Photosynthetic Pigments: Chlorophyll a, b, Xanthophylls and Carotenoids
Biology · Photosynthesis in Higher Plants · NEET
A green leaf has four photosynthetic pigments, seen as bands on a paper chromatogram: chlorophyll a (blue-green), chlorophyll b (yellow-green), xanthophylls (yellow), and carotenoids (yellow to yellow-orange). Chlorophyll a is the main pigment; the other three are accessory pigments that pass light energy to it. Memory hook: "a is blue-green boss, b is yellow-green, x is yellow, carotenoid is orange" — ABXC = Blue-green, Yellow-green, Yellow, Orange.
The four leaf pigments separated by paper chromatography and their exact colours: chlorophyll a (blue-green, the main pigment), chlorophyll b (yellow-green), xanthophylls (yellow), and carotenoids (yellow-orange). Chlorophyll b, xanthophylls, and carotenoids are accessory pigments that hand light energy to chlorophyll a.
Your doubts, answered
What are the four main photosynthetic pigments in a leaf?
A leaf has four pigments. They are chlorophyll a, chlorophyll b, xanthophylls, and carotenoids. You can separate them by paper chromatography. NCERT lists exactly these four, so learn all four for NEET.
What is the colour of each pigment on a chromatogram?
Chlorophyll a is bright or blue-green. Chlorophyll b is yellow-green. Xanthophylls are yellow. Carotenoids are yellow to yellow-orange. NEET asks you to match the pigment to its colour, so remember these four colours exactly.
Which is the main pigment and which are accessory pigments?
Chlorophyll a is the chief (main) pigment. It traps light and drives the light reaction. Chlorophyll b, xanthophylls, and carotenoids are accessory pigments. They absorb extra colours of light and pass the energy to chlorophyll a.
What is the difference between chlorophyll and carotenoids?
Chlorophylls (a and b) are green pigments and contain magnesium and nitrogen. Carotenoids are yellow, orange, or red pigments with no nitrogen. Carotenoids also protect chlorophyll a from harm by strong light (photo-protection).
Are xanthophylls and carotenoids the same thing?
No, but they are related. Both belong to the carotenoid group. Xanthophylls contain oxygen and look yellow. Carotenes (pure carotenoids) have no oxygen and look yellow to yellow-orange, like the orange colour of a carrot. NEET treats them as separate rows in matching questions.
In which order do pigments appear in paper chromatography?
When you run leaf extract on paper, the pigments move different distances. Carotenes move fastest (top), then xanthophylls, then chlorophyll a, then chlorophyll b moves least. But for NEET, the colour of each pigment is asked more often than the order.
⚠️ The NEET trap ✗ Chlorophyll a is yellow-green and chlorophyll b is blue-green. ✓ Chlorophyll a is blue-green (the main pigment) and chlorophyll b is yellow-green (accessory). 🧠 Colours get swapped in NEET matching questions. Fix it: 'a' is the boss, so it gets the deeper blue-green; 'b' is the helper with the lighter yellow-green.
Real NEET questions
NEET 2023
Match List I with List II: A. Chlorophyll a, B. Chlorophyll b, C. Xanthophyll, D. Carotenoid | I. Yellow to yellow orange, II. Yellow green, III. Blue green, IV. Yellow
A · (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
B · (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
C · (A)-(III), (B)-(II), (C)-(IV), (D)-(I) ✓
D · (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
Solution: Chlorophyll a is blue-green (III), chlorophyll b is yellow-green (II), xanthophyll is yellow (IV), carotenoid is yellow to yellow-orange (I). So A-III, B-II, C-IV, D-I, which is option C. Source: NCERT Class 11 chapter on Photosynthesis.
NEET 2025
Match List I (Pigment) with List II (Colour): A. Chlorophyll a, B. Chlorophyll b, C. Xanthophylls, D. Carotenoids | I. Yellow-green, II. Yellow, III. Blue-green, IV. Yellow to Yellow-orange
A · A-I, B-II, C-IV, D-III
B · A-I, B-IV, C-III, D-II
C · A-III, B-IV, C-II, D-I
D · A-III, B-I, C-II, D-IV ✓
Solution: Chlorophyll a is blue-green (III), chlorophyll b is yellow-green (I), xanthophylls are yellow (II), carotenoids are yellow to yellow-orange (IV). So A-III, B-I, C-II, D-IV, which is option D. The colours stay the same; only the numbering changes each year, so learn the colour, not the number.
ReNEET 2026
Which pigment has an absorption peak at 700 nm in the photosynthetic reaction centre PS I (P700)?
A · Chlorophyll b
B · Chlorophyll a ✓
C · Xanthophylls
D · Carotenoids
Solution: The reaction centre of both photosystems is chlorophyll a. In PS I this chlorophyll a absorbs at 700 nm and is named P700. In PS II it absorbs at 680 nm (P680). Accessory pigments like chlorophyll b and carotenoids never form the reaction centre.
Solved Photosynthesis in Higher Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Which pigment is the most important for photosynthesis?
Chlorophyll a is the most important. It is the chief pigment and forms the reaction centre of both photosystems. The other three pigments only help by trapping extra light and passing energy to chlorophyll a.
Why does a leaf need more than one pigment?
Chlorophyll a cannot absorb every colour of sunlight. Accessory pigments (chlorophyll b, xanthophylls, carotenoids) absorb colours that chlorophyll a misses. This lets the plant use a wider range of light and make more food.
Do carotenoids protect the plant?
Yes. Carotenoids absorb extra light energy and pass it on safely. They protect chlorophyll a from damage by strong light. This role is called photo-protection and is important in bright sunlight.
Why do leaves turn yellow or orange in autumn?
Chlorophyll breaks down first when leaves age. The yellow xanthophylls and orange carotenoids were always present but were hidden by green chlorophyll. Once green fades, their colours show.
Is this topic important for NEET?
Yes, very important. NEET has repeatedly asked pigment-colour matching (2023, 2025) and the P700 reaction centre pigment (2026). Learn the four pigments and their exact colours to score easy marks.
Related concepts: Chlorophyll a vs Chlorophyll b: Colour and RoleAccessory Pigments: Why Plants Have More Than Chlorophyll aAction Spectrum vs Absorption Spectrum of PhotosynthesisReaction Centre: P680 (PS II) vs P700 (PS I)Photosystems PS I and PS II and the Light Harvesting Complex
