Aerobic Respiration: Glycolysis to ETC

Study Notes

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

Description

This quiz covers the key processes of aerobic respiration, including glycolysis, the link reaction, the Krebs cycle, and the electron transport chain. Test your understanding of the biochemical steps involved and the products generated in each phase of this vital metabolic pathway.