BISC 130 - Chapter 7: Cellular Respiration

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-SOME MISSED NOTES

• Oxidations and reductions are coupled

  • Redox reactions

• H+ may be transfoerred along with e-

• Some organic molecules readily gain or lose electrons.

  • They're called 'electron carriers'

  • Ex: NAD+ (oxidized)

  • NADH (reduced)

• Electrons can be at a high or a low energy state.

Cellular Respiration

• The complete breakdown and oxidation of glucose to generate ATP.

• C6 H12 O6 + O2 --> CO2 + H20 + energy (ATP)

• Several stages of CR:

1. Glycolysis

   1. A 10-enzyme metabolic pathway.

   2. Glucose (6-Carbon) to Pyruvate (3-Carbon) + 2

   3. ATP is spent (ATP -> ADP + P) in initial steps but a net amount is generated (ADP + Pi -> ATP)

   4. NAD+ reduced to NADH

   1. Takes place in the cyptoplasm

   • *In Eukaryotes, all further steps occur in the mitochondria

1. Pyruvate Oxidation

   1. During Pyruvate Oxidation, Pyruvate is broken down, oxidized, attached to coenzyme A (CoA).

   2. This process releases CO2.

   3. Generates NADH

   4. Results in acetyl-CoA 

1. The Citric Acid Cycle

   1. Acetyl group (2-Carbons) is transferred from CoA to oxaloacetate (4-carbons) to form citrate (6-carbons).

1. In several steps, citrate is broken down and oxidized back to oxaloacetate (CO2 x2 released)

1. ATP generated

1. NADH generated

1. FAD reduced to FADH2

   1. Another electron carrier

1. Electron Transport Chain

   1. ETC

1. NADH and FADH2 are oxidized back to NAD+ and FAD

1. Their high-energy energy electrons are passed through a series of other electron carriers

   1. They lose energy with each transfer

      1. Finally transferred to O2 as low-energy electrons. This creates H20

1. Energy from these electrons is used to pump H+ across the membrane.

   1. This is Active Transport

   2. This creates a 'Proton Gradient'.

      1. H+ cannot diffuse across the membrane

1. ATP Synthase

   1. A large multi-protein complex.

1. It spans the membrane

1. It allows H+ (protons) to pass through, down their concentration gradient.

   1. Powers the rotation of stalk, which generates ATP.

   • *Proton gradient is required for this to work

   • *Most of ATP from cellular respiration is made here in the ATP Synthase.

Catabolism of Other Carbohydrates

• Broken to monosaccharides, enter glycolysis

Catabolism of Proteins

• Broken to amino acids, then enter glycolysis, pyruvate oxidation, or cytric acid cycle.

Catabolism of Lipids/Fatty-Acids

• Broken into 2-Carbon units, enter citric acid cycle.

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