BioInteractive Photorespiration and Alternative Carbon Fixation 3

Question 1

Which pathway do C4 plants use to regenerate PEP in the mesophyll cells?

Accepted Answer

Pyruvate is phosphorylated by pyruvate-phosphate dikinase (PPDK) to regenerate PEP

Answer

In C4 plants, pyruvate returned from bundle sheath cells is converted back to PEP by PPDK in the mesophyll, using ATP.

Question 2

What are bundle sheath cells in C4 plants?

Accepted Answer

Cells surrounding vascular bundles where the Calvin cycle and high CO2 concentrations are maintained

Answer

Bundle sheath cells in C4 plants are tightly packed around the vascular bundles and receive concentrated CO2 from 4-carbon acids delivered by mesophyll cells.

Question 3

How does Kranz anatomy in C4 plants support their photosynthetic strategy?

Accepted Answer

It creates two distinct cell types (mesophyll and bundle sheath) that spatially separate initial CO2 fixation from the Calvin cycle

Answer

Kranz anatomy provides the structural framework for the CO2 concentrating mechanism by physically separating primary CO2 capture (mesophyll) from RuBisCO-driven fixation (bundle sheath).

Question 4

What molecule transports concentrated CO2 from mesophyll to bundle sheath cells in many C4 plants?

Accepted Answer

Malate

Answer

In many C4 plants, oxaloacetate is converted to malate in the mesophyll, which is then transported to bundle sheath cells where it is decarboxylated to release CO2.

Question 5

What evolutionary advantage do C4 plants have over C3 plants during drought?

Accepted Answer

C4 plants achieve greater water-use efficiency because less CO2 loss occurs per water molecule transpired

Answer

The CO2-concentrating mechanism of C4 plants allows them to fix more carbon per water molecule transpired, giving them superior water-use efficiency in dry conditions.

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive Photorespiration and Alternative Carbon Fixation 3