Chapter 7: Cellular Respiration Flashcards
What is cellular respiration?
The process by which cells break down glucose and other organic molecules to produce ATP, using oxygen and releasing CO₂.
Write the overall equation for cellular respiration.
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
What are the three main stages of aerobic respiration?
Glycolysis → Citric Acid Cycle (Krebs Cycle) → Oxidative Phosphorylation (ETC + Chemiosmosis).
Where does glycolysis occur?
In the cytoplasm.
What are the inputs and outputs of glycolysis?
Inputs: 1 glucose, 2 ATP, 2 NAD⁺.
Outputs: 2 pyruvate, 4 ATP (net 2 ATP), 2 NADH.
Describe the energy investment and payoff phases of glycolysis.
Investment: 2 ATP are used to split glucose into two 3-carbon molecules.
Payoff: 4 ATP and 2 NADH are produced.
What enzyme catalyzes the rate-limiting step of glycolysis?
Phosphofructokinase (regulated by ATP/AMP levels).
What happens during pyruvate oxidation?
Pyruvate enters the mitochondrial matrix → converted to acetyl-CoA (releasing CO₂ and producing NADH).
List the inputs and outputs of the citric acid cycle.
Inputs per acetyl-CoA: 1 acetyl-CoA, 3 NAD⁺, 1 FAD, 1 ADP.
Outputs per acetyl-CoA: 2 CO₂, 3 NADH, 1 FADH₂, 1 ATP.
Why is the citric acid cycle called a ‘cycle’?
Oxaloacetate (4C) is regenerated to combine with acetyl-CoA (2C), forming citrate (6C).
What is the role of NADH and FADH₂ in the cycle?
They carry high-energy electrons to the electron transport chain (ETC).
Where is the electron transport chain (ETC) located?
Inner mitochondrial membrane (cristae).
Describe the role of oxygen in the ETC.
Final electron acceptor; combines with electrons and H⁺ to form water (O2 + 4H⁺ + 4e− → 2H2O).
What is chemiosmosis?
ATP synthesis driven by a proton gradient across the inner mitochondrial membrane. Protons flow through ATP synthase.
How much ATP is produced per glucose in oxidative phosphorylation?
~26-28 ATP (varies by cell type and shuttle used).
What is the function of ATP synthase?
Enzyme complex that uses proton flow to phosphorylate ADP → ATP.
What is fermentation?
Anaerobic process regenerating NAD⁺ by transferring electrons from NADH to pyruvate (no ETC).
Compare lactic acid and alcohol fermentation.
Lactic acid: Pyruvate → lactate (in muscles, bacteria).
Alcohol: Pyruvate → ethanol + CO₂ (in yeast).
Why is fermentation less efficient than aerobic respiration?
It produces only 2 ATP per glucose (vs. ~30-32 ATP in aerobic respiration).
How do fats enter cellular respiration?
Glycerol enters glycolysis; fatty acids undergo beta-oxidation to acetyl-CoA for the citric acid cycle.
How do amino acids contribute to energy production?
Deaminated (NH₂ removed) → carbon skeletons enter glycolysis or the citric acid cycle.
What is beta-oxidation?
Breakdown of fatty acids into acetyl-CoA (produces NADH and FADH₂).
How is cellular respiration regulated by feedback inhibition?
High ATP inhibits phosphofructokinase (glycolysis) and pyruvate dehydrogenase (pyruvate oxidation).
What role does insulin play in carbohydrate metabolism?
Signals cells to take up glucose and store it as glycogen or fat.
What is the glycerol phosphate shuttle?
Transfers electrons from cytosolic NADH to FADH₂ in mitochondria (yields 1.5 ATP/NADH vs. 2.5 ATP via malate shuttle).
How does cyanide inhibit cellular respiration?
Blocks cytochrome c oxidase (Complex IV) in the ETC, halting ATP production.
Why do fats yield more ATP than carbohydrates?
Fatty acids have more C-H bonds → more acetyl-CoA and NADH/FADH₂.
What is the Cori cycle?
Lactate from muscles → liver → converted back to glucose via gluconeogenesis.
Explain the role of uncoupling proteins in thermogenesis.
UCP1 in brown fat dissipates the proton gradient, releasing heat instead of ATP.
