How Many Types of Pigments Are Involved in Photosynthesis?
Every shade of green in a leaf — and every olive, yellow or faintly orange tint that appears as foliage ages — points to a mixture rather than a single colouring substance. When leaf material is separated by paper chromatography, the green we casually attribute to one pigment resolves into four distinct bands: chlorophyll a, chlorophyll b, xanthophylls and carotenoids.
This quiz tests the evidence behind that separation and the division of labour in photosynthesis:
- The colour of each pigment band in the chromatogram
- Why leaves show many shades of green, even on the same plant
- The absorption spectrum of chlorophyll a and the action spectrum of photosynthesis
- Why chlorophyll a is the chief pigment, and how accessory pigments widen the usable wavelengths and protect chlorophyll a from photo-oxidation
Read each question carefully — the reasoning is as much quantitative as descriptive.
Q1. A chromatographic separation of leaf pigments shows that the colour we see in leaves is due to how many pigments?
The lesson states clearly that leaf colour is not due to a single pigment but due to four pigments: chlorophyll a, chlorophyll b, xanthophylls and carotenoids.
Q2. Which technique is used in the lesson to separate leaf pigments of a green plant?
Paper chromatography separates the pigment mixture into its components, making the composition visible as a series of coloured bands.
Q3. In the chromatogram, chlorophyll a appears as which colour?
Chlorophyll a is described as bright or blue green in the chromatogram, distinguishing it from chlorophyll b which is yellow green.
Q4. In the chromatogram, chlorophyll b appears as which colour?
Chlorophyll b appears yellow green in the chromatogram, while chlorophyll a is bright or blue green.
Q5. Xanthophylls appear in the chromatogram as which colour?
Xanthophylls appear yellow, whereas carotenoids appear yellow to yellow-orange.
Q6. Carotenoids appear in the chromatogram as which colour?
Carotenoids appear yellow to yellow-orange, the warmest of the four bands described in the lesson.
Q7. Which pigment is described in the lesson as the most abundant plant pigment in the world?
The lesson asks which is the most abundant plant pigment in the world and then studies the absorption spectrum of chlorophyll a, the chief pigment associated with photosynthesis.
Q8. Chlorophyll a shows maximum absorption of light in which regions of the visible spectrum?
From the absorption spectrum of chlorophyll a, maximum absorption occurs in the blue and the red regions of the spectrum.
Q9. The action spectrum of photosynthesis shows that the maximum rate of photosynthesis occurs in which regions?
The wavelengths at which there is maximum absorption by chlorophyll a, i.e. the blue and red regions, also show a higher rate of photosynthesis.
Q10. On comparing the absorption spectrum of chlorophyll a with the action spectrum of photosynthesis, what does the lesson conclude?
The lesson asks whether there is a complete one-to-one overlap and shows that the match is close but not perfect; the small gap is where accessory pigments earn their place.
Q11. Which set of pigments is called the accessory pigments in the lesson?
Other thylakoid pigments like chlorophyll b, xanthophylls and carotenoids are called accessory pigments; chlorophyll a is the chief pigment.
Q12. What are the two key roles of the accessory pigments according to the lesson?
Accessory pigments absorb light and transfer the energy to chlorophyll a, enabling a wider range of wavelengths to be used and protecting chlorophyll a from photo-oxidation.
Q13. Accessory pigments absorb light and then transfer the energy to which pigment?
Accessory pigments absorb light and transfer the energy to chlorophyll a, the chief pigment associated with photosynthesis.
Q14. Why do leaves of the same plant show so many different shades of green?
The explanation is not that the plant manufactures different green substances at random, but that the visible colour is a composite of several pigments present in varying proportions.
Q15. Pigments are best defined in the lesson as substances that:
The lesson defines pigments as substances that have an ability to absorb light at specific wavelengths.