5.7.2 Link reaction and Krebs cycle

• What are the three stages of aerobic respiration?

  Link reaction, Krebs cycle, ETC
• What is the energy yield of aerobic respiration?

  36-38 ATP
• Order the stages of aerobic respiration:

  1️⃣ Link reaction

  2️⃣ Krebs cycle

  3️⃣ Electron transport chain
• The link reaction occurs in the mitochondrial matrix.


  True
• What are the products of the link reaction?

  Acetyl CoA, NADH, CO2
• The link reaction releases CO2 during the decarboxylation step.

  True
• What are the three key processes of the link reaction?

  Decarboxylation, oxidation, combination with CoA
• CO2 is released as a waste product during the link reaction.


  True
• The oxidation step of the link reaction produces NADH
• Match the products of the link reaction with their roles:

  Acetyl CoA ↔️ Enters the Krebs cycle

  NADH ↔️ Generates ATP in ETC

  CO2 ↔️ Waste product
• The Krebs cycle occurs in the mitochondrial matrix.
• Aerobic respiration requires oxygen
• Match the waste products with the type of respiration:

  CO2 and H2O ↔️ Aerobic Respiration

  Lactic acid or ethanol ↔️ Anaerobic Respiration
• Why does aerobic respiration release more energy than anaerobic respiration?

  Fully oxidizes glucose
• Pyruvate is converted into acetyl CoA
• Match the stages of respiration with their location:

  Glycolysis ↔️ Cytoplasm

  Link reaction ↔️ Mitochondrial matrix
• What enzyme catalyzes the link reaction?

  Pyruvate dehydrogenase complex
• Acetyl CoA enters the Krebs cycle
• What molecule is formed by the combination of acetyl acid and coenzyme A in the link reaction?

  Acetyl CoA
• The link reaction is the first stage of aerobic respiration.

  False
• Where does the link reaction occur in aerobic respiration?

  Mitochondrial matrix
• The Krebs cycle is fueled by acetyl CoA produced in the link reaction.


  True
• What are the two main types of respiration?

  Aerobic and anaerobic
• Aerobic respiration yields approximately 36-38 ATP molecules, while anaerobic respiration yields only 2 ATP molecules.
• What enzyme is required in the link reaction to convert pyruvate into acetyl CoA?

  Coenzyme A
• What is the key product of glycolysis that enters the link reaction?

  Pyruvate
• What is the key reactant in the link reaction?

  Pyruvate
• Pyruvate is converted to acetyl CoA in the link reaction.
• During decarboxylation, pyruvate is converted to acetyl aldehyde and CO2.
• NADH produced in the link reaction is used in the electron transport chain.


  True
• The Krebs cycle takes place in the mitochondrial matrix.
• Steps of the Krebs cycle

  1️⃣ Acetyl CoA enters the cycle

  2️⃣ Citrate is oxidized

  3️⃣ Oxaloacetate is regenerated
• Match the molecules in the Krebs cycle with their roles:

  Acetyl CoA ↔️ Enters and is oxidized

  Oxaloacetate ↔️ Combines with acetyl CoA

  Citrate ↔️ Releases CO2, NADH, FADH2

  NADH ↔️ Electron carrier to ETC

  FADH2 ↔️ Another electron carrier to ETC
• What is the role of CO2 in the Krebs cycle?

  Waste product
• FADH2 is another high-energy electron carrier produced in the Krebs cycle.
• What are the main products of the Krebs cycle?

  CO2, NADH, FADH2
• Match the product of the Krebs cycle with its role:

  CO2 ↔️ Released as a waste product

  NADH ↔️ Electron carrier

  FADH2 ↔️ Another electron carrier
• Compare the link reaction and the Krebs cycle based on the table provided:

  1️⃣ Location: Both in the mitochondrial matrix

  2️⃣ Key Reactant: Pyruvate in the link reaction ||| Acetyl CoA in the Krebs cycle

  3️⃣ Key Products: Acetyl CoA, NADH, CO2 in the link reaction ||| NADH, FADH2, CO2 in the Krebs cycle

  4️⃣ Energy Released: Moderate in the link reaction ||| High in the Krebs cycle
• Anaerobic respiration requires oxygen.

  False
• Steps of the link reaction in aerobic respiration:

  1️⃣ Pyruvate from glycolysis enters the mitochondrial matrix

  2️⃣ Pyruvate is converted to acetyl CoA

  3️⃣ CO2 is released as a waste product

  4️⃣ NADH is produced