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Enzymes

Enzymes. There are different types of enzymatic reactions. Many things can influence an enzymatic reaction LIKE WHAT??. Effect of Temperature. Enzymes often have a narrow range of conditions under which they operate properly.

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Enzymes

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  1. Enzymes

  2. There are different types of enzymatic reactions • Many things can influence an enzymatic reaction • LIKE WHAT??

  3. Effect of Temperature • Enzymes often have a narrow range of conditions under which they operate properly. • Enzyme activity increases with temperature, until the temperature is too high for the enzyme to function. (See diagram right). • At this point, enzymedenaturation occurs and the enzyme can no longer function. Optimum temperature for the enzyme Rapid denaturation at high temperatures Too cold for the enzyme to operate Rate of reaction Temperature (°C)

  4. Effect of pH 1 2 3 4 5 6 7 8 9 10 • Enzymes can be affected by pH. • Enzymes are found in very diverse pH conditions, so they must be suited to perform in these specialist environments. • Pepsin is a stomach enzyme • Urease breaks down urea and has an optimal pH of near neutral Trypsin Urease Pepsin Enzyme activity Acid Alkaline pH Enzymes often work over a range of pH values, but all enzymes have an optimum pH where their activity rate is fastest.

  5. Substrate/Enzyme concentrations affect the reaction rate Effect of Substrate Concentration Effect of Enzyme Concentration Rate of reaction Enzyme concentration Concentration of substrate Rate of reaction continues to increasewith an increase in enzyme concentration. This relationship assumes non-limiting amounts of substrate and cofactors. Rate of reaction increases and then plateaus with increasing substrate concentration. This relationship assumes a fixed amountof enzyme.

  6. Enzyme Cofactors • Nonprotein helpers that help catalyze reactions • Can either bind loosely or permanently on the substrate • If the cofactor is organic, it is considered a coenzyme • Vitamins are cofactors

  7. Vitamin C assists in the development of a healthy immune system Scurvy Spinal bifida Folic acid assists in spinal cord development Rickets disease Vitamin D- helps the absorption of calcium in blood, and production of phagocytes

  8. Enzyme Inhibitors • Two types • Competitive • Non-competitive • Many drug molecules are enzyme inhibitors.

  9. Competitive Inhibitors • Resembles the substrates • Blocks substrates from binding to active sites of enzymes • If we increase the substrate concentration, will the rate of reaction increase? • YES! – the chance of an enzyme interacting with an enzyme goes up • Example – penicillin – it blocks the enzyme of a bacteria involved in cell wall construction

  10. Competitive Inhibitors

  11. Non-competitive inhibitors Impede enzymatic reactions by binding on a part of the enzyme other than the active site Causes enzyme to change shape. How does this affect catalytic reactions? It can slow down, or won’t happen at all because the enzymes are basically denatured. If you increase the concentration of substrate will the rate of reaction increase? NO – the enzymes aren’t working to bind substrate!

  12. Non-competitive inhibitors

  13. Example of non-competitive inhibitor – Sarin nerve gas • Serine, found on the active site of acetylcholinesterase, an enzyme of the nervous system

  14. Allosteric Regulation • When a protein’s function at one site is affected by the binding of a regulatory molecule. • Can inhibit or stimulate activity

  15. Allosteric Regulation:In Detail • An enzyme prone to allosteric regulation has 2 or more protein subunits – each subunit has an active site • If one unit changes, everything else does, too!

  16. Active form Inactive form These ligands are often ATP or ADP molecules • This type of enzyme oscillates between 2 different shapes, depending on what types of ligand that binds to it • The binding of an effector molecule (ligand) can either enhance or decrease the action of that enzyme

  17. Why do we need allosteric regulation? • Allosteric regulation makes sure that our body does not produce too much of one thing. • Feedback inhibition • The product itself attaches to the first enzyme in the chain and inhibits the chain of reactions until they need to produce more of that product. • http://www.youtube.com/watch?v=M5bftq-W2aY

  18. Example: hemoglobin • Oxygen binding on just one subunit can increase the affinity to oxygen for all other subunits. • This is why there are more hemoglobin in areas of the body where respiration is needed most

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