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14 Cards in this Set
- Front
- Back
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Where is the best step to regulate a synthetic pathway?
Where would a good inhibitor be placed in a pathway? |
First step (most energy)
Final product (negative feedback, have enough of product so stop production) |
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4 Regulatory Strategies
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1. allosteric control (reversible) = cooperativity feedback inhibition
2. multiple forms = metabolism in tissues 3. reversible covalent modification = phosphorylation 4. proteolytic activation (irreversible) = caspases blood clotting |
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Allosteric Regulation
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-"other shap" regulation
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What central metabolic cofactor provides energy for:
-muscle contraction -maintainence of ionic gradients in NS biosynthesis |
ATP: currency of life
adenosine triphosphate -1 molecule traps 4 negative molecules in it (triphosphate, ribose sugar, adenine base) -hydrolyze to break it = release energy |
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Why does hydrolysis of ATP have large -ΔG?
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inorganic Phosphate can resonate (orthophosphate is low in energy)
-ATP is high energy bc it constrains 4 negative charges in small region -hydrolysis frees the negative charge to separate physically in space & go down in energy |
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Glycolysis
-what is needed? Gluconeogenesis -what is needed? |
Sugar-breakdown
-oxidizes glucose to pyruvate to produce ATP -Need: 2ADP, 2NAD+ -Produces: 2ATP, 2NADH Sugar-building -hydrolyzes ATP to make glucose -Uses: 4 ADP, 2 GTP, 2 NAD+ -Produces: 4 ATP, 2 GTP, 2 NADH |
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Why do regulated steps have large negative free energy?
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-large free energy = irreversible (not in equilibrium)
-Step 1 (glucose --> G-6-P) -Step 3 (fructose-6-P --> fructose-6-bisP) phosphofructokinase -Step 10 (phosphenolpyruvate -->pyruvate) |
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What is the key regulator of glycolysis?
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phosphofructokinase (PFK-1)
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Glycolysis enzyme phosphofructokinase.
1. what are activators? 2. what are inhibitors? |
1. F-2,6-BP, AMP
2. ATP, Citrate, H+, Lactate |
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Gluconeogenesis enzyme fructose1,6-BP.
1. what are activators? 2. what are inhibitors? |
1. citrate
2. F-2,6-BP, AMP |
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Rate of catalysis change of phosphofructokinase with increasing [Fructose 6-P]
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-hyperbolic curve
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At high [ATP] how does phosphofructokinase 2/ increasing [Fructose 6-P] react?
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sigmoidal (s-shaped) curve
-lowers PFK's affinity for Fructose 6-P |
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Describe Phosphofructokinase as a homotetramer that is allosterically regulated.
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R-State:
-bind of F1-6BP to active site favors R-state (relaxed) T-state: -subunit w/out bound F1-6BP favors T-state (tight conformation) |
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Activation of phosphofructokinase by fructose 2,6-BP
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-the sigmoidal velocity becomes hyperbolic in presence of fructose 2,6-BP
-ATP initially stimulates rxn -as [ATP] increases it acts as an allosteric inhibitor -inhibitory effect is reversed by frustose 2,6-BP |
