topic 1 - factors affecting enzyme activity

Question 1

what are four factors that affect enzyme activity

Answer 1

temperature, pH, enzyme concentration, substrate concentration

Question 2

why does the rate of an enzyme controlled reaction increase when the temperature increases

Answer 2

when heat is increased, kinetic energy is also increased so molecules move faster - making enzymes more likely to collide with the substrate molecules - the energy of these collisions also increases meaning each collision is more likely to result in a reaction

Question 3

what happens to the enzyme’s molecules when the temperature rises

Answer 3

they vibrate more

Question 4

what happens when the temperature goes above a certain level

Answer 4

the vibration of the enzyme’s molecules breaks some of the bonds that hold the enzyme in shape - therefore the active site changes and the enzymes and substrate no longer fit together

Question 5

what does denatured mean

Answer 5

a protein that has lost its tertiary structure /its tertiary structure has been modified - it no longer functions as a catalyst

Question 6

what is the normal shape of a protein called

Answer 6

native conformation

Question 7

what is the reversal of denaturation called

Answer 7

renaturation

Question 8

what are human enzymes optimum temperature

Answer 8

around 37 C

Question 9

what are human enzymes optimum pH value

Answer 9

pH 7

Question 10

what is pepsins optimum pH value

Answer 10

pH 2

Question 11

what happens if the pH value is above or below the optimum

Answer 11

the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzyme’s tertiary structure in place - making the active site change shape so the enzyme is denatured

Question 12

why does an increased enzyme concentration increase the rate of reaction

Answer 12

the more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate complex - therefore increased concentration of enzyme increases the rate of reaction

Question 13

when does adding more enzymes have no further effect

Answer 13

when there’s more than enough enzyme molecules to deal with all the available substrate - if the amount of substrate is limited

Question 14

why does an increased saturation concentration increase the rate of reaction

Answer 14

the higher the substrate concentration, the faster the reaction - more substrate molecules means a collision between substrate and enzyme is more likely and so more active sites will be used

Question 15

why does substrate concentration only affect the rate of reaction up to a point

Answer 15

eventually there are so many substrate molecules that all the active sites are full - so adding more makes no difference

Question 16

what is the saturation point in enzymes

Answer 16

when all enzymes are occupied and are not searching for substrates

Question 17

why is the initial rate of reaction the highest rate of reaction

Answer 17

because substrate concentration decreases with time during a reaction so if no other variables are changed the rate of reaction will decrease over time too

Question 18

what can enzyme activity be prevented by

Answer 18

enzyme inhibitors

Question 19

what are enzyme inhibitors

Answer 19

molecules that bind to the enzyme that they inhibit

Question 20

what are the two types of inhibition

Answer 20

competitive inhibition and non competitive inhibition

Question 21

what do competitive inhibitor molecules have a similar shape to

Answer 21

substrate molecules

Question 22

what do competitive inhibitors compete with and what for

Answer 22

the substrate molecules to bind to the active site but no reaction takes place as they block the active site so no substrate molecules can fit in it

Question 23

what does how much the enzyme is inhibited depends on

Answer 23

the relative concentrations of the inhibitor and the substrate

Question 24

what happens if there’s a high concentration of the inhibitor

Answer 24

it will take up nearly all the active sites and hardly any of the substrate will get to the enzyme

Question 25

what happens if there’s a high concentration of the substrate

Answer 25

the substrate’s chances of getting to an active site before the inhibitor increase - so increasing the concentration of substrate will increase the rate of reaction

Question 26

what do non competitive inhibitor molecules bond to

Answer 26

the allosteric site

Question 27

what does the non competitive inhibitor do

Answer 27

it causes the active site to change shape so the substrate molecules can no longer bind to it

Question 28

why don’t non competitive inhibitors compete with the substrate molecules

Answer 28

because they are a different shape