Citric Acid Cycle Concepts

The citric acid cycle is crucial for cellular respiration, starting with citrate formation from acetyl-CoA and oxaloacetate. It involves oxidative decarboxylation, producing NADH, FADH2, and GTP. The cycle regenerates oxaloacetate, with carbon atoms tracked over multiple cycles. Intermediates play roles in anabolic processes, and the cycle compensates for lost molecules through anaplerotic reactions.

What is the initial molecule formed in the citric acid cycle?

• Isocitrate

• Citrate

• Oxaloacetate

• Alpha-ketoglutarate

Which molecule is reduced to form NADH during the first oxidative decarboxylation?

• GDP

• NAD+

• GTP

• FAD

Which molecule is formed when citrate is isomerized?

• Fumarate

• Isocitrate

• Malate

• Oxaloacetate

What is the product of succinate dehydrogenation?

• Oxaloacetate

• Citrate

• Fumarate

• Malate

What is the result of the conversion of succinyl-CoA to succinate?

• Formation of ATP

• Reduction of FAD

• Synthesis of GTP

• Release of CO2

Which molecule is directly involved in the hydration of fumarate?

• Water

• NAD+

• FAD

• GTP

How many cycles does it take to release both carbons of an incoming acetyl group?

• One cycle

• Four cycles

• Three cycles

• Two cycles

Which carbon is released during the first decarboxylation of the third cycle?

• Carbon 1

• Carbon 2

• Carbon 4

• Carbon 6

What role do intermediate molecules in the citric acid cycle play?

• They are stored for energy

• They participate in anabolic processes

• They are excreted as waste

• They are only used in the cycle

What is the purpose of anaplerotic reactions in the citric acid cycle?

• To release CO2

• To generate ATP

• To regenerate intermediates

• To produce water