Bihar Police Constable Model Paper 4

Concept:

• Cell organelles are surrounded by an envelope or covering called a membrane.
• Based on the presence or absence of these membranes cell organelles can be grouped into different categories.
• No membrane - Ribosomes, Nucleolus
• Single membrane - Nucleus, Lysosomes, Golgi bodies, Endoplasmic reticulum, etc
• Multiple membranes - Mitochondria and chloroplast are double membrane-bound.

Explanation:

Chloroplast:

• The chloroplast is a double membrane-bound cell organelle.
• Out of the two membranes, the inner membrane is relatively less permeable. (the outer membrane contains porins).
• The space limited by the inner membrane is called the stroma.
• Chloroplasts contain chlorophyll and carotenoid pigments which are responsible for trapping of light energy essential for photosynthesis.
• The majority of chloroplasts are found in the mesophyll cells of the leaves.