Biology 1002B Lecture Notes - Lecture 11: Multiprotein Complex, Acetaldehyde, Acetyl Group

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18 Apr 2012
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Stages of Cellular Respiration (6.5-6.7a)
1. Glycolysis
Glucose pyruvate
10 steps, in the cytoplasm
2. Pyruvate Oxidation
1 step, in the matrix of the mitochondria
3. Krebs cycle (TCA cycle or Citric Acid cycle)
8 steps, in the matrix of the mitochondria
4. Electron Transport and Chemiosmosis
Many steps, in membrane of mitochondria
Summary of Stage One
First biochemical pathway to evolve no oxygen
needed takes place in all living cells
Substrate level phosphorylation enzyme requiring
10 steps, in cytoplasm
Starts with glucose (6C molecule)
Ends with 2 pyruvate (3C molecule)
Energy
o 4 ATP directly produced
o 2 ATP used
o 2 NADH produced (will go on to yield more ATP)
Why Phosphorylate?
o You make molecules more reactive
o Compartmentalize molecules
Phosphate group is negatively charged do not like to cross membranes
Energy Investment
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Energy Payoff
Summary of Stage Two
One step that brings pyruvate into the mitochondria using
a carrier protein
Pyruvate is oxidized (electrons removed)
CO2 is removed (decarboxylation reaction) (so now it is
acetyl, a 2C molecule)
Coenzyme, called coA is attached
Occurs TWICE (2 pyruvates are produced in glycolysis)
Pyruvate dehydrogenase complex: Refers to whole
complex of 3 enzymes which converts pyruvate into Acetyl CoA
Transition before Stage Three
Acetyl-coA is a key molecule in energy metabolism
Can also be made from lipids, proteins (when you are on a low carb diet)
Can be used to make fat if you have enough cell energy
This stage is the turning point for aerobic vs. anaerobic
Note: No O2 has been used yet
Note: Overall, only 2 ATP made
Disorders of Energy Metabolism
Lots of genes encoding enzymes in cellular metabolism
Inborn errors of metabolism can occur (severe)
o Pyruvate Dehydrogenase Deficiency
Can be treated
Causes severe mental retardation
Brain becomes ATP deprived
Overcome by ketogenic diet (High fat, adequate protein, low carbohydrate)
88% fat, 10% protein, 2% carbohydrate
o Enzyme mutations
Shifts in Ratios
o Lactate/Pyruvate Ratio
Lactate or ethanol
Dehydrogenase
Pyruvate Dehydrogenase
Complex
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Oxygen deprived environment
o ATP/ADP ratio
o NAD/NADH ratio
There are genes regulated by these ratios, hence they are important
Summary of Stage 3: Krebs Cycle
8 step, in matrix, cyclical process
Oxaloacetate the final product of step 8 is used as a reactant in step 1
By the end of the cycle the glucose is fully used 2CO2 are released for each acetyl-coA, or 4 CO2 for each
glucose
Per pyruvate
o Reactants
Oxaloacetate (4C molecule) + acetyl-coA (2C) + ADP + Pi + 2NAD + FAD
o Products
coA + ATP + 2NADH + 3H+ + FADH2 + 2CO2 + oxaloacetate (4C)
o Energy
1 ATP
3 NADH
1 FADH2
Per glucose
o Reactants
Oxaloacetate + acetyl-coA + ADP + Pi + 2NAD + FAD
Oxaloacetate + acetyl-coA + ADP + Pi + 2NAD + FAD
o Products
coA + ATP + 2NADH + 3H+ + FADH2 +
2CO2 + oxaloacetate
coA + ATP + 2NADH + 3H+ + FADH2 +
2CO2 + oxaloacetate
o Energy
2 ATP
6 NADH
2 FADH2
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