enzymes

Question 1

what does amylase digest starch to

Answer 1

to maltose

Question 2

what’s a cofactor

Answer 2

a substance that has to be present to ensure that an enzyme catalysed reaction takes place at an appropriate rate. some cofactors such as prosthetic groups are part of the enzymes structure, and others (mineral ion cofactors or organic coenzymes) form temporary associations with the enzyme

Question 3

are inorganic molecule or ion cofactors used up

Answer 3

no, they dont participate in the reaction

Question 4

what do cofactors help do

Answer 4

help the enzyme substrate bind together

Question 5

example of a cofactor (inorganic ion)

Answer 5

Cl- (cofactors for the enzyme amylase)

Question 6

what’s a prosthetic group in relation to an enzyme

Answer 6

a prosthetic group is where the cofactor is part of the enzymes structure

Question 7

an example of a prosthetic group

Answer 7

Zinc ions (Zn^2+)

Question 8

what is the prosthetic group Zn^2+ for

Answer 8

for carbonic anhydrase which catalyses the production of carbonic acid and Co2.

Question 9

whats a coenzyme

Answer 9

a small organic non-protein molecule that binds temporarily to the active site.
- they are changed in reactions and recycled continuously

Question 10

when is the enzyme-substrate complex formed

Answer 10

when a substrate molecule successfully collides with an enzyme molecule

Question 11

explain the induced fit theory

Answer 11

when the substrate molecules fit into the enzymes active site, the active site changes its shape slightly to mould itself around the substrate molecule.
( subtle changes in R group allow for this)

Question 12

what bonds bind the substrate to the active site

Answer 12

via hydrogen bonds, ionic attractions van der walls forces and hydrophobic interactions

Question 13

what do enzymes do to the activation energy of a reaction

Answer 13

lower the activation energy thus speeding up the reaction

Question 14

what are the 4 things affecting enzyme activity

Answer 14

temperature
pH
conc of substrate
conc of enzymes

Question 15

how does temp cause enzymes to denature

Answer 15

• weak bonds incl hydrogen bonds and ionic bonds break that hold the tertiary structure of the enzymes active site together
• active site shape changes, substrates can no longer fit well
• at high temp, irreversible changes occur to tertiary structure thus enzyme denatured

Question 16

what bonds allow for enzymes to be stable

Answer 16

more disulphide bonds

Question 17

why does increasing rate of reaction beyond optimum temp reduce rate of reaction

Answer 17

due to breaking of bonds holding the active sites tertiary structure

Question 18

how do u calc Q10

Answer 18

Q10= rate of reaction at T+10/ rate of reaction at T

Question 19

Q10 is aprox at 2 what does this mean

Answer 19

for every 10 degree rise in temp, the rate of reaction is doubled

Question 20

what happens if an enzyme is above or below optimum pH conditions

Answer 20

the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure

Question 21

how does enzyme conc affect rate of reaction

Answer 21

the more enzyme molecules there are in a solution, the more likely a substrate molecule will collide with an enzyme to form enzyme substrate complex- rate of reaction is increased
-if the amount of substrate is limited it comes to a point where theres more than enough enzyme molecules do deal with available substrate so adding more enzyme has no further affect

Question 22

how dos substrate conc affect rate of reaction

Answer 22

the higher the substrate conc the faster the reaction, more substrate molecules- a collision more likely to occur thus more active sites used- this is up to the saturation point ( adding more substrate molecules would make no diff ass all active sites full)

• substrate conc = limiting factor, as it increases so does rate up to a certain point
• -substrate conc decreases after time unless more substrate is added so rate will decrease over time , this makes the initial rate the highest rate of reaction

Question 23

simple: what are cofactors

Answer 23

non-protein substances

Question 24

some cofactors are inorganic molecules or ions, what does this help

Answer 24

they help the enzyme substrate bind together -they dont take part in the reaction so are not used up or changed

Question 25

give an example of a cofactor and what its a cofactor for

Answer 25

chloride ions are cofactors for the enzyme amylase

Question 26

what’s a prosthetic group

Answer 26

a cofactor that is tightly bound to the enzyme , its part of the enzyme .

Question 27

give an example of a prosthetic group

Answer 27

zinc ions (Zn^2+) are a prosthetic group for carbonic anhydrase, an enzyme in red blood cells which catalyses the production of carbonic acid from water and CO2.

Question 28

what are the two types of inhibitors

Answer 28

competitive and non competitive inhibitors

Question 29

what are competitive inhibitors and what do they do

Answer 29

• substances whose molecules have a simmilar shape to an enzymes substrate molecules.
• the competitive inhibitor fits into the active site so a substrate molecule cannot enter
• the amount of inhibition depends on the relative conc of a substrate and inhibitor molecules
• increasing the substrate conc dilutes the effect of the inhibitor

Question 30

what are non- competitive inhibitors and what do they do

Answer 30

• molecules that bind away from its active site (this site is the allosteric site).
• this causes the active site to change shape so the substrate molecules can no longer bind to it.
• they dont “compete” with the substrate molecules to bind with the active site as they are a different shape.
• increasing the conc of substrate wont make a difference to the reaction rate- enzyme activity will still be inhibited
• they disrupt the enzymes tertiary structure
• some non competitive inhibitors bind irreversibly to the active site and others dont.
• the max rate of reaction is reduced by non-competitive inhibitors

Question 31

what are metabolic pathways inhibited by

Answer 31

end product inhibition

Question 32

what is a metabolic pathway

Answer 32

a series of connected metabolic reactions. the product of the first reaction takes place with the second reaction- each reaction is catalysed by a different enzyme

Question 33

what is product inhibition

Answer 33

many enzymes are inhibited by the product of the reaction they catalyse

Question 34

what is end product inhibition

Answer 34

end product inhibition is when the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway- controls the amount of end product that gets made unsure=(non-competitive inhibition but reversible)

Question 35

both product and end product inhibition is reversible, what does this mean?

Answer 35

when the level of product starts to drop, the level of inhibition starts to fall so the enzyme can start to function= more product will be made

Question 36

what are 2 examples of medicinal drugs as enzyme inhibitors

Answer 36

• antiviral drugs

- some antibodies

Question 37

medicinal drugs as enzyme inhibitors: antiviral drugs (stop viruses like HIV)

Answer 37

-inhibits an enzyme which catalyses the replication of DNA , preventing viruses from replicating

Question 38

medicinal drugs as enzyme inhibitors: antibodies

Answer 38

e.g penicillin inhibits an enzyme which catalyses the formation of proteins in bacterial cell walls. This weakens the cell wall and prevents the bacterium from regulating osmotic* pressure . As a result the cell bursts and the bacterium is killed

Question 39

what do metabolic poisons do

Answer 39

they interfere with metabolic reactions causing damage, illness or death- theyre often enzyme inhibitors

Question 40

what does malonone* and arsenic inhibit

Answer 40

the enzyme catalysing respiration

Question 41

what is cyanide and what does it do

Answer 41

• highly toxic because it inhibits aerobic respiration and catalase
• KCN= toxic gas - when hydrolysed CN- ions bind irreversibly in mitochondria

Question 42

what is snake venom and what does it do

Answer 42

• inhibits enzyme that is important at gaps between neurones and muscles to break down the neurotransmitter.
• if this enzyme is inhibited, paralysis occurs as muscles contract.
• if muscles involved in breathing are paralysed, the suffocating occurs.