Chapter 7 – Cellular Respiration

Pathways

I. Glycolysis and Fermentation A.Harvesting Chemical Energy 1. Glycolysis – biochemical pathway in which glucose is converted to two molecules of pyruvic acid; 6-C  Two 3-C * Occurs in the cytoplasm.

Steps: 1.Glucose + 2 phosphates + 2 ATP  Fructose 1,6 biphosphate P-C-C-C-C-C-C-P 2.Fructose 1,6 biphosphate splits into two PGAL (G3P); P-C-C-C C-C-C-P

3.Two PGAL + 2 NAD +  2 biphosphoglycerate P-C-C-C-P P-C-C-C-P 4.2 biphosphoglycerate + 4 ADP  2 molecules pyruvic acid + 4 ATP C-C-C C-C-C

Pyruvic Acid (Pyruvate)

B.Energy Yield – Glycolysis 1) * 2 ATP were used * 4 ATP were produced * Net gain of 2 ATP * 2 NADH - will be used in the electron transport chain 2) Efficiency = Energy required Energy released = 2 x 12 kcal x 100% 686 kcal = 3.5 %

Glycolysis

C. Anaerobic Respiration – pathway which occurs without oxygen. * yeast and bacteria cells. * cells that become deprived of oxygen. * occurs in the cytoplasm.

Anaerobic Respiration

1. Fermentation – converting pyruvic acid into other compounds without oxygen. Types: a. Lactic Acid Fermentation Pyruvic Acid + 2 H +  Lactic Acid 3-C

1) Importances * Foods – i.e. yogurt; cheese * Fatigued muscle cells

b.Alcoholic Fermentation Pyruvic Acid loses CO 2  Acetylaldehyde 2-C Acetylaldehyde + 2 H +  Ethyl Alcohol 2-C

1)Importances * Bread products * Beer, wine, and spirits industry

Anaerobic Respiration

II.Aerobic Respiration – producing energy with oxygen. A. Occurs in the mitochondrion. 1. Outer membrane 2. Cristae – inner folds of membrane 3. Matrix – space inside the inner membrane; contains enzymes.

B.Steps: 1. Pyruvic acid + coenzyme A  Acetyl CoA + CO 2 * 2-C * occurs in the matrix * Produces 2 NADH – will be used in the electron transport chain

2.Kreb’s Cycle – biochemical pathway that breaks down Acetyl CoA into CO 2, H +, and ATP.

Steps: 1.Acetyl CoA + oxaloacetic acid  Citric acid 6-C

2.Citric acid releases CO 2 + H +  5-C compound

3.5-C compound releases CO 2 + H +  4-C compound.

4.4-C compound releases H +  New 4-C compound

5.4-C Compound releases H +  Oxaloacetic acid; Kreb’s Cycle continues.

Net Yield: * 2ATP * 6 NADH used in the electron * 2 FADH 2 transport chain

Video – Kreb’s Cycle

3.Electron Transport Chain a. Occurs on the cristae. b. Uses the NADH and FADH 2 from glycolysis, the conversion of pyruvic acid  acetyl CoA, and the Kreb’s Cycle

c.Steps: 1) High energy electrons are passed along a series of molecules. 2) As the electrons move from molecule to molecule, the energy they lose is used to pump protons (H + ) from the matrix to the inner membrane.

3) A concentration gradient of H + drives the synthesis of ATP by chemiosmosis: ADP + P + ATP Synthase  ATP 4) Oxygen continues to accept electrons. This allows the ETC to continue: O e H +  2 H 2 O

III.Summary of Aerobic Respiration C 6 H 12 O O 2  6 CO H 2 O + ATP(Energy) A. Energy Yield 1) Glycolysis – 2 ATP 2) Kreb’s Cycle – 2 ATP 3) Electron Transport Chain – 34 ATP Total – 38 ATP

B.Efficiency 38 x 12 kcal x 100% = 66% 686 kcal

Video – Electron Transport Chain

Video – Cellular Respiration

The End