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33 Cards in this Set
- Front
- Back
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What is metabolism? |
~ A series of enzyme controlled reactions |
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What is a catabolic reaction? |
~ Enzymes that catalyse reactions that breakdown compounds
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What is a anabolic reaction? |
~ Enzymes that catalyse the build up of new products |
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What type of structure do enzymes have? |
~ They are globular proteins ~ They have a tertiary structure ~ Folded to give a 3D shape |
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How do substrates and enzymes bind? |
~ Substrate binds to part of the enzyme called the active site ~ The active site and the substrate are complimentary in shape ~ Enzymes are specific - only one substrate may enter each active site |
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Why are enzymes called catalysts? |
~ They speed up reactions ~Unchanged at the end of the reaction |
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Why are enzymes biological catalysts? |
~ They are proteins produced by cells ~ They act INTRACELLULAR & EXTRACELLULAR |
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How do enzymes work? |
~ By lowering the ACTIVATION ENERGY of a reaction |
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What causes enzymes and substrates to move around? |
~ Kinetic energy |
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What occurs when an enzyme and substrate collide successfully? |
~ The substrate will enter the enzymes active site ~ Enzyme-substrate complex will be formed ~ Activation energy is lowered = reaction is complete |
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What is the process of the lock & key theory? |
~ The substrate enters the active site to form an enzyme-substrate complex ~ Products form and are released from the active site ~ The enzyme is unchanged and can catalyse another reaction |
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What is the process of the induced fit theory? |
~ The enzyme active site is not FULLY complementary to the subtrate ~ As the substrate enters the active site... the active site changes shape ~ So that the active site becomes FULLY complementary to the substrate's shape ~ The changes in shape of both active site and substrate bring reactive groups close to each other ~ Weakining bonds in the substrate so the reaction takes place at a lower activation energy |
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What is an example of the induced fit theory? |
~ Lysozyme ~ Found in tears and saliva which damages bacterial cell walls |
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Description of enzyme action on TEMPERATURE? |
~ As temperature increases so does rate of reaction ~ Up to an optimum temperature where the rate of reaction is greatest ~ Increasing temperature above this optimum causes a decrease in the rate of reaction |
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Explanation of enzyme action on LOW TEMPERATURE? |
~ At low temperature enzyme and substrate molecules have low kinetic energy and rate of reaction is low ~ As the temperature increases ( from 0 to 37) the rate of reaction increases ~ The enzyme and substrate molecules gain more kinetic energy and they move faster ~ This results in more successful collisions between the substrate and the (enzyme's) active site ~ Therefore more enzyme-substrate complexes are formed (per unit time) ~ Therefore more product is formed in a certain time period |
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Explanation of enzyme action on increase above optimum TEMPERATURE? |
~ A maximum rate of reaction is reached at the optimum temperature ~ As the temperatures increases above the optimum temperature the rate of reaction decreases ~ This is due to the enzyme denaturing: : The high temperature causes enzyme molecules to vibrate more which breaks the bonds that maintain the tertiary structure (the bonds between atoms in the R-groups) hydrogen bonds are the weakest and therefore break first : The tertiary structure is altered which changes the shape of the active site : The substrate is no longer complimentary to the active site and therefore no enzyme-substrate complexes are formed ~ Denaturing is irreversible
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Optimum temperature for: a) For most enzymes? b) For humans? c) For psycrophiles (e.g. arctic bacteria)? d) For thermophiles (e.g. bacteria living in hot springs)? |
a) 40-60 b) 37 c) 4 d) 80 |
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Description of enzyme action on PH? |
~ Maximum rate of reaction occurs at the enzymes optimum ph ~ Changes in ph away from the optimum oh will lower the rate of reaction |
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Explanation of enzyme action on PH? |
~ Slight changes in ph changes the charge of the active site - which alters its structure ~ This inactivation of the enzyme is reversible ~ At extreme ph values the ionic bonds maintaining the tertiary structure are broken ~ This (permanently) denatures the enzyme and changes the shape of the active site ~ So the substrate is no longer complimentary - no enzyme-substrate complexes form |
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Description of enzyme action on SUBSTRATE CONCENTRATION? |
~ As the substrate concentration increases the rate of reaction increases up to a point ~ Then remains constant (plateau) |
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Explanation of enzyme action on SUBSTRATE CONCENTRATION? |
~ Initially there are moer enzyme molecules than substrate molecules ~ Therefore the substrate concentration that is the limiting factor ~ If the substrate concentration increases then so does the rate of reaction ~ The graph levels off and the rate becomes constant when there is excess substrate ~ The enzyme concentration is now the limiting factor as all the enzyme's active sites are occupied at any one time |
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Description of enzyme action on ENZYME CONCENTRATION? |
~ As the enzyme concentration increases the (initial) rate of reaction increases up to a point ~ ~ Then remains constant (plateau) |
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Explanation of enzyme action on ENZYME CONCENTRATION? |
~ Initially there are more substrate molecules than enzyme molecules ~ Therefore the enzyme concentration is the limiting factor ~ If the enzyme concentration increases then so does the rate of reaction ~ The graph levels off and the rate becomes constant when there are excess enzymes molecules ~ The substrate concentration is now the limiting factor ~ No more product can be formed |
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What investigative controls are there for enzyme experiment? |
~ A buffer solution should be added to the reactants to prevent ph from varying
~ A repeat with enzyme boiled in solution and then cooled should be carried to show that it is the enzymes that are catalysing the reaction and not another factor |
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What is an inhibitor? |
~ Molecules that can reduce the ability of an enzyme to speed up a reaction |
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What is a competitive inhibitor? |
~Have similar shape to the substrate molecule ~ They are complementary in shape to the enzyme's active site ~ They fit into the active site and prevent the substrate molecule from doing so ~ The rate of reaction slows down |
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What is a non-competitive inhibitor? |
~ Do not have a similar shape to the substrate ~ They bind to another site on the enzyme (the allosteric site) which alters its tertiary structure and the active site changes shape ~The substrate cannot fit in the active site |
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What is the effect of substrate concentration on inhibition? |
~ If the concentration of the substrate is increased with a competitive inhibitor the inhibitor is overcome ~ Increasing the substrate concentration with a non-competitive inhibitor will have no effect on the level of inhibition |
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Where are enzymes normally used? |
~ Used in a number of industrial processes as biological catalysts ~ E.g. in the production of high-fructose corn syrups from corn starch |
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How can the use of enzymes be improved? |
~ By immobilising them onto an inert matrix which increases their stability ~ They are fixed onto a gel membrane or embedded into alginate beads |
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What are the advantages of using immobilised enzymes? |
1) They are more stable so can withstand higher temperatures and a wider range of pH 2) The enzymes stay in one place so the product is not contaminated and does not need purifying 3) The enzymes are easily recovered for reuse 4) A continuous process is possible |
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What are disadvantages of using immobilised enzymes? |
~ The immobilised process may cause loss of activity in the enzyme ~ Development of successful immobilised methods is expensive |
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Where can immobilised enzymes be used has diagnostic tools? |
~ Used has biosensorss ~ The enzyme allows for the detection of a specific molecule in a mixed solution. ~ E.g. biosensors can be used for the diagnosis and monitoring of diabetes by quantifying the levels of glucose in the blood |
