Why are c4 plants able to photosynthesize with no apparent photorespiration?
a) They are adapted to cold, wet climates.
b) They use a more efficient enzyme to initially fix CO2.
c) They do not carry out the Calvin Cycle.
d) They exclude oxygen from their tissues.
e) They conserve water more efficiently.
- b) They use a more efficient enzyme to initially fix CO2.
C4 plants are able to photosynthesize with no apparent photorespiration because they use a more efficient enzyme to initially fix CO2. The enzyme, PEP carboxylase, is found in the mesophyll cells of C4 plants and helps to convert CO2 into organic acids. These organic acids are then transported to the bundle sheath cells where they are used to produce ATP and NADPH. This process is known as the C4 cycle and it allows C4 plants to have a higher photosynthetic rate than C3 plants.
The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?
A) C4 plants allow less water loss, but CAM plants allow more water loss.
B) C4 compromises on water loss and CAM compromises on photorespiration.
C) CAM plants allow more water loss, while C4 plants allow less CO2 into the plant.
D) Both minimize photorespiration but expend more ATP during carbon fixation.
E) Each one minimizes both water loss and rate of photosynthesis.