What can you tell me about this picture?

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1 What can you tell me about this picture?

2 ENZYMES A protein with catalytic properties due to its power of specific activation

3 1. Anabolic reactions: Define the following terms: Reactions that build up molecules 2. Catabolic reactions: 3. Metabolism: 4. Catalyst: 5. Metabolic pathway: 6. Specificity: 7. Substrate: 8. Product: Reactions that break down molecules Combination of anabolic and catabolic reactions A substance that speeds up reactions without changing the produced substances Sequence of enzyme controlled reactions Only able to catalyse specific reactions The molecule(s) the enzyme works on Molecule(s) produced by enzymes

4 Usually end in -ase Type of protein Enzymes Used to speed up chemical reactions in the body Also called biological catalysts

5 In anabolic reactions enzymes bring the substrate molecules together. In catabolic reactions the enzyme active site affects the bonds in substrates so they are easier to break

6 Lock-and-key hypothesis assumes the active site of an enzyme is rigid in its shape How ever crystallographic studies indicate proteins are flexible.

7 The Induced-fit hypothesis suggests the active site is flexible and only assumes its catalytic conformation after the substrate molecules bind to the site. When the product leaves the enzyme the active site reverts to its inactive state.

8 Energy levels of molecules Enzymes lower the activation energy of a reaction Initial energy state of substrates Activation energy of enzyme catalysed reaction Activation energy of uncatalysed reactions Final energy state of products Progress of reaction (time)

9 Qualities of enzymes Reusable one enzyme can be used many times Specific enzyme has a specific folded SHAPE so that the active site only fits its intended substrate (ex. Lactase will only break down lactose, NOT sucrose)

10 Enzymes are globular proteins Active site has a specific shape due to tertiary structure of protein. A change in shape of the protein affects shape of active site and the function of the enzyme. Click to link to jmol interactive representation courtesy of University of Arizona

11 Denaturing an enzyme Enzymes may become denatured (destroyed) in harsh environments, such as incorrect ph and harsh temperature.

12 Making reactions go faster Increasing the temperature make molecules move faster Biological systems are very sensitive to temperature changes. Enzymes can increase the rate of reactions without increasing the temperature. They do this by lowering the activation energy. They create a new reaction pathway a short cut 2007 Paul Billiet ODWS

13 An enzyme controlled pathway Enzyme controlled reactions proceed 108 to 1011 times faster than corresponding non-enzymic reactions Paul Billiet ODWS

14 What Affects Enzyme Activity? 14 Three factors: 1. Environmental Conditions 2. Cofactors and Coenzymes 3. Enzyme Inhibitors

15 The effect of ph Optimum ph values Enzyme activity Trypsin Pepsin 2007 Paul Billiet ODWS ph

16 The effect of ph Extreme ph levels will produce denaturation The structure of the enzyme is changed The active site is distorted and the substrate molecules will no longer fit in it At ph values slightly different from the enzyme s optimum value, small changes in the charges of the enzyme and it s substrate molecules will occur This change in ionisation will affect the binding of the substrate with the active site Paul Billiet ODWS

17 The effect of temperature Q10 (the temperature coefficient) = the increase in reaction rate with a 10 C rise in temperature. For chemical reactions the Q10 = 2 to 3 (the rate of the reaction doubles or triples with every 10 C rise in temperature) Enzyme-controlled reactions follow this rule as they are chemical reactions BUT at high temperatures proteins denature The optimum temperature for an enzyme controlled reaction will be a balance between the Q10 and denaturation Paul Billiet ODWS

18 The effect of temperature Enzyme activity Q10 Denaturation Temperature / C 2007 Paul Billiet ODWS

19 The effect of temperature For most enzymes the optimum temperature is about 30 C Many are a lot lower, cold water fish will die at 30 C because their enzymes denature A few bacteria have enzymes that can withstand very high temperatures up to 100 C Most enzymes however are fully denatured at 70 C 2007 Paul Billiet ODWS

20 20 2. Cofactors and Coenzymes Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes needed for proper enzymatic activity. Example: Iron must be present in the quaternary structure - hemoglobin in order for it to pick up oxygen.

21 21 Two examples of Enzyme Inhibitors a. Competitive inhibitors: are chemicals that resemble an enzyme s normal substrate and compete with it for the active site. Substrate Competitive inhibitor Enzyme

22 22 Inhibitors b. Noncompetitive inhibitors: Inhibitors that do not enter the active site, but bind to another part of the enzyme causing the enzyme to change its shape, which in turn alters the active site. Substrate active site altered Enzyme Noncompetitive Inhibitor