Question

Chlorophyll occurs in chloroplast:
a. Inner membrane
b. Thylakoid membrane
c. Outer membrane
d. Stroma

Answer 1

Hint: Plastids are found in all plant cells and euglenoids etc. these are of their main types: - leucoplasts, chromoplasts, and chloroplasts. Chloroplasts are greenish plastids which possess photosynthetic pigments, chlorophyll and carotenoids and take part in the synthesis of food. The majority of the chloroplasts of the green plants are found in the mesophyll cells of the leaves.

Complete answer:
In photosynthetic eukaryotes, photosynthesis occurs in the subcellular organelle known as the chloroplast. This double membrane-enclosed organelle possesses a third system of membranes called thylakoids. A stack of thylakoids forms a granum. Adjacent grana are connected by unstacked membranes called stroma lamellae. The fluid compartment surrounding the thylakoids called the stroma. There is a clear division of labour within the chloroplast.
- Proteins and pigments (chlorophylls and carotenoids) that function in the photochemical events of photosynthesis I.e, trapping the light energy and synthesis of ATP and NADPH, are embedded in the thylakoid membrane.
- In the stroma, enzymatic reactions incorporate carbon dioxide into plants leading to the synthesis of sugar, which in turn forms starch.

Hence, the correct answer is option (B).

Additional information:
> Chlorophyll Pigment: Chlorophyll has a tadpole-like structure. It consists of a porphyrin head and a phytol tail.
> Porphyrin head:
- All chlorophylls have a complex ring structure chemically related to the porphyrin like groups found in haemoglobin and cytochromes.
- Site of the electrons rearrangements when the chlorophyll is excited.
- A cyclic tetrapyrrolic structure with non-ionic magnesium atoms.
> Phytol tail:
- A long hydrocarbon tail is almost always attached to the ring structure.
- Anchors the chlorophyll to the hydrophobic portion of the thylakoids.

Note: The space enclosed by the inner membrane of the chloroplast is called the stroma. The stroma contains a large number of organised flattened membranous sacs called thylakoids which are arranged in stacks like piles of coins called grana or the intergranal thylakoid.