Photosynthesis Photorespiration and C4/CAM Pathways 2

Question 1

In C4 plants, which molecule(s) serve as the CO2 carrier transporting fixed carbon from mesophyll cells to bundle sheath cells?

Accepted Answer

Malate or aspartate

Answer

Pyruvate

Answer

Oxaloacetate

Answer

Phosphoenolpyruvate (PEP)

Question 2

CAM plants open their stomata primarily during which part of the day to minimize water loss?

Accepted Answer

Night

Answer

Midday

Answer

Early morning only

Answer

Late afternoon

Question 3

In CAM plants, CO2 collected at night is stored in vacuoles as which organic acid?

Accepted Answer

Malic acid (malate)

Answer

Oxaloacetate

Answer

Citric acid

Answer

Aspartic acid

Question 4

Which of the following plants is a classic example of CAM photosynthesis?

Accepted Answer

Prickly pear cactus (Opuntia)

Answer

Corn (Zea mays)

Answer

Sugarcane (Saccharum officinarum)

Answer

Spinach (Spinacia oleracea)

Question 5

What is the immediate substrate for PEP carboxylase in C4 and CAM plants?

Accepted Answer

PEP (phosphoenolpyruvate)

Answer

RuBP (ribulose-1,5-bisphosphate)

Answer

3-phosphoglycerate (3-PGA)

Answer

NADPH

Question 6

During the daytime in CAM plants, accumulated malate is decarboxylated to release CO2, which then enters which pathway?

Accepted Answer

The Calvin cycle (light-independent reactions)

Answer

Glycolysis

Answer

The light reactions

Answer

Photorespiration

Question 7

Compared to RuBisCO, PEP carboxylase has which key advantage in carbon fixation?

Accepted Answer

It has a much higher affinity for CO2 and has no oxygenase activity

Answer

It requires less ATP per carboxylation event

Answer

It produces NADPH directly during the carboxylation reaction

Answer

It functions exclusively in bundle sheath cells