Biochemistry Notes: FAD, Citric Acid Cycle, and Electron Transport Chain

FAD (Flavin Adenine Dinucleotide)

  • Derived from Riboflavin (Vitamin B2).
  • Vitamin B2, found in B-complex vitamins and energy drinks, aids in energy production by forming cofactors for ATP synthesis.

Citric Acid Cycle (Krebs Cycle or TCA Cycle)

  • Consists of 8 steps.
  • Produces:
  • 3 NADH
  • 1 FADH2
  • 2 CO2 (not explicitly mentioned in list but produced)
  • Key intermediates: Citrate, Isocitrate, Alpha-ketoglutarate, Fumarate, Malate, Oxaloacetate.
  • Driven by 7 enzymes with various byproducts.
  • Exercise science utilizes this cycle for manipulation.

Total Tally (Per Cycle)

  • 2 CO2
  • 3 NADH
  • 1 FADH2
  • Per Glucose Molecule: Multiply the per cycle values by 2, as glucose leads to two cycles.

Electron Transport Chain (ETC)

  • Location: Inner membrane of the mitochondria.
  • Coenzyme Q10 Function: Operates within the ETC.
  • NADH and FADH2 role: Donate hydrogen ions
  • Process:
  • NADH donates a hydrogen.
  • Hydrogen ions are pumped from the mitochondrial matrix to the intermembrane space, creating a concentration gradient.

Oxidative Phosphorylation

  • Definition: Process where hydrogen ions flow back into the matrix through ATP synthase, driving ATP production from ADP.
  • ATP synthase enzyme is crucial for this process.
  • Energy Source: Potential energy gradient (like a water dam) drives ATP synthesis.
  • Electron Transport Chain vs. Oxidative Phosphorylation: ETC builds the hydrogen gradient; oxidative phosphorylation uses the gradient to produce ATP.

ATP Yield

  • Citric Acid Cycle Yield: 10 ATP (net yield after accounting for ATP used in the process).
  • Total ATP Yield: Approximately 36 ATP per glucose molecule (though some sources say 32 ATP).

Summary of Cellular Respiration

  • Glucose is converted into pyruvate.
  • Pyruvate enters the TCA cycle, generating reactants.
  • Reactants proceed to the electron transport chain.
  • Electron transport chain builds up hydrogen ions.
  • Oxidative phosphorylation produces the majority of ATP.

ATP Synthesis and Cell Death

  • ATP is not synthesized during cell death.
  • Rigor Mortis: Occurs due to the lack of ATP to release muscle contraction. Calcium is needed for muscle contraction, and ATP is required for relaxation.
  • Post-mortem stiffness: Calcium remains bound, causing sustained contraction until calcium eventually dissociates.
  • ATP is needed to relax muscle contraction; calcium is needed for muscle contraction.

Exam Review

  • Metabolism: Understand the definition.
  • Mitochondria: High-activity cells have more mitochondria.
  • Mitochondrial Membranes: Know the inner membrane, intermembrane space, outer membrane, and matrix functions.
  • Carbohydrate Digestion: Begins in the mouth with amylase.
  • Protein Digestion: Starts in the stomach.
  • Fat Digestion: Occurs in the duodenum with pancreatic lipase.
  • Polysaccharides: Broken down into monosaccharides.
  • CO2 Production: 2 CO2 per cycle.
  • NADH Production: 3 NADH per cycle.
  • FADH2 Production: 1 FADH2 per cycle.
  • TCA Cycle Purpose: To produce reactants (CO2, NADH, FADH2) for the electron transport chain.
  • Creatine Phosphate: Donates phosphate groups to muscles for quick ATP regeneration.
  • Enzyme Dependence: All processes are heavily dependent on enzyme activities.
  • Metabolic Rate: Dependent on demand (e.g., resting vs. active state).
  • Catabolic vs. Anabolic: Understand the difference.
  • Citric Acid Cycle Pathway: Circular pathway.
  • Favorable Reactions: Produce a higher amount of product compared to reactants (e.g., using 2 ATP to make 8 ATP).
  • Bile Production: In the liver; emulsifies fats.
  • Carbohydrate Digestion: Starts in the mouth with amylase.
  • Electron Transport Chain: NADH and FADH2 pump hydrogen ions, which flow down the gradient during oxidative phosphorylation to create ATP via ATP synthase.