Glycolysis and Cellular Respiration

Glycolysis

• Definition: A metabolic pathway that converts glucose into pyruvate, yielding energy in the form of ATP and NADH.

• Key Steps:

  • Start with one molecule of glucose (C6H12O6).

  • End products include:

  • 2 molecules of 3-carbon Glyceraldehyde-3-phosphate (G3P).

  • 2 molecules of 3-carbon Pyruvate (C3H4O3).

• Energy Yield:

  • 2 ATP molecules produced per glucose.

Pyruvate Decarboxylation (to Acetyl-CoA)

• Location: Mitochondria (Specifically in the mito matrix).

• Process:

  • Each pyruvate (C3) is converted to Acetyl-CoA (C2) with the release of:

  • 2 molecules of Carbon Dioxide (CO2).

  • Reduction of NAD+ to NADH (2 NADH produced).

Citric Acid Cycle (Krebs Cycle)

• Initiation:

  • Acetyl-CoA (from pyruvate) enters the cycle.

• Key Outputs:

  • For each cycle (per Acetyl-CoA):

  • 1 Citrate (6C) is formed from Acetyl-CoA and oxaloacetate (4C).

  • Converts to Isocitrate (6C).

• Key Products:

  • 4 NADH (electrons carriers).

  • 1 FADH2.

  • 1 GDP (or ADP) which can be converted into ATP.

  • 2 CO2 released per cycle.

Electron Transport Chain (ETC)

• Location: Inner mitochondrial membrane.

• Components:

  • Utilizes electrons carried by NADH and FADH2.

• Key Steps:

  • 8 NADH and 4 FADH2 transferred to the electron transport chain.

  • Electrons pass through protein complexes, leading to the pumping of protons (H+) from the mitochondrial matrix to the intermembrane space.

• Result:

  • Establishes a proton gradient, contributing to ATP synthesis.

  • Yield of approximately 26-28 ATP depending on the efficiency of the system.

• Chemiosmosis refers to the process of ATP generation that occurs through the electrochemical gradient established by the electron transport chain.

  • Mechanism:

  • As electrons pass through the protein complexes of the ETC, protons (H+) are pumped from the mitochondrial matrix into the intermembrane space.

  • This creates a proton concentration gradient (proton-motive force) across the inner mitochondrial membrane.

  • ATP Synthase Function:

  • Protons flow back into the mitochondrial matrix through ATP synthase, a protein complex that harnesses this flow to convert ADP and inorganic phosphate (Pi) into ATP.

  • This process is an example of oxidative phosphorylation and is vital for ATP production in aerobic respiration.

  • Yield:

  • Approximately 26-28 ATP molecules are produced through chemiosmosis per glucose molecule, depending on the efficiency of the process and the organism.