Cellular Respiration Quiz

Cellular Respiration

• Involves various metabolic pathways breaking down carbohydrates, other metabolites, and building up ATP.
• Consumes oxygen, producing CO2; is aerobic.
• Typically involves the complete breakdown of glucose into CO2 and H₂O.
• Net equation for glucose breakdown: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
• Glucose is high-energy, CO₂ and H₂O are low-energy molecules; respiration is exergonic (releases energy).
• Electrons removed from substrates by oxygen which combines with H+ to become water.
• Glucose is oxidized, and O₂ is reduced.
• Reactions release energy gradually, producing ATP.
• Rapid breakdown would result in mostly lost energy as non-usable heat.
• Glucose breakdown yields 36 or 38 ATP (depending on conditions); this preserves ~39% of available energy.
• More efficient than, for example, a car burning gasoline (~25% efficiency).

NAD+ and FAD

• Each metabolic reaction in respiration is catalyzed by a specific enzyme.
• NAD+ (nicotinamide adenine dinucleotide) accepts two electrons and a hydrogen ion (H+) forming NADH + H+.
• FAD also accepts electrons and H+ forming FADH₂.
• High-energy electrons from NADH and FADH₂ are typically carried to the electron transport chain.

Cellular Respiration Phases

• Glycolysis: Breakdown of glucose in the cytoplasm into two pyruvate molecules.
  • Releases enough energy for two ATP.
  • Is anaerobic (doesn't use oxygen)
• Preparatory reaction: Pyruvate enters the mitochondrion, oxidized to a two-carbon acetyl group, and releases CO₂. This occurs twice per glucose molecule.
• Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondrial matrix, producing NADH and FADH₂.
  • Also releases CO₂ and forms one ATP per cycle.
  • Turns twice per glucose
• Electron Transport Chain: Located in the inner mitochondrial membrane.
  • Carriers pass electrons sequentially, releasing energy stored to produce ATP.
  • Oxygen is the final electron acceptor, forming water.

Fermentation

• An anaerobic process occurring in the absence of oxygen.
• Consists of glycolysis plus the reduction of pyruvate (producing lactate or alcohol).
• Animal cells produce lactate.
• Yeasts produce ethyl alcohol and CO₂.
• NADH passes electrons to pyruvate, regenerating NAD+ for glycolysis.
• Fermentation provides quick bursts of ATP for certain activities, but yields less than respiration (2 ATP).
• Lactate build-up can lead to muscle fatigue and oxygen debt.

Inside the Mitochondria

• Preparatory reaction, citric acid cycle, and electron transport chain occur in the mitochondrion.

Mitochondria Structure

• Mitochondria have a double membrane.
  • Inner membrane is folded into cristae.
  • The fluid-filled space within the inner membrane is the matrix.
• The cristae and matrix contain the necessary enzymes for cellular respiration.

Energy Production

• Substrate-Level Phosphorylation: ATP produced during glycolysis and citric acid cycle.
• Electron Transport Chain and Chemiosmosis: Most ATP is synthesized during this step.
• Glucose Breakdown: Complete breakdown of glucose releases ~686 kcal, with ~36 to 38 ATP produced via respiration.
• Efficiency: Complete glucose breakdown yields ~39% (263 kcal/686 kcal).

Metabolic Pool

• Substrates serve as entry points for degradation and synthesis.
• Degradative reactions (catabolism) break down molecules (exergonic).
• Synthetic reactions (anabolism) build molecules (endergonic).
• Other molecules beside glucose are also broken down in catabolism such as fats into glycerol and fatty acids.

Chloroplasts and Mitochondria

• Chloroplasts and mitochondria have similarities but perform different functions.
• Photosynthesis produces carbs such as glucose utilizing the sun's energy
• Respiration converts these carbs into ATP using O² releasing CO².

Test your understanding of cellular respiration, including its metabolic pathways and the role of NAD+ and FAD. This quiz covers the breakdown of glucose, the production of ATP, and the significance of aerobic processes. Explore how energy is converted and conserved in biological systems.