CLEP Biology Cellular Respiration and Photosynthesis 3

Question 1

What is the net ATP yield from the complete aerobic oxidation of one glucose molecule (theoretical maximum)?

Accepted Answer

30-32 ATP

Answer

Modern estimates place the net ATP yield at 30-32 ATP per glucose, accounting for the P/O ratio of the ATP synthase and the cost of transporting pyruvate and ADP/ATP across mitochondrial membranes.

Question 2

In C4 plants, where does initial CO2 fixation occur, and what is the first stable product?

Accepted Answer

Mesophyll cells; oxaloacetate (OAA)

Answer

In C4 plants, CO2 is initially fixed in mesophyll cells by PEP carboxylase to form oxaloacetate, a 4-carbon compound, which is then shuttled to bundle sheath cells.

Question 3

Which Complex of the electron transport chain is inhibited by cyanide?

Accepted Answer

Complex IV (cytochrome c oxidase)

Answer

Cyanide binds to the iron in the heme group of cytochrome c oxidase (Complex IV), blocking the final transfer of electrons to oxygen.

Question 4

The chemiosmotic theory proposes that ATP synthesis is driven by which gradient?

Accepted Answer

A proton (H+) electrochemical gradient across the inner mitochondrial membrane

Answer

Peter Mitchell's chemiosmotic theory holds that protons pumped across the inner mitochondrial membrane by the ETC create a proton-motive force that drives ATP synthase (Complex V).

Question 5

In the Calvin cycle, what is the immediate product after CO2 is fixed by Rubisco onto ribulose-1,5-bisphosphate (RuBP)?

Accepted Answer

Two molecules of 3-phosphoglycerate (3-PGA)

Answer

Rubisco catalyzes the carboxylation of RuBP (5C) with CO2, and the unstable 6-carbon intermediate immediately splits into two molecules of 3-phosphoglycerate (3C each).

CLEP Practice Test

CLEP Practice Test

CLEP Biology Cellular Respiration and Photosynthesis 3