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28 Cards in this Set
- Front
- Back
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location of synthesis
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liver
adipose tissue |
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First step in biosynthesis is the carbonxylation of acetyl CoA to form malonyl CoA, catalyzed by acetyl CoA carbonxylate
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Acetyl CoA+ HCO3‐+ ATP → MalonylCoA+ ADP + Pi
required energy endogornic reation |
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This cytosolicenzyme has biotin as cofactor and is inhibited by phosphorylationmediated by AMP‐dependent protein kinase: switched off when AMP levels are high
• Switched back on when ATP levels rise |
Acyl groups of cytoplasmic malonylCoA and acetyl CoA get transferred to Acyl carrier protein
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Acetyl ACP (2C) and MalonylACP (3C) react to form
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acetoacetylACP (4C) and CO2
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AcetoacetylACP then undergoes sucessivereduction, dehydration, and reduction to form
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butyrylACP
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ButyrylACP will react with malonylACP to start a second series of reactions, leading to the formation of
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a 6 carbon aliphatic fatty acylACP
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In mammals, ACP and enzymes catalyzing all steps are components |
of a single polypeptide chain
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Reduction reactions involve NADP+, not NADPH
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important to note
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Fatty acid biosynthesis occurs in cytosol, but acetyl CoAis produced in
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mitochondria (pyruvatedehydrogenase, fatty acid oxidation)
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Acetyl CoAcannot cross
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inner mitochondrial membrane
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When rate of TCA cycle is low (high ATP, NADH),
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citrate accumulates in mitochondria and is transported to cytosol
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In cytosol, citrate cleavage enzyme catalyzes
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formation of OAA and acetyl CoAfrom citrate:
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Citrate + ATP + CoA+ H2O → acetyl CoA+ ADP + Pi + OAA
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OAA → Malate
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Malate+ NADP+→
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pyruvate+ CO2+ NADPH
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Metabolism and real life
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Greg's life as an annecdote
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Tragic experience
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Both fat and carb can serve to provide energy but Carbohydrates (Glucose) is/are the body’s preferred source of energy
The only source of energy for the brain (blood‐brain barrier) and red blood cells (no mitochondria) High intensity exercise (sprinting) driven almost exclusively by anaerobic glycolysis Maximum sprint distance ~ 200m Pacing critical for longer distance races. |
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Tragic experience Tragic experience
Greg's 4 x 800m relay experience |
was in the lead for the first time ever.
He starts fsat He slow down He feels good He's hanging on He can barely walk in |
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was in the lead for the first time ever.
He starts fsat He slow down He feels good He's hanging on He can barely walk in |
WHat happened
Lactic acid build up early Slow down in pace allowed more aerobic metabolism in mid race Last 100m: need for muscle ATP acute, lactic acid build up leads to increase in muscle H+ High H+ inhibits PFK ( can't generate ATP) Glycolysis stops, muscles stop working. Pace yourselves in all thing. |
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Marathon: right pace, 75% calories from CHO, 25% from fat
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Maximum CHO energy storage: 2000 cHO
Maximum CHO energy storage: 2000 cals (good for 20 miles) As race goes on, CHO becomes depleted. If CHO gets depleted before race finishes you hit |
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The wall: CHO reserves depleted
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Need some CHO to faccillitate fatty acids break down
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Why ?
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OAA limiting for TCA cycle
Brain, RBC need glucose OAA used for glucoseneogenseis in liver. No way to provide muscles with adequate ATP to maintain pace. |
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ATkins diet
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Low CHO
average fat Protein rich |
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Rationale
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When low CHO, body uses fat as source of energy
Protein provides source of OAA, glucose through gluconeogensis.) |
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Side effect : Your breath smells bad. Why ?
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Low OAA in liver
FA's converted to acetyl CoA faster than acetyl CoA + OAA can form citrate Acetyl CoAs combine to form acetoacetate, beta-hydroxymalonate Relased as ketones into blood ACetatoacetate -> acetone, can be detected in breath |
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Overview of oxidative phosphorylation
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For every C2 enter the cycle, we have 3 NADH, FADH2 and GTP
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NADH and FADH2formed during cycle re‐oxidized to NAD+and FAD through action of respiratory or electron transport chain
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Respiratory chain transfers electrons to O2to form H20. Coupled to formation of H+gradient across inner membrane
Discharge of gradient coupled to ATP synthesis |
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Highly exergonic (large negative ΔG)
Captured as proton gradient across inner membrane ADP + Pi → ATP |
Over view
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Redox reaction
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Electron transfer chain: electrons transferred from one carrier to next
• Electron transfer involves both oxidation (loss of electrons) and reduction (gain of electrons) • Example: succinate + FAD →fumarate + NADH2 Can be considered as two half reactions: Succinate →fumarate + 2e‐+ 2H+(oxidation) FAD + 2e‐+ 2H+→FADH2 (reduction) Succinate + FAD + 2e‐+ 2H+→fumarate + FADH2+ 2e‐+ 2H+ Next reaction in chain: FADH2+ 2 Fe+3(NHI) →FAD + 2 Fe+2(NHI) + 2 H+ |
