Glycolysis & Pyruvate Oxidation—Key Points

Glycolysis (overview)

• Glucose input: $C<em>6H</em>{12}O_6$ in the cytosol.

• Products per glucose:

  • 2 pyruvate molecules (each $C_3$)

  • Net ATP: $2$ (Gross ATP: $4$; 2 ATP used to activate glucose; 2 produced by substrate-level phosphorylation)

  • NADH: $2$

• Location: cytosol

• Key idea: Food energy is released in stages; visual diagrams help with recall and understanding where each step occurs.

Pyruvate oxidation (Acetyl-CoA synthesis)

• Location: mitochondrial matrix (between outer and inner membranes)

• Process: each pyruvate + CoA + NAD⁺ → acetyl-CoA + CO₂ + NADH

• Per glucose (two pyruvate):

  • Acetyl-CoA: $2$

  • CO₂: $2$

  • NADH: $2$

• Note: NAD⁺ is reduced to NADH during this step; acetyl-CoA enters the Krebs cycle in the matrix.

Mitochondrial context (structure and stages)

• Stage 2: transport from cytosol into mitochondria (formation of acetyl-CoA)

• Stage 3 and Stage 4: occur in the mitochondrial matrix (Krebs cycle) and inner-membrane processes (ETC) subsequently

• Matrix: the space inside the inner mitochondrial membrane; site of acetyl-CoA entry and many redox reactions

Per-glucose summary (glycolysis + pyruvate oxidation)

• Total ATP from glycolysis: $2$ net ATP (Gross $4$, minus $2$ used in activation)

• Total NADH from glycolysis: $2$

• NADH from pyruvate oxidation: $2$

• Total NADH per glucose (so far): $4$ before Krebs/ETC

• CO₂ released during pyruvate oxidation: $2$

• Acetyl-CoA produced per glucose: $2$

• Overall, from the first two stages per glucose: ATP, NADH, CO₂, and acetyl-CoA totals above

Quick study tips (based on the talk)

• Diagram the flow: show where each molecule is made and where it goes.

• Practice tracking oxidation state changes: which carbon atoms become CO₂ and which molecules are reduced (NAD⁺ → NADH).

• Remember the per-glucose numbers above; they tend to be consistent into higher-level biochemistry.