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Cells & Enzymes Made of protein Present in all living cells Converts substrates into products Enzymes Biological catalysts Increase the rate of chemical reactions Remain unchanged by chemical reaction METABOLISM • This term really means two things: ANABOLISM and CATABOLISM ANABOLISM “ TO BUILD” molecules as in the biosynthesis of polymers.. We ingest food digest to monomers and THEN via ANABOLISM we make larger molecules Catabolism …then is to.. • “TO BREAK APART “ • Example: Glycogen, (starch) stored in the liver when needed for energy, is converted to glucose ( monomers). So during catabolism large molecules are broken into smaller molecules. Chemical Reactions A chemical reaction takes place when one or substances is chemically changed into one or more different substances. Chemical reactions take place in cells all the time. Catalyst Product Substrate Enzyme Hydrogen peroxide Manganese dioxide Water + oxygen Catalase Enzymes and Chemical Reactions Enzymes can speed reactions by lowering the amount of energy needed for a chemical reaction Catalysts A catalyst is a substance which speeds up a chemical reaction, without itself being changed by the reaction. 1. When a catalyst is present, less energy is needed to get the chemical reaction started. 2. When a catalyst is present, the speed of the chemical reaction is faster. 3. Although a catalyst helps a chemical reaction to happen, it is unchanged at the end of the reaction. Biological Catalysts The biological catalyst present in the cytoplasm of plant and animal cells that speeds up the breakdown of hydrogen peroxide is called CATALASE. Hydrogen peroxide REACTANTS catalase enzyme Oxygen + water PRODUCTS 2.2 Nature of Enzymes The biological catalyst present in the cytoplasm of plant and animal cells that speeds up the breakdown of hydrogen peroxide is called CATALASE. Hydrogen peroxide Catalase Water + oxygen Catalase cannot speed up any other reaction. It is SPECIFIC to this reaction. One Enzyme – One Reaction There are thousands of different enzymes in your body. Why are there so many different enzymes? Each enzyme has its own unique protein structure and shape, which is designed to match or COMPLEMENT its substrate. Lock & Key Hypothesis An enzyme only acts on one type of substance, or substrate. Therefore, the enzyme is said to be SPECIFIC to its one substrate. The shape of the active site (binding site) of the enzyme, matches the shape of the substrate. Allowing the two molecules to bind during the chemical reaction. This theory of enzyme action is called the ‘lock-and-key’ hypothesis. MOVIE Different enzymes for different jobs Enzymes involved in breakdown reactions Enzyme and substrate separate Enzyme-substrate complex Enzyme and products separate Enzymes involved in synthesis reactions Enzyme and substrates separate Enzyme-substrates complex Enzyme and product separate 2.3 Using a Control Why is it necessary to include a control experiment in an investigation? A control is an experiment that allows a comparison within an investigation in order to ensure that the conclusions drawn from the results are valid. Enzymes involved in breakdown reactions Hydrogen peroxide Starch Fat Protein Catalase Amylase Lipase Pepsin Water + Oxygen Maltose Fatty acids + Glycerol Amino acids 2.5 Effect of High Temperature • Optimum conditions are the conditions at which an enzymes works best • Rate of reactions may be affected by temperature and pH Notes on Denaturation Notes on Optimum temp 2.5 Effect of High Temperature What happens to the activity of an enzyme at high temperatures? Notes on Denaturation Notes on Optimum temp Effect of pH on enzymes When the pH changes outwith optimal conditions, the shape of the active site of the enzyme alters and the enzyme is Movie denatured. Effect of pH on enzyme activity Most enzymes work best at a pH close to neutral (pH7), but there are some exceptions. Pepsin, an enzyme found in the stomach, has an optimum pH of 2. Enzyme Summary Enzyme Substrate Product(s) Degradation or synthesis? Amylase Starch Maltose Catalase Hydrogen peroxide Protein Oxygen and water Amino acids Glucose-1phosphate Fat Starch Pepsin Phosphorylase Lipase Fatty acids s
