enzymes

Question 1

enzymes

Answer 1

incredibly important as biological catalysts

a biological molecules with catalytic activity; includes many proteins and some RNA molecules. Enzymes are specified for target substrate molecules

Question 2

catalysts

Answer 2

do not impact the thermodynamics of a biological
reaction

the delta H ran and equilibrium position do not change

they help the rxn PROCEED at a much faster rate

Question 3

key points about enzymes

Answer 3

1. lower activation energy
2. increase the rate of rxn
3. are not chgd or consumed in the run (meaning they appear in both reactants and products)
4. are pH and temp-sensitive, with optimal activity at specific pH ranges and temps
5. do NOT affect the overall delta G of the rxn
6. are specific for a particular run or class of rxns

Question 4

enzyme specificity

Answer 4

a given enzyme will only catalyze a single rxn or class of rxns with these substrate, which are molecules upon which an enzyme act

Question 5

oxidoreductase

Answer 5

catalyzed oxidation reduction rxns, the transfer of electrons btwn biological molecules

often have cofactor as electron carrier (NAD+/NADP+)

electron donor= REDUCTANT

electron acceptor= OXIDANT

Question 6

transferases

Answer 6

catalyze the movement of a functional group from one molecules to another

KINASES ARE A MEMBER OF THIS CLASS- transfer of a phosphate grp

Question 7

hydrolyses

Answer 7

catalyze the breaking of a compound into two molecules using the addition of water

Question 8

phosphatase

Answer 8

an example of a hydrolyse

it cleaves a phosphate grp from another group

other examples of hydrolyses are peptidases, nucleases, and lipases

Question 9

lyases

Answer 9

catalyze the cleavage of a single molecules into two products DO NOT REQUIRE WATER, DO NOT ACT AS OXIDOREDUCTASES

the synthesis of two molecules into a single molecules may also be catalyzed by a lyase– referred to as a synthases (usually smaller molecules)

Question 10

isomerases

Answer 10

catalyze the rearrangement of bonds within a molecules

can also be oxidoreductases, transferases, lyases, depending on the mech of the enzyme

catalyze rxns btwn stereoisomers as well as constitutional isomers

Question 11

ligases

Answer 11

catalyze addition or synthesis rxns, generally btwn large similar molecules, and often require ATP

more likely to be encountered in nucleic acid synthesis and repair on test day!!

Question 12

endergonic rxn

Answer 12

one that requires energy output (delta G>0)

Question 13

exergonic rxn

Answer 13

one which energy is given off (delta G <0)

Question 14

catalyses make it easier to for the substrate to reach the __

Answer 14

transition state

Question 15

active site

Answer 15

location within the enzyme where ether substrate is held during the chemical rxn

assumes a defined spatial arrangement in the enzyme substrate complex, which dictates th specificity of that enzyme for a molecules or group of molecules

h bonding, ionic interactions, and transient covalent bonds within the active site all stabilize this spatial arrangement and contribute to the efficiency of th enzyme

Question 16

lock and key theory

Answer 16

suggests the the enzymes active site is already in the appropriate conformation for the substrate to bind

Question 17

induced fit model

Answer 17

MORE SCIENTIFICALLY ACCEPTED MODEL

the interaction requires energy, and therefore, the adjustment to fit and the inducting of a chg in the shape of the enzyme is endergonic. letting go of the substrate is exergonic

Question 18

cofactors/coenzymes

Answer 18

nonprotein molecules that are required by many enzymes

tend to be small in size so they can bind to the active site of the enzyme and participate in the catalysis of the rxn, usually by carrying chg thru ionization, protonation, or deportation

usually kept at low conc in cell

Question 19

apoenzymes

Answer 19

enzymes without their cofactors

Question 20

holoenyzmes

Answer 20

enzymes with their cofactors

Question 21

prosthetic groups

Answer 21

tightly bound cofactors or coenzymes that are necessary for enzyme function

Question 22

B1

Answer 22

thiamine

Question 23

B2

Answer 23

riboflavin

Question 24

B3

Answer 24

niacin

Question 25

B5

Answer 25

pantothenic acid

Question 26

B6

Answer 26

pyridoxal phosphate

Question 27

B7

Answer 27

biotin

Question 28

B9

Answer 28

folic acid

Question 29

B12

Answer 29

cyanocobalamin

Question 30

saturation

Answer 30

in MM kinetics, after Vmax, addition more substrates wouldn’t change the rxn velocity much because all the enzymes are saturated with substrates

Question 31

Hill coefficient

Answer 31

cooperatively can also be quantified using this numerical value

indicates the nature of binding by the molecule

• if over 1, positively cooperative binding is occurring
• if less than, neg cooperative binding is occurring, such that after one ligand is bound the affinity of the enzymes for further ligand(s) decreases
• if =1, the enzyme doesn’t exhibit cooperative binding

Question 32

enzymes activity=enzyme velocity=enzyme rate

Answer 32

heavily influenced by its environment, in particular temperature, acidity of alkalinity (pH), and high salinity have sig effects on the ability of an enzyme to carry out its function

Question 33

feedback regulation

Answer 33

a process where the enzymes are often subject to regulation by products further down a given metabolic pathway

Question 34

feedback forward regualtion

Answer 34

enzymes may be regulated by intermediates that precedes the enzymeint he pathway, less often

Question 35

feedback inhibition=negative feedback

Answer 35

helps maintain homeostasis

once we have enough of a given product, we want to turn off the pathway that creates that product, rather than creating more

the product may bind to the active site of the enzyme or multiple enzymes that acted earlier in its biosynthetic pathway, comptitively inhibiting these enzymes and making them unavailable for use

Question 36

reversible inhbition

Answer 36

four types: competitive, noncompetitive, mixed, uncompeititve

Question 37

competitive inhibition

Answer 37

occupancy of the active site

can be overcome by adding more substrate so the substrate to inhibitor ration is higher

will not alter vale of Vmax

increases the measured vale of Km

Question 38

noncompetitive inhibitors

Answer 38

bind to allosteric site instead of the active site, induces a chg in enzyme conformation. two molecules do not compete for the same site, so noncompetitive and cannot be overcome by adding more substrate

decreases vmax

doesn’t alter Km

Question 39

missed inhibition

Answer 39

when an inhibitor can bind to either the enzyme or the enzyme substrate complex, but has a different affinity for each

do not bind at the active site, but at an allosteric site

alters Km, depending on the preference of the inhibitor for the enzyme vs the enzyme substrate complex. if prefers enzyme, Km increase (powers affinity). if prefers enzyme substrate complex, lowers Km (increases affinity)

Vmax is decreased

Question 40

uncompetitive inhibition

Answer 40

bind only to the enzyme substrate complex and essentially lock the substrate in the enzyme, preventing its release

Km decreases

Vmax decrease

Question 41

irreversible inhibition

Answer 41

allosteric enzymes, covalently modified enzymes, and zymogens

Question 42

allosteric enzymes

Answer 42

multiple binding sites

alternate btwn an active an dan inactive form (cannot carry out he enzymatic rxn).

molecules that bind to the allosteric site ay be either allosteric activators or allosteric inhbitors

Question 43

cov modified enzymes

Answer 43

can be activated or deactivated by phosphorylation or dephosphorylation or glycosylation (cov attachement of sugar moieties)

Question 44

zymogens

Answer 44

contain catalytic domain and regulatory domain, which must be either removed or altered to expose the active site. are used to eighty control certain enzymes.