Aerobic Respiration: Glycolysis to ETC

Aerobic Respiration

Glycolysis

• Occurs in the cytoplasm.
• Converts 1 glucose molecule (6 carbon) into 2 pyruvate molecules (3 carbon).
• Involves 10 enzymatic steps.
• Produces:
  • 2 ATP (net gain)
  • 2 NADH
• Does not require oxygen.

Link Reaction

• Takes place in the mitochondrial matrix.
• Pyruvate from glycolysis is decarboxylated to form Acetyl-CoA.
• Produces:
  • 1 NADH per pyruvate (2 per glucose)
  • 1 CO2 per pyruvate (2 per glucose)
• Acetyl-CoA enters the Krebs Cycle.

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix.
• Acetyl-CoA is oxidized, releasing CO2.
• Involved Steps:
  • Condensation of Acetyl-CoA with oxaloacetate to form citrate.
  • Multiple steps create NADH and FADH2.
• Produces per Acetyl-CoA:
  • 3 NADH
  • 1 FADH2
  • 1 ATP (or GTP)
  • 2 CO2
• Runs twice per glucose molecule.

Electron Transport Chain (ETC)

• Located in the inner mitochondrial membrane.
• NADH and FADH2 donate electrons, which move through protein complexes.
• Creates a proton gradient across the inner membrane.
• Oxygen acts as the final electron acceptor, forming water.
• Results in ATP synthesis via ATP synthase.

ATP Production

• Total ATP from one glucose molecule through aerobic respiration:
  • Glycolysis: 2 ATP (net) + 2 NADH (5 ATP via oxidative phosphorylation)
  • Link Reaction: 2 NADH (5 ATP)
  • Krebs Cycle: 6 NADH (15 ATP) + 2 FADH2 (3 ATP) + 2 ATP
• Total: approximately 30-32 ATP molecules.
• Efficiency varies based on conditions and cell type.

Glycolysis

• Occurs in the cytoplasm of the cell
• Breaks down glucose into two pyruvate molecules
• Produces a net gain of 2 ATP molecules and 2 NADH molecules
• Does not require oxygen

Link Reaction

• Takes place in the mitochondrial matrix
• Converts pyruvate into Acetyl-CoA, releasing carbon dioxide
• Generates 1 NADH molecule per pyruvate molecule

Krebs Cycle

• Occurs in the mitochondrial matrix
• Oxidizes Acetyl-CoA, releasing carbon dioxide
• Produces 3 NADH, 1 FADH2, 1 ATP (or GTP), and 2 CO2 per Acetyl-CoA molecule
• Runs twice per glucose molecule

Electron Transport Chain

• Located in the inner mitochondrial membrane
• Electrons from NADH and FADH2 are passed along a series of protein complexes
• Creates a proton gradient across the inner mitochondrial membrane
• Oxygen acts as the final electron acceptor, forming water

ATP Production

• Aerobic respiration produces approximately 30-32 ATP molecules per glucose molecule
• ATP is generated through oxidative phosphorylation, which is driven by the proton gradient created by the electron transport chain
• The exact amount of ATP produced varies based on factors such as cell type and conditions

Aerobic Respiration

• Primary energy production method, requires oxygen
• Occurs within the mitochondria of eukaryotic cells

Glycolysis

• Occurs in the cytoplasm
• Breaks down glucose (6 carbons) into two pyruvate molecules (3 carbons each)
• Two phases:
  • Investment phase: Requires 2 ATP
  • Payoff phase: Generates 4 ATP (net gain of 2 ATP) and 2 NADH
• End Products: 2 Pyruvate, 2 ATP, 2 NADH

Link Reaction (Pyruvate Oxidation)

• Takes place in the mitochondrial matrix
• Consists of the conversion of each pyruvate (3 carbons) into acetyl-CoA (2 carbons)
• Decarboxylation: Releases CO2
• Reduction of NAD+ to NADH
• End Products (per glucose): 2 Acetyl-CoA, 2 NADH, 2 CO2

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix
• Acetyl-CoA enters the cycle, combining with oxaloacetate to form citrate
• A series of reactions regenerate oxaloacetate
• Substrates are oxidized, releasing CO2
• Produces NADH, FADH2, and ATP (or GTP)
• End Products (per glucose): 6 NADH, 2 FADH2, 2 ATP (or GTP), 4 CO2

Electron Transport Chain (ETC)

• Located in the inner mitochondrial membrane
• NADH and FADH2 donate electrons to the chain
• Electrons move through a series of proteins, releasing energy used to pump protons (H+) into the intermembrane space
• Creates an electrochemical gradient (proton motive force)
• Oxygen acts as the final electron acceptor, forming water
• ATP Production:
  • Chemiosmosis: Protons flow back into the matrix through ATP synthase, driving ATP synthesis
• End Products: Up to 34 ATP, water (H2O)

Summary of ATP Yield

• Glycolysis: 2 ATP (net)
• Link Reaction: 0 ATP (but produces NADH)
• Krebs Cycle: 2 ATP (or GTP)
• Electron Transport Chain: ~34 ATP
• Total ATP Yield: Approximately 36-38 ATP per glucose molecule