Chapter 7 – Cellular Respiration. Pathways I. Glycolysis and Fermentation A.Harvesting Chemical...

Chapter 7 – Cellular Respiration

Pathways

I. Glycolysis and Fermentation

A. Harvesting Chemical Energy1. 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 CO2 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 membrane2. Cristae – inner folds of membrane3. Matrix – space inside the inner membrane; contains enzymes.

B. Steps:1. Pyruvic acid + coenzyme A

Acetyl CoA + CO2

* 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 CO2, H+, and

ATP.

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

2. Citric acid releases CO2 + H+ 5-C compound

3. 5-C compound releases CO2 + 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 FADH2 transport chain

Video – Kreb’s Cycle

Video – Kreb’s Cycle

3. Electron Transport Chaina. Occurs on the cristae.b. Uses the NADH and FADH2 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:

O2 + 4 e- + 4 H+ 2 H2O

III. Summary of Aerobic Respiration C6H12O6 + 6 O2 6 CO2 + 6 H2O + ATP(Energy)

A. Energy Yield1) Glycolysis – 2 ATP2) Kreb’s Cycle – 2 ATP3) Electron Transport Chain – 34 ATP Total – 38 ATP

B. Efficiency38 x 12 kcal x 100% = 66%

686 kcal

Video – Electron Transport Chain

Video – Cellular Respiration

The End