Photosynthesis Cellular Respiration 3

Question 1

Which carbon compound enters the Krebs cycle to begin each turn?

Accepted Answer

Acetyl-CoA

Answer

Acetyl-CoA (a 2-carbon compound) combines with oxaloacetate at the start of each Krebs cycle turn, forming citrate.

Question 2

How many turns of the Krebs cycle are required to fully oxidize one glucose molecule?

Accepted Answer

2 turns

Answer

One glucose yields two pyruvates, each producing one acetyl-CoA, so the Krebs cycle runs twice per glucose.

Question 3

What is the role of coenzyme A (CoA) in cellular respiration?

Accepted Answer

It carries acetyl groups into the Krebs cycle

Answer

CoA forms acetyl-CoA by attaching to the 2-carbon acetyl group derived from pyruvate, delivering it to the Krebs cycle.

Question 4

Where in the cell does the Krebs cycle take place?

Accepted Answer

Mitochondrial matrix

Answer

The Krebs cycle enzymes are dissolved in the mitochondrial matrix, where the cycle reactions occur.

Question 5

Which Krebs cycle intermediate directly donates electrons to FAD to produce FADH2?

Accepted Answer

Succinate

Answer

Succinate is oxidized to fumarate by succinate dehydrogenase, which transfers electrons to FAD, producing FADH2.

Photosynthesis Practice Test