MCAT citric acid cycle and electron transport key terms

What is the citric acid cycle?

A series of chemical reactions in mitochondria that generate energy through the oxidation of acetyl-CoA.

Key products of the citric acid cycle?

- 3 NADH - 1 FADH2 - 1 GTP (or ATP) - 2 CO2

True or False: Oxygen is directly used in the citric acid cycle.

False. Oxygen is not directly consumed; it is essential for the electron transport chain.

Fill in the blank: Acetyl-CoA enters the citric acid cycle by combining with _____ to form citrate.

oxaloacetate

NADH vs. FADH2: Which produces more ATP in the electron transport chain?

NADH produces approximately 2.5 ATP, while FADH2 produces about 1.5 ATP.

What enzyme converts citrate to isocitrate?

Aconitase.

Cause → Effect: Accumulation of NADH in the cell.

Inhibits the citric acid cycle and slows down metabolic processes.

How many times does the citric acid cycle turn per glucose molecule?

Twice, because one glucose produces two acetyl-CoA molecules.

What is the role of the electron transport chain?

To create a proton gradient that drives ATP synthesis via oxidative phosphorylation.

True or False: The citric acid cycle occurs in the cytoplasm.

False. It occurs in the mitochondrial matrix.

What are the two main stages of cellular respiration?

Glycolysis and aerobic respiration (which includes the citric acid cycle and electron transport chain).

Key cofactors required in the citric acid cycle?

- NAD+ - FAD - CoA

What happens to CO2 produced in the citric acid cycle?

It is expelled from the cell and eventually exhaled by the lungs.

Fill in the blank: The final electron acceptor in the electron transport chain is _____.

oxygen

What is the main function of the citric acid cycle?

The citric acid cycle generates NADH and FADH₂, which are crucial for ATP production.

True or False: The citric acid cycle directly produces ATP.

False - It primarily produces NADH and FADH₂ for oxidative phosphorylation.

Fill in the blank: Acetyl-CoA enters the citric acid cycle by combining with ____.

oxaloacetate.

How many NADH molecules are produced per cycle?

Three NADH molecules are produced in each turn of the cycle.

What are the end products of one turn of the citric acid cycle?

- 3 NADH - 1 FADH₂ - 1 ATP (or GTP) - 2 CO₂

Compare NADH and FADH₂ in the electron transport chain.

NADH donates electrons at Complex I; FADH₂ donates at Complex II, yielding different ATP amounts.

Cause → Effect: High ATP levels lead to ____.

Inhibition of the citric acid cycle.

What happens to electrons during oxidative phosphorylation?

Electrons from NADH and FADH₂ are transferred through electron carriers, ultimately reducing oxygen.

Which enzyme catalyzes the conversion of isocitrate to α-ketoglutarate?

Isocitrate dehydrogenase.

True or False: Oxygen is a direct reactant in the citric acid cycle.

False - Oxygen is not a direct reactant; it is used in the electron transport chain.

How is ATP generated in the electron transport chain?

Proton gradient created drives ATP synthase to produce ATP from ADP and inorganic phosphate.

What is the role of citrate synthase?

Citrate synthase catalyzes the first step of the citric acid cycle by forming citrate.

Name the four main enzymes that regulate the citric acid cycle.

- Citrate synthase - Isocitrate dehydrogenase - α-Ketoglutarate dehydrogenase - Malate dehydrogenase

What is the primary purpose of the electron transport chain?

To create a proton gradient for ATP synthesis and to reduce oxygen to water.