Metabolism: Glycolysis, Krebs Cycle, and Electron Transport Chain (Key Concepts)

A set of practice flashcards covering glycolysis, regulatory enzymes, acetyl-CoA formation, the Krebs cycle, electron transport chain, ATP yield, and fermentation as described in the notes.

What enzyme acts as an allosteric inhibitor in glycolysis by altering the enzyme's active site when ATP levels are high?

Phosphofructokinase (PFK)

During glycolysis, which three-carbon sugar is produced from the cleavage of fructose-1,6-bisphosphate?

Glyceraldehyde-3-phosphate (G3P)

Which enzyme complex converts pyruvate to acetyl-CoA, producing NADH and CO2 in the mitochondria?

Pyruvate dehydrogenase complex (PDH)

Where in the cell does the citric acid (Krebs) cycle occur?

Mitochondrial matrix

In glycolysis, what two steps perform substrate-level phosphorylation to generate ATP?

Phosphoglycerate kinase (1,3-bisphosphoglycerate to 3-phosphoglycerate) and pyruvate kinase (phosphoenolpyruvate to pyruvate)

What happens to pyruvate if oxygen is scarce after glycolysis?

It is converted to lactate (lactic acid) through fermentation, regenerating NAD+.

Which molecule ultimately accepts electrons at the end of the electron transport chain?

Oxygen, forming water

Where do NADH and FADH2 deliver their electrons in cellular respiration?

To the electron transport chain in the inner mitochondrial membrane (NADH at Complex I; FADH2 at Complex II)

What is the process called that uses the proton gradient to synthesize ATP in mitochondria?

Oxidative phosphorylation (chemiosmosis)

What are the per-turn products of the citric acid cycle?

1 ATP, 3 NADH, 1 FADH2, and 2 CO2

What are the overall end products of glucose oxidation under aerobic conditions?

CO2 and H2O, with about 36–38 ATP produced per glucose

What is the role of acetyl-CoA in the citric acid cycle?

Delivers the acetyl group to the cycle by forming citrate with oxaloacetate; CoA is released after entry

During glycolysis, which energy carrier is produced when G3P is oxidized by glyceraldehyde-3-phosphate dehydrogenase?

NADH

What happens to NADH and FADH2 if oxygen is not available?

They accumulate in reduced form and the electron transport chain halts; fermentation regenerates NAD+ to allow glycolysis to continue