Enzymes

Question 1

what are enzymes

Answer 1

are biological catalysts that increase the rate of reaction by lowering the activation energy. they are not used up in the process

Question 2

normally what type of protein are enzymes

Answer 2

globular

Question 3

what is a intracellular enzyme

Answer 3

enzymes that work inside the cell
eg catalase, breaks down hydrogen peroxide

Question 4

what are extracellular enzymes

Answer 4

enzymes that work outside the cell
eg amylase, catalyses hydrolysis of starch

Question 5

explain the lock and key hypothesis

Answer 5

• like a lock and key, only a specific substrate will fit the active site of an enzyme.
• when the substrate is bound, an enzyme-substrate complex is formed.
• the substrates then react and the products are formed in an enzyme-product complex

Question 6

what is an active site

Answer 6

an area within the tertiary structure of the enzyme that has a shape that is complementary to the shape of a specific substrate molecule.

Question 7

explain the induced fit hypothesis

Answer 7

• some evidence suggests that the active site changes shape slightly as the substrate enters
• when the enzyme-substrate complex occurs, due to the enzyme moulding around the substrate, it puts strain on the bonds and lowers the activation energy needed to break them
• when the products are removed the active site returns to its original shape

Question 8

what are the factors the affect enzyme activity

Answer 8

1- temperature
2- pH
3- enzyme concentration
4- substrate concentration

Question 9

explain denaturation of enzymes at high temp

Answer 9

• at higher temps, the bonds holding the protein’s tertiary structure, vibrate more
• as temp increases further the bonds vibrations increase until the bonds strain and break
• breaking these bonds results changes in the enzymes tertiary structure, thereofre the active site is no longer complementary

Question 10

what is an enzymes optimum temp

Answer 10

this is a temperature at which the enzyme has the highest rate of activity.
many enzymes in the human body have an optimum around 37*C

Question 11

how does pH affect enzyme activity

Answer 11

the active site will only be in the right shape at a certain hydrogen ion concentration, this is the optimum pH
when it changes from the optimum, more acidic or alkaline, the structure of the enzyme is altered, changing the shape of the active site

Question 12

explain how changing the concentration of substrate increase enzyme activity

Answer 12

when concentration of substrate is increased, the number of substrate molecules in a particular area/volume increases.
the increased number of substrate particles leads to a high collision rate with active site of enzymes and the formation of more enzyme-substrate complexes

Question 13

what is Vmax

Answer 13

it is the maximum rate of reaction, at this point all the active sites are occupied by substrate particles and no more enzyme-substrate complexes can be formed until products are released from active sites. the only way to increase the rate of reaction would be to add more enzyme or increase the temperature

Question 13

explain how increasing enzyme concentration increases enzyme activity

Answer 13

increasing concentration of enzymes, increases the number of available active sites in a particular area/volume, leading to the formation of enzyme-substrate complexes at a faster rate.

Question 14

what types of enzyme inhibitors are there

Answer 14

competitive and non-competitive

Question 15

how do competitive inhibitors work

Answer 15

• they have similar shape to substrate molecules
• they compete with the substrate molecules to bind the active site, but no reaction takes place
• this blocks the active site so the enzyme cant carry out its function

Question 16

competitive inhibitors affect on rate of reaction?

Answer 16

• reduces rate of reaction for a given concentration of substrate, does not change Vmax
• substrate concentration is increased enough there will be chance of substrate reaching the active site before the inhibitor, so rate of reaction will increase

Question 17

how do non-competitive inhibitors work

Answer 17

• bind to the enzyme allosteric site (location other than the active site)
• binding alters the enzymes tertiary structure, meaning active site changes shape

Question 18

non-competitive inhibitors affect on rate of reaction

Answer 18

increasing the concentration of enzyme or substrate will not overcome the effect of a non-competitive inhibitor.
increasing the concentration of the inhibitor will decrease the rate of reaction further as more active sites are changed.

Question 19

why would an inhibitor binding be reversible

Answer 19

if the bonds between the enzyme and inhibitor are weaker hydrogen bonds or weak ionic bonds, they can easily be overcome. so the inhibitor can be removed

Question 20

what is a cofactor?

Answer 20

is a inorganic non-protein compound required to carry out enzyme’s function as a biological catalysts

Question 20

why would an inhibitor binding be irreversible

Answer 20

the bonds between the enzyme and inhibitor are strong covalent bonds, the bonds cant be easily overcome so the inhibitor cannot be easily removed

Question 21

what is end-product inhibition

Answer 21

it is when the end product in a metabolic pathway inhibits the enzyme that produces it
it regulates the pathway and controls the amount of end-product that gets made.

Question 22

what is a coenzyme?

Answer 22

are organic cofactors which do not bind permanently, they facilitate the binding of substrate to enzyme.
many are derived from vitamins

Question 23

what is a precursor enzyme

Answer 23

they are enzymes in an inactive form, they often need to undergo a change in shape (tertiary structure) to be activated

Question 24

what is a cofactor acitvator?

Answer 24

they are inorganic metal ions which temporarily binds to the enzyme and alters the active site, making the reaction more feasible

Question 25

what are prosthetic groups

Answer 25

these are cofactors that are permanently bound to the enzyme. in haemoglobin, the haem group containing iron is permanently bound to the enzyme, which serves as a means of binding oxygen.