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Enzymes (Keywords (Active site: Indent on the surface of an enzyme with a…
Enzymes
Keywords
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Catalyst: Chemical that speeds up the rate of a reaction and remains unchanged/reusable at the end of the reaction
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Cofactor: Substance that has to be present to ensure enzyme-catalysed reactions occur at the right rate
Enzyme-substrate complex: Complex formed by temporary binding of enzyme and substrate during an enzyme-catalysed reaction
Prosthetic group: Cofactor that is permanently bound, by covalent bonds, to an enzyme molecule
Co-enzymes: Non-protein cofactors that bind temporarily to the active site of the enzyme either just before or at the same time as the substrate, but are chemically changed during the reaction
Enzyme-product complex: Enzyme molecule with product molecules in its active site, joined temporarily by non-covalent forces
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Non-competitive inhibition: Changes the shape of the active site, stopping ES complexes from forming
Temperature
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Rate of ES complexes increases, rate of reaction increases up to a point
May break some weak bonds, such as the hydrogen and ionic bonds that hold the tertiary structure of the active site
As the active site changes shape, it is no longer complementary to the substrate
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Catalase
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In eurkaryotes, it is found inside peroxisomes
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Active site
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Shape of the active site can be altered by changes in temperature or pH as these affect the bonds that hold proteins in their tertiary structure
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Cofactors
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Co-enzymes
Small, organic, non-protein cofactors
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Enzyme degredation
Cells continuously degrade old enzyme molecules to their component amino acids and synthesising enzyme molecules from amino acids
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pH
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Excess hydrogen ions will interfere with the hydrogen/ionic bonds so the active site will change shape, decreasing the rate of reaction
Will also alter the charges on the active site as more protons will cluster around negatively charged groups on the active site
Inhibitors
Competitive
Compete directly with substrate molecules, forming an enzyme-inhibitor complex
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Non-competitive
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Some are reversible, some irreversible
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Lock & Key: Tertiary structure of the enzyme's active site is complementary to the substrate molecule
Substrate molecule fits into the enzyme's active site and temporarily forms hydrogen bonds, holding the two together
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Bonds form between substrate molecules, forming an enzyme-product complex
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Induced Fit
Presence of the substrate molecule in the enzyme's active site induces a shape change, making the shapes more complementary/precise
Concentration
Substrate
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As it is increased further the rate will no longer increase as substrate concentration is no longer the limiting factor