

Thus the correct answer is option ‘D’.

Note: Chloroplasts are the photosynthetic centres present in the plant cell. They contain a green pigment called chlorophyll which absorbs sunlight for carrying out photosynthesis. The cyanobacteria also have fucoxanthin and phycoerythrin which are blue and red coloured pigment respectively.