Enzymes

Question 1

give an example of an extracellular enzyme

Answer 1

amylase, secreted by mouth cells and catalyses hydrolysis of starch

Question 2

give an example of an intracellular enzyme

Answer 2

catalyses, breaks down hydrogen peroxide

Question 3

what type of proteins are enzymes

Answer 3

globular

Question 4

what is the active site

Answer 4

the part of the enzyme where the substrate molecules bind

Question 5

the active site shape is determined by what

Answer 5

tertiary structure

Question 6

what is it called when a substrate binds to an active site

Answer 6

enzyme-substrate complex

Question 7

how do enzymes speed up reactions

Answer 7

reduce the activation energy

Question 8

what are the two reasons for why the formation of an enzyme-substrate complex lowers activation energy

Answer 8

-if two substrates need to be joined, attaching to the enzyme holds them close together so there is less repulsion and can bond more easily
- in a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate so it can break down more easily

Question 9

describe the lock and key model

Answer 9

the idea that the substrate fits into the enzyme as they have the exact complementary shape

Question 10

describe the induced fit model

Answer 10

the substrate has to have the right shape to bind to the active site but also has to change the shape of the active site

Question 11

how does temperature affect enzyme activity

Answer 11

if temperature is too high, molecules vibrate more causing to break bonds that hold enzyme shape and the active site will change shape and become denatured
if temperature is too low then the number of successful collisions will reduce due to lack of kinetic energy

Question 12

what is the temperature at which the rate of an enzyme controlled reaction is at its fastest

Answer 12

optimum temperature

Question 13

what is the equation for temperature coefficient

Answer 13

Q10= R2 (rate at higher temperature)/ R1 (rate at lower temperature

Question 14

How does pH affect enzyme activity

Answer 14

the H+ ions and OH- ions produced above and below optimum pH, can break the ionic bonds in the tertiary structure, causing Mayme to denature

Question 15

what enzyme works best at pH two and is found in stomach

Answer 15

pepsin

Question 16

how does enzyme conc affect enzyme activity

Answer 16

the more enzyme molecules in a solution the more likely there is for a collision to occur with a substrate molecule
however if substrate is limited there comes a point where adding further enzyme has no further affect

Question 17

what is the effect of substrate conc on enzyme activity

Answer 17

the higher the substrate conc, the faster the reaction, more likely for collisions to occur, only true up to a saturation point where enzyme conc becomes the limiting factor
substrate conc also decreases over tike during a reaction so if no other substrate is added then the speed of reaction will also decrease over time

Question 18

what is a cofactor

Answer 18

a non protein substance that binds to an enzyme to help it function

Question 19

what is an inorganic cofactor

Answer 19

help substrate and enzyme bind but don’t participate directly so aren’t used up or changed in any way

Question 20

what are organic cofactors called and how do they aid enzyme function

Answer 20

coenzymes, participate in reaction and often act as carriers by moving chemical groups between different enzymes

Question 21

what are competitive inhibitors

Answer 21

molecules that have the same shape as substrate molecules, block active site so substrate cannot bind, high conc of inhibitor means most active sits will be take up, however if there is a higher conc of substrate than the chance of it reaching an active site before the inhibitor is high

Question 22

what are non-competitive inhibitors

Answer 22

bind to enzyme away from the active site and to the allosteric site, changing active site shape so substrate molecules can no longer bind

Question 23

what type of drugs act as enzyme inhibitors

Answer 23

antiviral drugs, prevent replication of DNA
antibiotics

Question 24

what metabolic potions act as enzyme inhibitors

Answer 24

cyanide- non competitive, irreversible
malonate- competitive
arsenic- non competitive

Question 25

what is a prosthetic group and give an example

Answer 25

a cofactor tightly bound to an enzyme- Zn2+ for carbonic anhydrase

Question 26

what nutrition group is often a source of coenzymes

Answer 26

vitamins

Question 27

what is the cofactor for amylase

Answer 27

chloride ion

Question 28

what is end product inhibitor and what do they regulate

Answer 28

metabolic pathways are regulated by end-product inhibition, a metabolic pathway isa series of metabolic reactions, the product of the first takes part in the second reaction and so on, each reaction uses a different enzyme, many enzymes are inhibited by the product of the reaction they catalyse, the final product in the metabolic pathway inhibits an enzyme that acts easier on in the pathway