Q.Explain the structure of chloroplast with the help of a labelled diagram. OR Explain the structure of mitochondria with the help of a labelled diagram.

Plastids are found only in plant cells, so the answer is (C).

Many organelles are common to both plant and animal cells — the nucleus, ribosomes, mitochondria, endoplasmic reticulum and Golgi apparatus. A few, however, are characteristic of plant cells.

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Chloroplast DNA, like mitochondrial and bacterial DNA, is circular and double-stranded, which supports the endosymbiotic origin of chloroplasts.

Chloroplasts are semi-autonomous, double-membrane-bound organelles found in the matrix (stroma), containing their own small, circular, double-stranded DNA along with 70S ribosomes. This allows the chloroplast to independently synthesise some of its own proteins, and it also divides on its own, independent of the cell.

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Grana = the stacked thylakoid discs inside a chloroplast.

A chloroplast is bounded by a double membrane envelope and contains a matrix called the stroma. Within the stroma lie flattened, membranous sacs called thylakoids. A stack of many thylakoids, resembling a pile of coins, is called a granum (plural: grana), and adjacent grana are connected to each other by flat membranous tubules called stroma lamellae. The thylakoid membranes house chlorophyll, other pigments, and the electron transport chain proteins that carry out the light reactions of photosynthesis; the surrounding stroma contains the enzymes of the Calvin cycle (dark reactio …

Amyloplast is the leucoplast that stores starch (a carbohydrate).

Plastids are grouped by their pigment/storage content into chloroplasts (green, photosynthetic pigments), chromoplasts (fat-soluble coloured pigments like carotenoids), and leucoplasts (colourless, storage plastids). Leucoplasts are further divided by what they store:

• Amyloplasts store starch — the main storage carbohydrate in plants (e.g., in potato tubers, rice and wheat endosperm).
• Aleuroplasts store proteins.
• Elaioplasts store oils and fats (lipids). …

Quantasomes are the structural and functional photosynthetic units studded on the thylakoid membranes inside the chloroplast.

The chloroplast is a double-membrane plastid whose inner space (stroma) contains a system of flattened, membrane-bound sacs called thylakoids, stacked into grana. Electron microscopy shows the thylakoid membrane studded with small particles historically named quantasomes, each thought to contain the chlorophyll molecules and electron-transport components needed to carry out one unit of the light reaction of photosynthesis. Because these particles are physically embedded in the chloroplast's thylakoid membrane, quantasomes are l …

Among leucoplasts, proteins are stored in aleuroplasts.

Leucoplasts are colourless plastids of variable shape and size that store food materials. They are of three types based on what they store: amyloplasts store carbohydrates (starch, e.g. in potato), elaioplasts (oleosomes/lipidoplasts) store oils and fats, an …