Mcb Biochemistry Flash Cards Quiz #2

Front 1

competitive inhibitor

Back 1

competes with substrate for binding to the active site; binding is reversible and the inhibition can be overcome at very high substrate concentrations; Vm is unchanged but the slope is changed

Front 2

dissociation constant for inhibitor

Back 2

K1 = k-1/k1

Front 3

y-intercept

Back 3

1/Vm

Front 4

slope

Back 4

Km/Vm

Front 5

noncompetitive inhibition

Back 5

KI =KI'; increase the slope, the two lines with and without inhibitor will meet at the x-intercept

Front 6

mixed inhibition

Back 6

lines with and without the inhibitor will not meet at the x-intercept; increase the slope and y-intercept

Front 7

uncompetitive inhibition

Back 7

increase y-intercept but will not increase the slope and thus the lines with and without the inhibitor will be parallel

Front 8

irreversible inhibition or suicide inhibition

Back 8

enzymes can be inactivated when they form covalent bonds with inhibitors.

Front 9

heme

Back 9

porphyrin ring which consists of four linked pyrrole rings

Front 10

proximal histidine

Back 10

bonds to the ferrous iron

Front 11

distal histidine

Back 11

constrains the positions of oxygen or carbon monoxide

Front 12

why does a protein carry here?

Back 12

to prevent the oxidation of ferrous ion; reduce binding efficiency of CO

Front 13

Hemoglobin structure

Back 13

multimer with four subunits; two alpha and two beta

Front 14

myoglobin is half saturated at?

Back 14

.26 kPa

Front 15

hemoglobin is half saturated at?

Back 15

4 kPa

Front 16

binding curve of myoglobin

Back 16

hyperbola

Front 17

binding curve of hemoglobin

Back 17

sigmoidal

Front 18

hemoglobin binds cooperatively

Back 18

this means that the binding of one oxygen molecule promotes the binding of another

Front 19

hill coefficient of hemoglobin

Back 19

2.8 (measure of cooperativity)

Front 20

Bohr effect

Back 20

reducing pH shifts the oxygen binding curve to the right so that oxygen is more easily lost in the tissues

Front 21

CO2 effect

Back 21

when CO2 concentration is raised, moves oxygen binding curve to the right

Front 22

BPG effect

Back 22

causes the P50 to increase from .26 kPa to 4 kPa. At high altitude, the blood concentration of BPG increases twofold over 36 hours promoting the dissociation of oxygen from hemoglobin in the tissues

Front 23

number of contacts between hemoglobin subunits

Back 23

35

Front 24

allosteric transition

Back 24

transition from tense to relaxed state; alpha beta subunit pairs rotate 15 degrees relative to one another during transition

Front 25

H bond change in the allosteric transition

Back 25

B2AspG1 and alpha TyrC7 become broken, new H bond is between B2AsnG4 and alpha1CAspG1

Front 26

mechanism of the Bohr effect

Back 26

lowering of pH favors T state of deoxyhemoglobin and one source of effect is His146 (His HC3). In the T state when its imidazole ring is protonated it forms an ionic bond with AspFG1 in the beta chain which stabilizes the T-state. When it goes to R form, it loses proton and moves inside the hemoglobin molecule

Front 27

BPG

Back 27

four negative charges are neutralized by four positive charges in the central cavity of deoxyhemoglobin; in oxyhemoglobin there is not enough room for BPG

Front 28

fetal hemoglobin

Back 28

has two alpha and two gamma chains; oxygen affinity is higher than adults which allows transfer of oxygen across the placenta towards the fetus

Front 29

Carbonic anhydrase

Back 29

prevents bubbling by increasing the rate of hydration of CO2 to hydrogen ion and bicarbonate

Front 30

sickle cell anemia

Back 30

hemoglobin from these patients migrates more slowly than does normal hemoglobin when running a gel electrophoresis

Front 31

HbA sequence

Back 31

val-his-leu-thr-prop-glu-glu-lys

Front 32

HbS sequence

Back 32

val-his-leu-thr-pro-val-glu-lys; forms a hydrophobic patch on the surface of deoxyhemoglobin.

Front 33

flocculent precipitate

Back 33

lattice of divalent Ig and protein-hapten; should be maximal when the IgG and divalent haptens are in equal concentrations

Front 34

IgG structure

Back 34

consists of two heavy polypeptide chains (53000) and two light polypeptide chains (22,000)

Front 35

epitopes

Back 35

the parts of natural proteins to which antibodies can bind

Front 36

HAt selection

Back 36

hypoxanthine aminopterin and thymidine are involved

Front 37

immunoblot

Back 37

identifies that a particular cell is producing a particular kind of antigen

Front 38

prosthetic groups

Back 38

enzymes that require a bound organic molecule in order to function

Front 39

oxidoreductases

Back 39

transfer electrons in oxidation-reduction reactions

Front 40

transferases

Back 40

participate in intermolecular group transfers

Front 41

hydrolases

Back 41

catalyze hydrolysis

Front 42

lyases

Back 42

participate in reactions involving double bonds

Front 43

isomerases

Back 43

transfer groups with in a (molecule intramolecular transfers) to give isomeric forms

Front 44

ligases

Back 44

condensing enzymes which form C-C, C-S, C-O, C-N, and phosphodiester bonds coupled to cleavage of ATP or some other nucleotide

Front 45

length of transition state

Back 45

10^(-13)

Front 46

K'eq =

Back 46

[P]/[S]

Front 47

delta G' (standard)=

Back 47

-RTlnK'eq

Front 48

velocity of a single substrate

Back 48

V= k[S]

Front 49

velocity for two substrates

Back 49

V= k[S1][S2]

Front 50

do enzymes bind the TS state or the substrate better?

Back 50

TS

Front 51

four theoretical mechanisms of enzyme action

Back 51

1. stabilizing distorted state of the substrate
2. removing a hydration shell that stabilizes the substrate
3. putting two molecules close together and increasing chance of collision
4. aligning molecules properly for reaction

Front 52

Km

Back 52

the substrate concentration that gives the half-maximal velocity

Front 53

turnover number

Back 53

k2; the number of molecules of substrate that go to product per second

Front 54

catalysis constant

Back 54

kcat; can be very high

Front 55

enzyme efficiency

Back 55

kcat/km

Front 56

how high can kcat/km go?

Back 56

10^(8)- 10^(9)

Front 57

what is the efficiency of carbonic anhydrase?

Back 57

8 x 10^(7)