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Photosynthesis in Higher Plants · Question 60

AIPMT 2005MCQMedium📈 Topic in 12% papers+4−1
1

Photosynthesis in C4 plants is relatively less limited by atmospheric CO2 levels because

  1. effective pumping of CO2 into bundle sheath cells
  2. RuBisCo in C4 plants has higher affinity for CO2
  3. four carbon acids are the primary initial CO2 fixation products
  4. the primary fixation of CO2 is mediated via PEP carboxylase.

Answer

(4) the primary fixation of CO2 is mediated via PEP carboxylase.

Solution

As per NCERT, in C4 plants the primary CO2 acceptor is PEP in the mesophyll cells, and the reaction is catalysed by PEP carboxylase (PEPcase).

PEP + CO2 PEPcase OAA

∵ PEP carboxylase has a very high affinity for CO2 (and no oxygenase activity), it fixes CO2 efficiently even at low atmospheric CO2 levels.

⇒ The C4 acid then releases CO2 in the bundle sheath cells, keeping CO2 high around RuBisCO.

∴ Photosynthesis is less limited by atmospheric CO2 because primary fixation is mediated via PEP carboxylase.

Note: RuBisCO of C4 plants is the same enzyme as in C3 plants; it does not have a higher affinity for CO2.

Answer: (4)

AIPMT 2005

Keep practising — Photosynthesis in Higher Plants

2

Chlorophyll in chloroplasts is located in

  1. Stroma
  2. Grana
  3. Pyrenoid
  4. Both (1) and (3)
AIPMT 2005
3

Chemiosmotic theory of ATP synthesis in the chloroplasts and mitochondria is based on

  1. Proton gradient
  2. Membrane potential
  3. Accumulation of Na+ ions
  4. Accumulation of K+ ions
AIPMT 2005
4

In C3 plants, the first stable product of photosynthesis during the dark reaction is

  1. malic acid
  2. oxaloacetic acid
  3. 3-phosphoglyceric acid
  4. phosphoglyceraldehyde
AIPMT 2004
5

Plants adapted to low light intensity have

  1. larger photosynthetic unit size than the sun plants
  2. higher rate of CO2 fixation than the sun plants
  3. more extended root system
  4. leaves modified to spines.
AIPMT 2004
6

Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants?

  1. Blue and green
  2. Green and red
  3. Red and violet
  4. Violet and blue.
AIPMT 2003
7

Which one of the following is wrong in relation to photorespiration?

  1. It occurs in chloroplast
  2. It occurs in day time only
  3. It is a characteristic of C4 plants
  4. It is a characteristic of C3 plants.
AIPMT 2003
8

In sugarcane plant 14CO2 is fixed to malic acid, in which the enzyme that fixes CO2 is

  1. ribulose bisphosphate carboxylase
  2. phosphoenolpyruvic acid carboxylase
  3. ribulose phosphate kinase
  4. fructose phosphate.
AIPMT 2003
9

Stomata of CAM plants

  1. are always open
  2. open during the day and close at night
  3. open during the night and close during the day
  4. never open.
AIPMT 2003
10

Which element is located at the centre of the porphyrin ring in chlorophyll?

  1. Calcium
  2. Magnesium
  3. Potassium
  4. Manganese
AIPMT 2003
11

Which one of the following concerns photophosphorylation?

  1. ADP + AMP Light energy ATP
  2. ADP + Inorganic PO4 Light energy ATP
  3. ADP + Inorganic PO4 ATP
  4. AMP + Inorganic PO4 Light energy ATP
AIPMT 2003

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