Sample 1Easy
On a paper chromatogram of leaf pigments, chlorophyll a appears as a band of colour
- A
yellow green
- B
bright or blue green
- C
yellow
- D
yellow to yellow-orange
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The answer is B.Paper chromatography separates leaf pigments into chlorophyll a (bright or blue green), chlorophyll b (yellow green), xanthophylls (yellow) and carotenoids (yellow to yellow-orange). Chlorophyll a is the chief pigment of photosynthesis.
- A.
Yellow green is the colour of chlorophyll b.
- C.
Yellow is the colour of xanthophylls.
- D.
Yellow to yellow-orange is the colour of carotenoids.
NCERT: Class 11 Biology, Chapter 11 (Photosynthesis in Higher Plants), How Many Types of Pigments are Involved in Photosynthesis?
Sample 2Medium
A graph plots two curves against wavelength from 400 nm to 700 nm on the x-axis. One curve is the light absorption by chlorophyll a. The other is the rate of photosynthesis. Both curves are high in the blue region and in the red region, and they fall low in between. The rate curve does not drop to zero between the peaks. Which conclusion does the graph support?
- A
Photosynthesis takes place equally at all wavelengths of visible light
- B
Most photosynthesis takes place in the blue and red regions, and chlorophyll a is the chief pigment; some occurs at other wavelengths too
- C
Photosynthesis takes place mostly in the green region of the spectrum
- D
Photosynthesis takes place only at the exact wavelengths where chlorophyll a absorbs
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The answer is B.The action spectrum of photosynthesis closely matches the absorption spectrum of chlorophyll a. Both peak in the blue and red regions, which shows chlorophyll a is the chief pigment. Some photosynthesis still happens at other wavelengths.
- A.
The rate curve has clear peaks in the blue and red regions, so photosynthesis is not equal at all wavelengths.
- C.
Both curves dip in the green region. Green light is the least absorbed, which is why leaves look green.
- D.
The rate stays above zero between the peaks, because accessory pigments absorb other wavelengths and pass the energy to chlorophyll a.
NCERT: Class 11 Biology, Chapter 11