Enzymes

Question 1

define intracellular

Answer 1

within cells

Question 2

define extracellular

Answer 2

outside cels

Question 3

give an example of an intracellular enzyme

Answer 3

catalase - catalases the breakdown of hydrogen peroxide to harmless oxygen and water

Question 4

give two examples of extracellular enzymes

Answer 4

amylase - catalases hydrolysis of starch

trypsin - catalases hydrolysis of peptide bonds

Question 5

where is trypsin produced / secreted ?

Answer 5

pancreas / small intestine

Question 6

All enzymes are … proteins

Answer 6

globular proteins

Question 7

what happens when a substance binds to an enzyme ?

Answer 7

the enzyme-substrate complex is formed, which lowers the activation energy

Question 8

If the two substrates must join, what does the enzyme do?

Answer 8

holds them closer, reducing repulsion

Question 9

If an enzyme is catalysing a breakdown reaction…

Answer 9

fitting into the active site puts strain on the bonds (so breaks up more easily)

Question 10

explain what happens to enzyme when the temp goes to high

Answer 10

The enzyme’s molecule vibrates too much, breaking some of the bonds, changing the shape of the active site (denatured)

Question 11

what does the temperature coefficient (Q10) show?

Answer 11

how much the rate of reaction changes when the temp is raised by 10 ‘C

Question 12

explain how pH affects enzymes

Answer 12

the H+ and OH- ions interact and break the ionic bonds and H-bonds, changing the shape of the active site

Question 13

give two experiments used to measure rate of reaction

Answer 13

• breakdown of hydrogen peroxide (using catalase)

- breakdown of starch (using amylase)

Question 14

name the factors that may affect an enzyme reaction

Answer 14

temp / pH / enzyme conc / substrate conc

Question 15

what is a buffer ?

Answer 15

a solution able to resist changes in pH when small amounts of acid / alkali are added

Question 16

what is a cofactor?

Answer 16

a Substance that is Required by some Enzymes for them to work

Question 17

what is the cofactor of amylase ?

Answer 17

chloride ions

Question 18

how do inorganic cofactors help the enzyme ?

Answer 18

help enzyme and substrate bind together (not used up/changed)

Question 19

what are co enzymes ?

Answer 19

organic cofactors

Question 20

how do co enzymes help enzymes ?

Answer 20

act as carriers, by moving chemicals between enzymes (changed by reaction) - they are continually recycled

Question 21

what is a cofactor tightly bound to an enzyme known as ..?

Answer 21

prosthetic group

Question 22

what is the prosthetic group for carbonic anhydrase ?

Answer 22

zinc ions

Question 23

what are enzyme inhibitors ?

Answer 23

molecules that bind to enzymes and prevent them from performing their function (may be competitive/non-competitive)

Question 24

how do competitive inhibitors inhibit ?

Answer 24

• similar shape so fit active site
• compete with substrate to bind with enzyme
• block substrate molecule from binding

Question 25

Describe rate of reaction with competitive inhibitors

Answer 25

rate of reaction will increase as substrate concentration increases

Question 26

how do non-competitive inhibitors inhibit ?

Answer 26

• bind to allosteric site
• causes change in active site shape
• substrate no longer able to bind

Question 27

Describe rate of reaction with non-competitive inhibitors

Answer 27

increasing substrate concentration will have little effect on rate of reaction

Question 28

when are inhibitors reversible ?

Answer 28

weak hydrogen / ionic bonds between enzyme and inhibitor

Question 29

when are inhibitors irreversible ?

Answer 29

strong covalent bonds between enzyme and inhibitor

Question 30

Describe the role of reverse transcriptase inhibitors

Answer 30

inhibit the enzyme reverse transcriptase, which catalyses the replication of viral DNA

Question 31

how does penicillin work ?

Answer 31

• inhibits the enzyme transpeptidase, which catalyses formation of proteins in bacterial walls
• weakens cell wall and prevents regulation of osmotic pressure
• cell bursts (bacterium killed)

Question 32

how is cyanide dangerous ?

Answer 32

irreversible inhibitor of the enzyme cytochrome c oxidase, which catalyses respiration reactions

Question 33

how is malonate dangerous ?

Answer 33

inhibits enzyme succinate dehydrogenase (catalyses respiration reactions)

Question 34

how is arsenic dangerous ?

Answer 34

inhibits enzyme pyruvate dehydrogenase (catalyses respiration reactions)

Question 35

what is a metabolic pathway ?

Answer 35

series of connected metabolic reactions

Question 36

what is product inhibition ?

Answer 36

when the product inhibits the enzyme that catalyses the reaction (reversible)

Question 37

what is end-product inhibition ?

Answer 37

when the end product of the metabolic pathway inhibits enzyme at start (reversible)

Question 38

why are some enzymes synthesized as inactive precursors ?

Answer 38

prevent them from causing damage to cells

Question 39

define biological catalyst

Answer 39

a protein that speeds a metabolic reaction without getting used up / changed

Question 40

what to remember when describing graphs

Answer 40

describe steepness as well

Question 41

what is V max ?

Answer 41

max rate at which the enzyme catalyses a reaction

Question 42

what terms to remember to use with enzymes …

Answer 42

enzyme - substrate complex
complementary binding
specific

Question 43

what word is used to describe flat graph

Answer 43

plateau

Question 44

what is vitamin B12 required for ?

Answer 44

successful transfer of methyl groups

Question 45

what is vitamin B3 required for ?

Answer 45

acts a an antioxidant