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| Metabolic pathways consist of... | chains and cycles of enzyme catalyzed reactions |
| Whats the induced fit model? | This is an extension of the lock-and-key model. It accounts for the broad specificity of some enzymes. In the induced fit model of enzymes the active size of the enzymes does not fit perfectly with the substrate as a lock and key model would. The fit is not perfect, so when the substrate collides with the enzyme and enters the active site, the substrate is stressed which allows its bonds to break easier. When another collision occurs with the substrate in the active site the bonds are broken and the substrate is released. Enzymes process these reactions very quickly |
| What do enzymes do to the activation energy? | lower it |
| How do enzymes lower the activation energy of the chemical reactions that they catlyze? | Heat speeds up a reaction, but high temperature denatures proteins and kills cells. Organisms use a catalyst instead. An enzyme speeds a reaction up by lowering the activation energy barrier so that the precipice of the transition state is within reach even at moderate temperatures. Enzymes can only hasten reactions that would occur eventually anyway. |
| What is competitive inhibition? | Competitive inhibition is a molecule that mimics a substrate and competes for the active site. An example is Penicillin because it blocks the active site in the enzyme that bacteria use to make cell walls. Another example is hemoglobin. |
| What is non-competitive inhibition? | Non-competitive inhibition binds away from the active site, changes the conformation (shape) of the enzyme which then does not allow the substrate to bind. An example is sarin gas because it binds to acetyl cholinesterase which is an enzyme in the nervous system. Both these forms of inhibition block enzyme activity |
| What does an endergonic and exergonic graph look like? | figures 6.13 and 6.13 |
| Whats the role of allostery in the control of metabolic pathways by end-product inhibition? | Allostery is a non-competitive inhibitor. The shape of allosteric enzymes can be altered by the binding of end products to an allosteric site, decreasing its activity. Metabolites can act as allosteric inhibitors of enzymes earlier in a metabolic pathway and regulate metabolism according to the requirements of organisms; a form of negative feedback. Some examples are ATP inhibition of phosphofructokinase in glycolysis and inhibition of aspartate carbamoyltransferase (ATCase) which catalyses the first step in pyrimidine synthesis. |
