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Enzymes: “Helper” Protein molecules AP Biology 5/23/2017 Nothing works without enzymes! How important are enzymes? all chemical reactions in living organisms require enzymes to work building molecules synthesis enzymes enzyme + breaking down molecules digestive enzymes We can’t live without enzymes! enzymes speed up reactions “catalysts” AP Biology enzyme + Examples synthesis + enzyme digestion enzyme AP Biology + Enzymes are proteins Each enzyme is the specific helper to a specific reaction each enzyme needs to be the right shape for the job enzymes are named for the reaction they help Oh, I get it! They end in -ase sucrase breaks down sucrose proteases breakdown proteins lipases breakdown lipids DNA polymerase builds DNA AP Biology Enzymes aren’t used up Enzymes are not changed by the reaction used only temporarily re-used again for the same reaction with other molecules very little enzyme needed to help in many reactions substrate active site AP Biology product enzyme It’s shape that matters! Lock & Key model shape of protein allows enzyme & substrate to fit specific enzyme for each specific reaction AP Biology 2 1 3 AP Biology Enzyme vocabulary Enzyme helper protein molecule Substrate molecule that enzymes work on Products what the enzyme helps produce from the reaction Active site AP Biology part of enzyme that substrate molecule fits into What affects enzyme action Correct protein structure correct order of amino acids why? enzyme has to be right shape Temperature why? enzyme has to be right shape pH (acids & bases) AP Biology why? enzyme has to be right shape Order of amino acids Wrong order = wrong shape = can’t do its job! chain of amino acids DNA folded protein right shape! folded protein chain of amino acids DNA AP Biology wrong shape! Temperature Effect on rates of enzyme activity Optimum temperature greatest number of collisions between enzyme & substrate human enzymes 35°- 40°C (body temp = 37°C) Raise temperature (boiling) denature protein = unfold = lose shape Lower temperature T° molecules move slower fewer collisions between enzyme & AP Biology substrate Temperature reaction rate human enzymes 37° temperature AP Biology What’s happening here?! How do cold-blooded creatures do it? AP Biology pH Effect on rates of enzyme activity changes in pH changes protein shape most human enzymes = pH 6-8 depends on where in body pepsin (stomach) = pH 3 trypsin (small intestines) = pH 8 AP Biology pH intestines trypsin What’s happening here?! reaction rate stomach pepsin 0 1 2 3 4 5 6 pH AP Biology 7 8 9 10 11 12 13 14 INDUCED FIT: ENZYME FITS SNUGLY AROUND SUBSTRATE -- “CLASPING HANDSHAKE” COFACTORS Cofactors are nonprotein enzyme helpers such as minerals (eg. Zn, Fe, Cu) Coenzymes are organic cofactors (eg. vitamins) Enzyme Inhibitors Competitive inhibitor: binds to the active site of an enzyme, competes with substrate Noncompetitive inhibitor: binds to another part of an enzyme enzyme changes shape active site is nonfunctional INHIBITION OF ENZYME ACTIVITY REGULATION OF ENZYME ACTIVITY To regulate metabolic pathways, the cell switches on/off the genes that encode specific enzymes Allosteric regulation: protein’s function at one site is affected by binding of a regulatory molecule to a separate site (allosteric site) Activator – stabilizes active site Inhibitor – stabilizes inactive form Cooperativity – one substrate triggers shape change in other active sites increase catalytic activity FEEDBACK INHIBITION End product of a metabolic pathway shuts down pathway by binding to the allosteric site of an enzyme Prevent wasting chemical resources, increase efficiency of cell FEEDBACK INHIBITION For enzymes… What matters? SHAPE! AP Biology 5/23/2017