Pyruvate Oxidation or Oxidative Decarboxylation (if oxygen is present

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Pyruvate Oxidation or Oxidative
Decarboxylation(if oxygen is present)

• The following occurs for each pyruvate
• CO2 removed.
• NAD reduced to NADH and the 2-carbon
  compound becomes acetic acid.
• Coenzyme A (CoA) attaches to acetic acid to form
  acetyl-CoA.

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Pyruvate Oxidation or Oxidative Decarboxylation
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Pyruvate Oxidation or Oxidative Decarboxylation

• Energy Yield Products
• 2 NADH
• 2 acetyl-CoA
• 2 CO2 (released as waste)

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Acetyl-CoA

• CoA comes from vitamin B5
• Proteins, lipids, and carbohydrates are
  catabolized to acetyl-CoA
• It can be used to make fat or ATP
• ATP determines what pathway this molecule takes
• If O2 is present, acetyl CoA moves to the
  Krebs Cycle (aerobic respiration)
• If O2 is NOT present, acetyl CoA becomes
  lactate (anaerobic respiration / fermentation)

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Krebs cycle - overview

• 8 step process, with each step catalyzed by a
  specific enzyme
• It is a cycle because oxaloacetate is the
  product of step 8, and the reactant in step 1
• REMEMBER Two acetyl-CoA molecules enter, so the
  Krebs Cycle must happen TWICE for every one
  molecule of glucose that begins glycolysis

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The Krebs Cycle
Occurs twice for each molecule of glucose, 1 for
each acetyl-CoA.
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The Krebs Cycle Key Features

1. In step 1, acetyl-CoA combines with oxaloacetate
   to form citrate.
2. NAD is reduced to NADH in steps 3, 4 and 8.
3. FAD is reduced to FADH2 in step 6.
4. ATP if formed in step 5 by substrate-level
   phosphorylation. The phosphate group from
   succinyl-CoA is transferred to GDP, forming GTP,
   which then forms ATP.
5. In step 8, oxaloacetate is formed from malate,
   which is used as a reactant in step 1.
6. CO2 is released in steps 3 and 4.

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The Krebs Cycle

• Energy Yield Products
• 2 ATP
• 6 NADH
• 2 FADH2
• 4 CO2 (released as waste)

NADH and FADH2 carry electrons to the electron
transport chain for further production of ATP by
oxidative phosphorylation.
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Cellular Respiration so far has produced

• Glycolysis
• 2 ATP (net)
• 2 NADH, converted to 2 FADH2
• Pyruvate Oxidation
• 2 NADH
• Krebs Cycle
• 2 ATP
• 6 NADH
• 2 FADH2

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E.T.C. - Structure

• A series of electron acceptors (proteins) are
  embedded in the inner mitochondrial membrane.
• These proteins are arranged in order of
  increasing electronegativity.
• The weakest attractor of electrons (NADH
  dehydrogenase) is at the start of the chain and
  the strongest (cytochrome oxidase) is at the end.
  
• Since the mitochondrial membrane is highly
  folded, there are multiple copies of the ETC
  across the membrane

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Electron Transport Chain - Overview

• NADH and FADH2 transfer electrons to proteins in
  the inner mitochondrial membrane
• The weakest electron attractors are at the start,
  and the strongest are at the end
• Each component is REDUCED, and then subsequently
  OXIDIZED
• Oxygen (highly electronegative) oxidizes the last
  ETC component
• The energy released, moves H atoms (i.e.
  protons) across mitochondrial membrane

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Electrochemical gradient is created, with a lot
of H outside
Sets the rate of this process
The energy stored in the gradient will be used
in the second part of the ETC to power ATP
synthesis
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