Cellular Respiration Phase 2 Quiz

Second Phase of Cellular Respiration

• The second phase oxidizes intermediates, yielding 2 NADH and 2 pyruvic acids (pyruvates).
• Each NADH can be converted into 3 ATP via oxidative phosphorylation in the electron transport chain (ETC).

Electron Transport Chain Complexes

• The electron transport chain involves a series of protein complexes embedded in the inner mitochondrial membrane.
• Key components include:
  • NADH: Supplies electrons to Complex I.
  • FADH2: Supplies electrons to Complex II.
  • FMN: Receives electrons from NADH in Complex I.
  • Fe-S: Iron-sulfur clusters transferring electrons to Q.
  • Q (Ubiquinone): Mobile electron carrier transferring electrons from Complexes I and II to Complex III.
  • Cytochrome c: Transfers electrons from Complex III to Complex IV.
  • Complex IV: Reduces oxygen to water, final electron acceptor.

Krebs Cycle (Citric Acid Cycle)

• Converts acetyl CoA into CO2, producing electron carriers (NADH, FADH2) and GTP/ATP.
• Key reactions:
  • Isocitrate is converted to α-ketoglutarate with NAD+ forming NADH.
  • α-Ketoglutarate is converted into succinyl CoA with CO2 release and NAD+ forming NADH.
  • Succinyl CoA is converted to succinate, generating GTP (or ATP).
  • Succinate is oxidized to fumarate, producing FADH2.
  • Fumarate is converted to malate, then back to oxaloacetate, producing NADH.

Major Outcomes of the Krebs Cycle

• Generates 2 CO2 molecules and transfers electrons to electron carriers through redox reactions.
• Produces energy via substrate-level phosphorylation.

Summary of Cellular Respiration

• Three major stages:
  • Glycolysis: Breakdown of glucose in the cytosol producing pyruvate.
  • Krebs Cycle: Further breakdown of pyruvate in mitochondrial matrix, yielding NADH, FADH2, and ATP.
  • Electron Transport Chain: High-energy electrons from NADH/FADH2 are passed down the chain, creating a chemiosmotic gradient to produce ATP.
• Total ATP yield from one glucose molecule ranges between 36 to 38.

Overview of ATP Synthesis

• ATP synthase utilizes the proton gradient to synthesize ATP from ADP and inorganic phosphate.
• Oxygen combines with electrons and hydrogen ions to form water, a byproduct of aerobic respiration.

Glucose Utilization

• Glucose (6-carbon) is broken down into two 3-carbon pyruvate molecules, eventually producing CO2 and ATP.
• CO2 is transported by blood to lungs for exhalation.

Importance of NADH and FADH2

• Vital electron carriers generated in glycolysis and the Krebs cycle; essential for ATP production in the ETC.

Mitochondrial Structure

• The mitochondrion comprises the intermembrane space, inner mitochondrial membrane, matrix with enzymes for Krebs cycle, and ATP synthetase for ATP production.

Test your knowledge on the second phase of cellular respiration. This phase involves the oxidation of substrates and the production of NADH and pyruvic acid. Understand the role of NADH in ATP production and the significance of the electron transport chain.