Enzymes

Question 1

enzymes

Answer 1

biological catalysts that speed up the rate of a reaction by lowering the energy of activation
- sensitive to temp, pH, and are specific for specific reactions

Question 2

what happens to enzymes during a reaction?

Answer 2

they are not changed or consumed and do not effect Keq/ equillibrium of a reaction or affect thermodynamic perameters

Question 3

can enzymes make an unfavorable reaction favorable?

Answer 3

no because they do not affect ΔG, ΔS or ΔH

Question 4

t/f: enzymes can increase the rate of a reaction

Answer 4

true

Question 5

t/f: enzymes can alter equilibrium

Answer 5

false

Question 6

t/f: enzymes reduce the activation energy (Ea)

Answer 6

True

Question 7

t/f: enzymes can change Δh, Δg, Δs

Answer 7

false

Question 8

t/f: enzymes are sensitive to temp and pH

Answer 8

true

Question 9

t/f enzymes are consumed during a reaction

Answer 9

false

Question 10

reaction coordinate diagram

Answer 10

shows how the reactants progress to products and how much gibbs free energy changes

Question 11

activation energy

Answer 11

the amount of energy needed to overcome for a reaction to proceed

Question 12

what direction do enzymes speed up a reaction

Answer 12

forward and backward (avoid altering equillibrium)

Question 13

where does an enzyme interact with substrate

Answer 13

at the active site

Question 14

active site

Answer 14

binding site: where substrate binds via intermolecular forces and catalytic site of enzyme

Question 15

orthosteric regulators

Answer 15

interact with an enzyme at its active site

Question 16

allosteric regulators

Answer 16

bind somewhere besides the active site

Question 17

lock and key theory

Answer 17

active site of an enzyme and the substrate fit together like a puzzle with no change in terciary or quartenary structure
- old and outdated model

Question 18

induced fit model

Answer 18

enzyme and substrate are seen as affecting one another. the initial binding causes a conformational shift

Question 19

oxidoreductases

Answer 19

catalyze electron transfer reactions
- example –> dehydrogenases

Question 20

transferase

Answer 20

transfer a functional group between molecules
ex: dna polymerase

Question 21

hydrolase

Answer 21

catalyze hydrolysis
- lactase (add water to break apart)
- proteases

Question 22

lyases

Answer 22

cleave bonds through non-hydrolysis mechanisms
- pyruvate decarboxylase

Question 23

pyruvate decarboxylase

Answer 23

enzyme used in fermenting alcohol
pyruvate –> aldehyde via decarboxylation,

Question 24

isomerases

Answer 24

catalyze isomerization
ribose 5 phosphate isomerase

Question 25

ligase

Answer 25

join molecules together with COVALENT bonds - pyruvate carboxylase

Question 26

pyruvate carboxylase

Answer 26

adds a cooh group to pyruvate to make it oxaloacetate

Question 27

phosphotases

Answer 27

remove phosphates

Question 28

kinases

Answer 28

add phosphates

Question 29

rate limiting step of glycolysis`

Answer 29

pfk1 making 1,6 fructose bisphosphotate

Question 30

what product DIRECTLY inhibits pfk-1

Answer 30

increased ATP levels

Question 31

mechanism of blood clotting

Answer 31

positive feedback

Question 32

feed-forward regulation

Answer 32

an enzyme is regulated by an upstream product

Question 33

pyruvate kinase activity is increased by what

Answer 33

increased levels of fructose 16bisp

Question 34

cooperativity

Answer 34

enzyme has multiple active sites and binding at one site facilitates binding at another - example: hemoglobin

Question 35

what does a cooperativity graph look like

Answer 35

sigmoidal (s shaped) saturation of enzymes (y) and substrate present (x)

Question 36

hill coefficient

Answer 36

degree of cooperativity of an enzyme

Question 37

hill coefficient of >1

Answer 37

positive cooperativity

Question 38

hill coefficient of <1

Answer 38

negative cooperativity (binding of first ligand decreases binding affinity for next)

Question 39

Vmax

Answer 39

maximum rate of reaction for an enzyme to convert a specific reactant into product - all enzymes are saturated - units of substate/ time

Question 40

Km

Answer 40

concentration of substrate where half of the enzymes are saturated (1/2 vmax) - measures the affinity of an enzyme for a substrate

Question 41

michaelis-mentin equation

Answer 41

V = (Vmax[s])/ Km + [s]

Question 42

how does changes in substrate concentration and enzyme affect the km

Answer 42

it does not change km

Question 43

linewiever-burke plots

Answer 43

x axis is -1/ km y axis is 1/vmax

Question 44

what happens on a lineweiver burke plot if vmax is decreased

Answer 44

the y intercept will move up (farther from 0)

Question 45

what happens on a linweiver burke plot if km is decreased

Answer 45

the x intercept will move farther from 0

Question 46

inhibitors

Answer 46

reduce the effictive activity of enzymes - can be reversible or irreversible

Question 47

how do reversible inhibitors interact with enzymes?

Answer 47

through non-covalent interactions

Question 48

how do irreversible inhibitors interact with enzymes

Answer 48

through covalent interacitons

Question 49

competitive inhibitors

Answer 49

reversible - compete with substrate for binding at the active site - vmax stays same, km increases - can be outcompeted by adding more substrate

Question 50

noncompetitive inhibitors

Answer 50

reversible inhibitors that bind to an allosteric site -they can bind to enzyme regardless of whether the substrate is bound or not - reduce vmax and km remains same

Question 51

uncompetitive inhibitor

Answer 51

reversible inhibitor that interacts with the enzyme-substrate complex at an allosteric site - prevents enzyme from letting go of substrate so catalysis is reduced - vmax decreased, km decreased

Question 52

mixed inhibition

Answer 52

inhibitor can bind to the free enzyme at an allosteric site or the E-S complex - VMAX ALWAYS DECREASES and effect on km is variable - if it prefers the active site, km increases - if it prefers ES complex, km decreases

Question 53

effect of competitive inhibition on vmax and km

Answer 53

vmax --> same km --> increase

Question 54

effect of noncompetitive inhibition on vmax and km

Answer 54

vmax --> decreases km --> stays same =

Question 55

effect of uncompetitive inhibition on vmax and km

Answer 55

vmax : decrease km: decrease

Question 56

what kind of inhibition causes a decrease in Vmax and an increase in KM

Answer 56

mixed inhibition where it prefers to bind to free enzyme

Question 57

phosphorylation

Answer 57

kinases add a phosphate group - can be considered activation

Question 58

what amino acid residues are phosphorylated

Answer 58

serine, threonine, tyrosine

Question 59

dephosphorylation

Answer 59

phopshotases remove phosphate groups inactivate residue

Question 60

glycosylation

Answer 60

add a sugar to a molecule

Question 61

zymogens

Answer 61

proenzymes inactive forms that must be cleaved

Question 62

cofactors

Answer 62

inorganic (metal ions) or organic molecules that must be present for an enzyme to function

Question 63

coenzymes

Answer 63

organic cofactors (vitamins)

Question 64

prosthetic group

Answer 64

coenzymes that are tightly bound to an enzyme - heme in hemoglobin

Question 65

holoenzyme

Answer 65

complete enzyme with cofactors/coenyzmes

Question 66

Kcat

Answer 66

turnover rate number of substrate converted to product per second

Question 67

kcat equation

Answer 67

vmax/[E]