C1.2 Cellular respiration

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ATP: the cell's energy currency components

Adenine + ribose + 3 phosphates; supplies immediate energy.

What is the chemical reaction for ATP hydrolysis?

$ATP \rightarrow ADP + Pi + energy$ (drives cellular work).

How does phosphorylation affect target molecules?

ATP donates a phosphate group (Pi) to targets, making them more reactive.

How is ATP replenished in the cell?

Constantly recycled by respiration (and photosynthesis in plants).

Examples of active transport powered by ATP

$Na^+/K^+$ pumps and proton pumps.

Examples of biosynthesis powered by ATP

DNA/RNA polymerization and peptide bond formation.

Examples of movement powered by ATP

Myosin power stroke and kinesin/dynein on microtubules.

Examples of cell work powered by ATP

Vesicle trafficking, mitosis, and cytokinesis.

What specific transport and movement processes does ATP power?

Endocytosis/exocytosis and chromosome movement.

Energy transfer from ATP to ADP

Hydrolysis (releases energy).

Energy transfer from ADP back to ATP

Condensation (requires energy).

Two ways ATP is produced in respiration

Substrate-level phosphorylation (Glycolysis/Krebs) and oxidative phosphorylation (ETC/chemiosmosis).

Definition of Cell Respiration

Controlled oxidation of organic compounds to make ATP.

Path of cell respiration with oxygen ($O_2$)

Glycolysis (cytosol) $\rightarrow$ link reaction + Krebs + ETC (mitochondrion), resulting in a large ATP yield.

Path of cell respiration without oxygen ($O_2$)

Glycolysis $\rightarrow$ fermentation to regenerate $NAD^+$.

Cell Respiration Table: Glycolysis

Location: Cytosol; Inputs: Glucose, 2 ATP, $2 NAD^+$; Outputs: 2 pyruvate, 2 NADH, 4 ATP; Net ATP: 2.

Cell Respiration Table: Link Reaction

Location: Matrix; Inputs: 2 pyruvate, $2 NAD^+$; Outputs: 2 acetyl-CoA, $2 CO_2$, 2 NADH; Net ATP: 0.

Cell Respiration Table: Krebs Cycle

Location: Matrix; Inputs: 2 acetyl-CoA, $6 NAD^+$, 2 FAD; Outputs: $4 CO_2$, 6 NADH, $2 FADH_2$, 2 ATP; Net ATP: 2.

Cell Respiration Table: ETC/OP

Location: Inner membrane; Inputs: 10 NADH, $2 FADH_2$, $O_2$; Outputs: $H_2O$, $NAD^+$/FAD recycled; Net ATP: 28-32.

Aerobic vs Anaerobic: Oxygen ($O_2$) requirement

Aerobic: Required; Anaerobic: Not required.

Aerobic vs Anaerobic: Site of reaction

Aerobic: Mitochondrion; Anaerobic: Cytosol.

Aerobic vs Anaerobic: Substrate used

Aerobic: Glucose, lipids, amino acids; Anaerobic: Glucose only.

Aerobic vs Anaerobic: ATP yield per glucose

Aerobic: High (~30); Anaerobic: Low (2).

Aerobic vs Anaerobic: End-products in humans

Aerobic: $CO_2 + H_2O$; Anaerobic: Lactate.

Effect of temperature on cell respiration rate

Increases to an optimum then decreases due to enzyme denaturation.

Effect of oxygen ($O_2$) availability on respiration rate

Limits the rate of aerobic respiration.

Effect of substrate type and concentration on respiration rate

Carbohydrates are fast; lipids are slow but energy-rich.

Effect of pH on cell respiration rate

Enzymes have narrow pH optima; rate drops outside this range.

How can the rate of respiration be tracked?

Via $O_2$ consumption or $CO_2$ production