Glucose Metabolism
GLUCOSE OXIDATION EQUATION
Glucose + 6 O2 --> 6 CO2 + 6 H2O + Energy (ATP + heat)
- Most energy is generated in mitochondrial matrix
Common Abbreviations:
- ATP: adenosine triphosphate
- NADH: nicotinamide adenine dinucleotide
- FADH2: flavin adenine dinucleotide
- CoA: Coenzyme A
- Glycolysis
- Pyruvate decarboxylation
- Citric acid cycle (also known as the Krebs' cycle and the tri-carboxylic acid (TCA) cycle)
- Oxidative phosphorylation (electron transport chain & chemiosmosis)
- 1 glucose --> 2 pyruvate + 2 ATP + 2 NADH
- Anaerobic reaction: no O2 required
- Occurs in cytosol
Substrate level phosphorylation
- ATP generated from substrates in glycolysis and citric acid cycle
- NOT from oxidative phosphorylation via NADH or FADH2
- Pyruvate + CoA + NAD+ --> Acetyl-CoA + CO2 + NADH
- Occurs in mitochondrial matrix
- Glycolysis
- Pyruvate decarboxylation
- Citric acid cycle (also known as the Krebs' cycle and the tri-carboxylic acid (TCA) cycle)
- Oxidative phosphorylation (electron transport chain & chemiosmosis)
- 1 glucose molecule requires 2 citric acid cycle turns
- Input for each turn: 1 Acetyl CoA
- Output for each turn: 3 NADH + 2 CO2 + 1 ATP + 1 FADH2
- NADH & FADH2: electron transfer molecules for oxidative phosphorylation
- Occurs in mitochondrial matrix
Substrate level phosphorylation
- ATP generated from substrates in glycolysis and citric acid cycle
- NOT from oxidative phosphorylation via NADH or FADH2
- Input: 10 NADH + 2 FADH2 (from glycolysis, pyruvate decarboxylation & CAC)
- Generates 30-34 molecules of ATP per glucose
- Main energy-generating process in respiration
- Comprises electron transport chain and chemiosmosis
- Occurs on inner mitochondrial membrane
Electron transport chain
- Series of redox reactions
- Pumps proton from matrix into intermembrane space
- Generates electrochemical gradient for ATP synthesis via ATP synthase
- Contains several protein complexes (I through IV)
- NADH gives electrons to complex I
- FADH2 gives electrons to complex II
- Complex I, III, and IV pump H+ into intermembrane space (Complex II DOES NOT)
- Complex IV consumes 1 O2 (final e- acceptor) to produce 2 H2O
Chemiosmosis
- ATP synthase: harnesses energy in electrochemical gradient (generated by ETC) to synthesize ATP from ADP & Pi