Biochemistry ATP Synthesis Quiz

Which molecule is reduced to form NADH during the Krebs cycle?

What molecule is produced as a result of the decarboxylation of isocitrate?

Which step in the Krebs cycle involves the conversion of fumarate to malate?

What is formed when FAD is reduced during the Krebs cycle?

In which step of the Krebs cycle is carbon dioxide produced?

What is the main enzymatic function of fumarase in the Krebs cycle?

Which enzyme catalyzes the step involving the conversion of α-ketoglutarate to succinyl-CoA?

What role does CO2 play in the Krebs cycle?

Which reduction product of the Krebs cycle carries electrons to the electron transport chain?

During which step does the substrate-level phosphorylation occur in the Krebs cycle?

Krebs Cycle (Citric Acid Cycle)

Acetyl CoA enters the cycle, combining with oxaloacetate to form 6C citrate.
CoA is stripped from Acetyl CoA and recycled during the process.
Key enzymes, such as citrate synthase, facilitate reactions throughout the cycle.
NAD+ and FAD are reduced to NADH and FADH2, respectively, during various oxidation steps.
Completion of the cycle regenerates oxaloacetate, allowing the process to continue.

Electron Transport Chain

Occurs across the inner mitochondrial membrane, where oxygen acts as the final electron acceptor, producing H2O.
NADH generated from the Krebs cycle and glycolysis contributes significantly to ATP production.
Each NADH yields approximately 2.5 ATP; 8 NADH can produce around 20 ATP.
FADH2 produces about 1.5 ATP; 2 FADH2 yield approximately 3 ATP.
NADH from glycolysis (cytosolic) cannot enter the mitochondrial matrix directly due to impermeability of the inner mitochondrial membrane.

ATP Generation

Total ATP produced can vary between 26 to 28 ATP, depending on whether NADH or FADH2 is used for generating ATP through oxidative phosphorylation.
Substrate-level phosphorylation in the Krebs cycle contributes directly to ATP formation.

Additional Cycle Steps

Isocitrate undergoes oxidation and decarboxylation, losing CO2 to form α-ketoglutarate.
The cycle includes crucial steps involving the transfer of hydrogens and the formation of intermediate compounds such as fumarate.
Each step carefully regulates the conversion and utilization of energy carriers, vital for cellular respiration.

Test your knowledge on ATP synthesis and substrate-level phosphorylation. This quiz covers key concepts and reactions involving FAD, NADH, and ATP production. Challenge yourself and see how well you understand the biochemical processes involved in energy metabolism.