Question

Explain types of chloroplast.

Answer 1

Hint: Chloroplasts are specialized organelles, present in algae and plants, which contain chlorophyll and carotenoid pigments. Chlorophyll, along with other pigments, traps the sunlight energy which is required by the plants to perform photosynthesis.

Complete answer:
In green plants, chloroplasts are mostly present in the mesophyll cells of the leaves. Chloroplasts are double membrane bound organelles in which the inner membrane is less permeable than the outer one. The space inside the inner membrane is stroma in which flattened structures called thylakoids are present. These thylakoids are arranged in stacks - one upon the other, like the pile of coins. The thylakoids are connected through tubules known as stroma lamellae. The space which is enclosed by the membrane of the thylakoid is called lumen. Some enzymes are present in the stroma, which are required to synthesise carbohydrate and protein.

Chloroplast is the most commonly occurring plastid. It has three types –
> Chromoplasts - Chromoplasts are heterogeneous organelles to store and synthesise pigments in the plants. They are mostly present in flowering plants, leaves and fruits.
> Gerontoplast - Gerontoplasts are a type of chloroplast that is produced from a chloroplast that is going through senescence. In this type of chloroplast, thylakoid membrane is lost.
> Leucoplasts – Leucoplasts are colourless, non-pigmented organelles found in plants. Their main function is to store starch and oil. They are mostly present in roots, seeds and bulbs.

Note: Chloroplast has its own double stranded, circular DNA along with ribosomes. Chloroplasts cannot be produced by the plant cells and thus it must be inherited by the daughter cells from their parent cells during the process of cell division. Pigments of the chlorophyll are present in the thylakoids.