7.2.2 Link Reaction and Krebs Cycle

• What is the primary function of the Link Reaction?

  Convert pyruvate to acetyl-CoA
• The Krebs Cycle breaks down acetyl-CoA to generate NADH, FADH2, ATP, and CO2
• What is the input of the Link Reaction?

  Pyruvate
• What is the output of the Link Reaction?

  Acetyl-CoA, NADH, CO2
• What is the input of the Krebs Cycle?

  Acetyl-CoA
• What are the outputs of the Krebs Cycle?

  NADH, FADH2, ATP, CO2
• The Krebs Cycle generates more ATP directly than the Link Reaction.
• Where does the Link Reaction take place in the cell?

  Mitochondrial matrix
• Where does the Krebs Cycle occur in the cell?

  Mitochondrial matrix
• Both the Link Reaction and Krebs Cycle require oxygen directly to occur.

  False
• What are the two main electron carriers generated by the Krebs Cycle?

  NADH and FADH2
• The Link Reaction and Krebs Cycle are both essential steps in cellular respiration.
• Steps in the Link Reaction

  1️⃣ Pyruvate is decarboxylated

  2️⃣ Carbon dioxide is released

  3️⃣ NAD+ is reduced to NADH

  4️⃣ Coenzyme A combines with the remaining molecule

  5️⃣ Acetyl-CoA is formed
• The Link Reaction requires oxygen to convert pyruvate into acetyl-CoA.

  False
• What is the primary enzyme involved in the Link Reaction?

  Pyruvate dehydrogenase
• The Krebs Cycle directly generates more ATP than the Link Reaction.
• In which cellular component do both the Link Reaction and Krebs Cycle take place?

  Mitochondrial matrix
• Why is the mitochondrial matrix the ideal location for the Link Reaction and Krebs Cycle?

  It contains necessary enzymes
• What is the main purpose of the Link Reaction in cellular respiration?

  Converts pyruvate to acetyl-CoA
• The Krebs Cycle breaks down acetyl-CoA to generate NADH and FADH2
• Both the Link Reaction and Krebs Cycle occur in the mitochondrial matrix.
• Why is the location of the Link Reaction and Krebs Cycle in the mitochondrial matrix important?

  Provides necessary enzymes
• The Link Reaction links glycolysis to the Krebs Cycle.
• The Link Reaction and Krebs Cycle are crucial for cellular respiration.
• Steps of the Link Reaction

  1️⃣ Decarboxylation

  2️⃣ Oxidation

  3️⃣ Acetyl-CoA Formation
• What is the overall reaction of the Link Reaction?

  Pyruvate + CoA + NAD^ + \rightarrow Acetyl - CoA + CO_{2} + NADH</latex>
• Pyruvate enters the mitochondrial matrix during the Link Reaction.
• Match the step of the Krebs Cycle with its output:

  Condensation ↔️ Citrate

  First Decarboxylation ↔️ α-ketoglutarate, CO2, NADH

  Substrate-Level Phosphorylation ↔️ Succinate, ATP/GTP

  Oxidation ↔️ Fumarate, FADH2
• In the Krebs Cycle, malate is oxidized to regenerate oxaloacetate.
• Which enzyme catalyzes the regeneration of oxaloacetate in the Krebs Cycle?

  Malate dehydrogenase
• The Krebs Cycle occurs in the mitochondrial matrix.
• In the Krebs Cycle, citrate is converted to isocitrate.
• What are the outputs of the first decarboxylation step in the Krebs Cycle?

  α-ketoglutarate, CO2, NADH
• Major steps of the Krebs Cycle

  1️⃣ Condensation

  2️⃣ Isomerization

  3️⃣ First Decarboxylation

  4️⃣ Second Decarboxylation

  5️⃣ Substrate-Level Phosphorylation

  6️⃣ Oxidation

  7️⃣ Hydration

  8️⃣ Regeneration of Oxaloacetate
• In the oxidation step of the Krebs Cycle, succinate is oxidized to form fumarate
• Which enzyme catalyzes the oxidation of succinate to fumarate?

  Succinate dehydrogenase
• Fumarate is hydrated to form malate in the hydration step of the Krebs Cycle.
• In the regeneration of oxaloacetate, malate is oxidized to produce oxaloacetate and NADH
• Where does the Krebs Cycle occur in the cell?

  Mitochondrial matrix
• Order the first four steps of the Krebs Cycle:

  1️⃣ Condensation

  2️⃣ Isomerization

  3️⃣ First Decarboxylation

  4️⃣ Second Decarboxylation