T1 3 Enzymes (Temp)

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Effect of temperature on enzyme activity (Points covered during class)
  Enzymes: Revision Notes Factors affecting rate of enzyme reactions: 1. Temperature2. pH3. Enzyme Concentration4. Substrate Concentration How temperature affects rate of enzyme activity: ã Rate of enzyme activity depends on kinetic energy (K.E.) of molecules:  1. Rise in temperature2. Rise in kinetic energy of molecules3. Rise in collisions between enzymes and substrate molecules4. Increase chance of formation of enzyme substrate complex5. Increase in rate of reaction Enzyme Graphs: Page 11 ã Enzymes have an optimum working   temperature (Temp at which rate of enzyme activity is max) ã Different enzymes have different optimum temperatures. ã At low temperatures (<5 0 C), enzymes are inactive ã As temperature rises, rate of enzyme activity increases   ã Inactivation: Minimal enzyme activity ã Due to very low KE of substrate & enzyme molecules ã Not permanent ã As the temp increases beyond optimum temp, rate of enzyme activity drops ã Enzyme is completely denatured by the extreme heat (>60 0 C), rate of enzyme activity comes to acomplete stop Denaturation ã Occurs when 3D protein structure changes its shape ã Results in the loss/changing of active sites ã No longer acts as a catalyst ã Caused by acids, alkalis and extreme heat (boiling) ã Irreversible   Enzyme Graphs: Things to remember  ã Note axes:  – X axis: Independent variable (Controlled by experimenter), OR Time  – Y axis: Dependent variable (Measured) ã Must always use DATA in answer (Read from graph!) ã Gradient of graphs: Y/X  Enzyme Graphs: Pg 12  – Gradient: Product formed/Time (Rate of reaction)  – Steeper = Faster rate of reaction ã 2 parts of graph:  – Accumulation of product (+ve gradient)  – When reaction stops (gradient = 0, no more product formed) ã When reaction starts (+ve gradient):  – Rate of reaction fastest for A (most product formed in the same amount of time), followed byB, then C  – Fastest for A due to highest temperature (60 0 C), followed by B (37 0 C), then C (25 0 C).  – The higher the temperature, the higher the KE  – More collisions between substrate and enzymes  – Increase chance of formation of enzyme-substrate complex  – Reaction rate is faster  ã When reaction stops (gradient = 0):  – No more product is formed after a short period of time (~5 min) for A, as the high temperature (60 0 C)causes enzymes to denature  – Enzymes no longer catalyse the reaction, and the reaction stops  – Not all substrate used up, amount of product formed is lower than in B.  – No more product is formed after a period of time (~20 min) for B, as the reaction reaches end point(all substrate used up)  – Max amt of product formed, more product is formed at 37 0 C compared to reaction at 60 0 C  – Reaction at 25 0 C (Graph C) is slower, has not reached end point  – Products are still being formed (+ve gradient), curve does not plateau
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