1.8

Question 1

what is measured in enzyme-catalysed reaction

Answer 1

1. the formation of the products of the reaction
2. the disappearance of the substrate

Question 2

4 effects of temperature on enzyme action

Answer 2

1. rise in temp increases kinetic energy of molecules
   they move around more rapidly and collide with each other more
2. more effective collisions results in more enzyme-substrate complexes being formed
3. rate of change slows at 45°C because hydrogen and other bonds in enzyme begin to break meaning substrate fits less easily
4. enzyme denatures(permanent changes shape) at around 60°C

Question 3

enzymes in human body optimum temp

Answer 3

40°C even though body temp is 37°C

Question 4

3 reasons human temp is 37°C and not 40°C in relation to enzymes

Answer 4

1. it would increase metabolic rate to be higher, but the advantage is offset by additional energy needed to maintain high temp(birds have 40°C because they have higher metabolic rate for high energy requirement of flight)
2. other proteins may denature at higher temp
3. at high temp, any further rise in temp perhaps due to illness may denature the enzyme

Question 5

pH

Answer 5

measure of hydrogen ion concentration
−log ([H+])

Question 6

2 effects of pH on enzyme action

Answer 6

1. alters charges on amino acids that make up active site so substrate can no longer become attached
2. acid may cause weak h and ionic bonds(between -NH2 and -COOH groups) maintaining the enzyme’s tertiary structure to break so the active site changes shape

Question 7

effect of enzyme concentration on rate or reaction

Answer 7

enzymes are free to be re-used after is has acted on its substrate

if there is an excess of substrates, an increase in enzymes increases the rate of the reaction, because more can be acted on at the same time

if the substrate is limiting, an increase in enzymes doesn’t increase the rate of the reaction, ad it will therefore stabilise at a constant level

Question 8

effect of substrate concentration on the rate of enzyme action

Answer 8

at low substrate conc, the enzymes have a limited number of substrates to collide with so active sites aren’t working to full capacity

if substrate conc is slowly increased, the rate of reaction increases in proportion

as more substrate is added till excess, the active sites gradually become filled until the working as fast as it can, so rate of reaction meets its maximum

Question 9

enzyme inhibitor

Answer 9

substances that directly/ indirectly interfere with the functioning of the active sire of an enzyme and so reduce its activity

Question 10

competitive inhibitor

Answer 10

have molecular shape similair to substrate
bind to and occupy the active site of enzyme
competes with substrate

Question 11

effect of competitive inhibitor conc on rate of reaction

Answer 11

if substrate conc is increased, the effect of the inhibitor is decreased- inhibitor is not permanently bound to the active site so substrate bonds when it leaves. At some point, all substrate molecules will occupy an active site

increased inhibitor conc means this process will take longer

Question 12

effect of non- competitive inhibitor conc on rate of reaction

Answer 12

enzyme can no longer function so increase in substrate conc doesn’t decrease effect of inhibitor

rate of reaction doesn’t reach maximum that non-competitive inhibitors and no inhibitors reach

Question 13

non-competitive inhibitor

Answer 13

attach themselves to enzyme at a binding site which is not the active site
they alter the shape of the enzyme and so the active site so substrates can no longer occupy it