2.1.4 enzymes

Question 1

what are enzymes

Answer 1

enzymes act as biological catalysts to speed up metabolic reactions

Question 2

what is an intracellular enzyme

Answer 2

an enzyme that works inside the cell

Question 3

what is an example of an intracellular enzyme

Answer 3

catalase which breaks down toxic hydrogen peroxide into oxygen and water

Question 4

what is an extracellular enzyme

Answer 4

an enzyme that works outside of cells

Question 5

what is an example of an extracellular enzyme

Answer 5

amylase and trypsin
they are both used in digestion. amylase breaks down starch into maltose. trypsin hydrolyse peptide bonds turning long polypeptides into smaller ones.

Question 6

what kind of protein are enzymes

Answer 6

globular proteins

Question 7

how does an enzyme speed up rate of reaction

Answer 7

it lowers the activation energy so more particles are able to collide with enough energy to react

Question 8

what is the active site of an enzyme

Answer 8

the part of the enzyme that the substrate molecules bind to. it has a specific shape.

Question 9

what is the lock and key model

Answer 9

the substrate fits into the active site like a key in a lock to form an enzyme-substrate complex

Question 10

what is the induced fit model

Answer 10

as the substrate binds to the active site, the active site changes shape slightly to fit the substrate more closely.

Question 11

how does temperature effect enzyme activity

Answer 11

rate of an enzyme controlled reaction increases with temperature as the molecules have more kinetic energy so collisions are more frequent an have more energy
if temperature is too high enzymes denature as some bonds break and change the shape of the active site

Question 12

what does the temperature coefficient show

Answer 12

it shows how the rate changes with temperature

Question 13

what is the temperature coefficient (Q10)

Answer 13

Q10 = r2 (rate at higher temperature)/ r1(rate at lower temperature)

Question 14

how does pH effect enzyme activity

Answer 14

all enzymes have an optimum pH value. above and below this the H+ and OH- ions can mess up the ionic bonds and hydrogen bonds in the tertiary structure so the enzyme denatures.

Question 15

how does enzyme concentration effect enzyme activity

Answer 15

increasing enzyme concentration increases rate of reaction because more enzyme substrate complexes can form.
substrate concentration can be limited so there is a point where further increasing the enzyme concentration has no effect on rate

Question 16

how does substrate concentration effect enzyme activity

Answer 16

the higher the substrate concentration the more likely a collision between enzyme and substrate is which means rate of reaction is increased
this is until a saturation point where all the active sites are full
substrate concentration decreases as the reaction goes on so rate of reaction will decrease over time.

Question 17

how can we measure rate of an enzyme controlled reaction

Answer 17

• measure how fast the product is formed
• measure how fast the substrate is used up

Question 18

what are cofactors

Answer 18

non protein substances that bond to enzymes to help them work

Question 19

how do some inorganic ions work as cofactors

Answer 19

they help the enzyme and substrate bind together. they are not used up or changed in the reaction

Question 20

what are organic molecule cofactors called

Answer 20

coenzymes

Question 21

how do coenzymes work

Answer 21

they participate in the reaction and are changed by it. they often work as carrier molecules and are continuously recycled in this process

Question 22

what is a tightly bound cofactor to the enzyme called

Answer 22

prosthetic group

Question 23

what is competitive inhibition

Answer 23

when a similar shaped molecule to the substrate binds to the active site of an enzyme blocking it from the substrate.

Question 24

what is non competitive inhibition

Answer 24

when a non competitive inhibitor binds to the allosteric site. this changes the shape of the active site so the substrate cant fit.

Question 25

what make an inhibition irreversible

Answer 25

strong covalent bonds between enzyme and inhibitor

Question 26

what makes the inhibition reversible

Answer 26

weak ionic or hydrogen bonds between the enzyme and inhibitor

Question 27

how are some drugs enzyme inhibitors

Answer 27

• antiviral drugs can stop viruses replicating by inhibiting reverse transcriptase
• some antibiotics inhibit transpeptidase which stops the formation of proteins for the bacterial cell wall. this weakens the cell wall the cell bursts

Question 28

how are some poisons inhibitors

Answer 28

cyanide, malonate, and arsenic all inhibit enzymes in respiratory reactions which causes cells to die.

Question 29

what is product inhibition

Answer 29

when the product of a reaction inhibits the enzyme involved in the reaction

Question 30

what is end product inhibition

Answer 30

when the end product of a metabolic pathway inhibits an enzyme that acts earlier on in the pathway

Question 31

what is end product inhibition useful for

Answer 31

regulation metabolic pathways

Question 32

how can enzyme inhibition be used to protect cells

Answer 32

enzymes can be synthesised as inactive precursors which are activated once the part of the precursor molecule is removed.
e.g. some proteases are made like this so they don’t damage proteins inside the cell