enzymes

Question 1

do enzymes raise or lower energy of activation

Answer 1

lower

Question 2

function of isomerases

Answer 2

rearrange atoms

Question 3

function of ligase

Answer 3

use of ATP to combine molecules

Question 4

function of lyases

Answer 4

removal or add of atoms to or from double bond

Question 5

what are apoenzymes and holoenzymes

Answer 5

apoenzyme = inactive enzyme i.e withoutnon protein cofactor
holoenzyme = enzyme with its nonprotein cofactor

Question 6

give an example of cofactors

Answer 6

inorganic ions

Question 7

what features of the active site allows for reactions to occur faster

Answer 7

the shape and chemical enviroment

Question 8

how do enzymes bind to the substrate

Answer 8

via h bonds, salt bridges and hydrophobi interactions

Question 9

what are the three types of enzyme specificity

Answer 9

absolute - catalyse one type of reaction for a single substrate
group - catalyse one type of reaction for simialr substrates
linkage -catalyse one type of reaction for a specific bond

Question 10

what is the turnover number

Answer 10

number of molecules of substrate converted to product per enzyme molecule per second

Question 11

how are enzymes arranged in the cell

Answer 11

segregated in specific organelles so enzyme reactions do not complete other reactions

Question 12

what is an isoenzyme

Answer 12

different forms of enzymes that do the same reactions in different tissues

Question 13

what is free energy of activation

Answer 13

the energy barrier separating reactant and product

Question 14

what is the x and y intersecgt on the lineweaver-burk plot

Answer 14

y intersect = 1/Vmax
x intersect = -1/Km

Question 15

what is micheals constant

Answer 15

Km
where Km is the substrate conc at which the reaction velocity = 1/2Vmax

Question 16

what does a small Km or a Large Km mean

Answer 16

small = high substrate affinity
- low substrate needed to half saturate the enzyme to reach a velocity of 1/2Vmax
large = low substrate affinity
- high substrate level needed to half saturate the enzyme to reach a velocity of 1/2Vmax

Question 17

what are the factors affecting enzymes

Answer 17

substrate conc, pH, temperature, inhibitors, activaors, modulators

Question 18

what effect has pH on enzyme

Answer 18

denaturation, can affect the charges on the enzyme and substrate- influences binding

Question 19

what effect has temp on enzymes

Answer 19

denature at high temps, enzumes have an optimum temp but are fully denatured at 70 degreec c

Question 20

what are inhibitors

Answer 20

cause a loss of enzyme activity, three types:
- reversible
- irreversible
- allosteric

Question 21

what are the types of reversivle inhibitors

Answer 21

competitive, noncompetitive, uncompetitive

Question 22

what are the irreversible enzymes

Answer 22

active site directed or suicide inhibitor

Question 23

what is a reverse inhibitor

Answer 23

binds to enzyme via non covalent bonds (weak). they go on and off allowing the enzyme to lose and gain ability. inhibition effect is reversed by substrate conc increase

Question 24

what is an irreversible inhibitor

Answer 24

binds at or near the active site via covalent bonds. sometimes they can destroy a crucial functional group in the enzyme. enzyme activity is not regained by increasing S levels

Question 25

what is an allosteric inhibitor

Answer 25

they bind to a place other than the active site called the allosteric site

Question 26

what is competitive inhibition

Answer 26

type of reversible inhibition where an inhibitor binds at the active site to prevent substrate binding. increasing S can reverse the reaction

degree of inhibition can vary depending on affinities of the enzyme for substrate and inhibitor

Question 27

look at graph for competitive inhibition and know the labels

Question 28

what are examples of competitive inhibitors

Answer 28

statin drugs for cholesterol synthesis, malonate, 2-sulfa drugs

Question 29

what is a noncompetitive inhibitor

Answer 29

has a shape different to the substrate and binds to the allosteric site causing a change in the shape of the active site. adding more substrate does not reverse this reaction

Question 30

how will a competitive inhibitor look on a graph

Answer 30

same Vmax and increased Km

Question 31

hwo does a noncompetitive inhibitor look on a graph

Answer 31

same Km but decreased Vmax

Question 32

what is an uncompetitive inhibitor

Answer 32

binds to the enzyme substrate complex, not the enzyme. causes a structural distortion where the enzyme becomes inactive.

addition of S does not reverse this since there is no competition for the same binding site

Question 33

what does a regulartory molecule do for allosteric regulation

Answer 33

active site can become available/unavailable with the presence of a regulatory molecule. joins the enzyme via phosphorylation or dephosphorylation

Question 33

what is feedback inhibition

Answer 33

where the end product of a metabolic pathway acts as an inhibitor of the key enzyme causing a stop in the end product being produced