Question

In higher plants, the light harvesting molecules are:

• A. Vitamin D and cytochrome C
• B. Cytochrome C and chlorophyll
• C. Anthocyanin and carotenoid
• D. Chlorophyll and carotenoid

Hint:

Chlorophyll absorbs light for photosynthesis, while carotenoids protect plants from light-induced damage and expand the range of light absorbed.

Answer 1

The Correct Option is D

Step 1: Understanding light harvesting molecules.
In higher plants, light harvesting molecules are pigments that absorb light and play a crucial role in photosynthesis. The primary pigments involved are chlorophyll and carotenoids. Chlorophyll absorbs light energy, while carotenoids assist by absorbing light in different spectra and protecting the plant from photo-damage.
Step 2: Analyzing the options.
(1) Vitamin D and cytochrome C: This is incorrect. Vitamin D and cytochrome C are not involved in light harvesting for photosynthesis.
(2) Cytochrome C and chlorophyll: This is incorrect. Cytochrome C is involved in cellular respiration, not light harvesting.
(3) Anthocyanin and carotenoid: This is incorrect. Anthocyanins are pigments involved in flower color and not light harvesting, although carotenoids are involved in light absorption.
(4) Chlorophyll and carotenoid: Correct — Chlorophyll and carotenoids are the two main light-harvesting molecules in plants, crucial for photosynthesis.
Step 3: Conclusion.
The correct answer is (4) Chlorophyll and carotenoid, as these are the primary pigments used in light harvesting in plants.

Answer 2

Light-harvesting molecules in plants must actually absorb light in the visible range and be located in the photosynthetic membranes. Checking each pairing against that requirement:

1. Vitamin D and cytochrome C: Vitamin D is a steroid-derived molecule involved in calcium metabolism in animals and has no role in plant photosynthesis. Cytochrome C is an electron-transport protein used in respiration, not light absorption. Neither belongs to the plant light-harvesting apparatus.
2. Cytochrome C and chlorophyll: Chlorophyll is a genuine light-harvesting pigment, but pairing it with cytochrome C is wrong because cytochrome C functions in electron transfer during respiration, not in capturing light energy.
3. Anthocyanin and carotenoid: Carotenoids are legitimate accessory light-harvesting pigments, but anthocyanins are water-soluble vacuolar pigments that colour petals and fruits; they play no role in funnelling light energy into the photosynthetic reaction centres.
4. Chlorophyll and carotenoid: Both sit within the thylakoid membrane and both absorb photons -- chlorophyll mainly in the blue and red regions, carotenoids in the blue-green region that chlorophyll absorbs poorly -- passing the captured energy on to the reaction centre.

Since only the fourth pairing consists of two genuine, membrane-bound, light-absorbing photosynthetic pigments, that is the correct choice.

Therefore, the correct answer is Chlorophyll and carotenoid.