quiz 3 Flashcards

1
Q

describe myoglobin

A

a monomer
small and compact

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2
Q

where is myoglobin found? why?

A

muscle tissue for oxygen storage

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3
Q

what does myoglobin contain

A

8 alpha helices
prosthetic heme groups

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4
Q

what does myoglobin do

A

reversibly binds O2

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5
Q

describe hemoglobin

A

a porphyrin ring system in a hydrophobic pocket with an iron at the center for covalent bonds

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6
Q

how can the iron be formed

A

can be ferrous (Fe2+) or ferric (Fe3+)

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7
Q

what are the 6 coordination sites of ferrous iron

A

4 pyrrole N
1 proximal histidine
1 O2
1 histidine to O2

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8
Q

what function does histidine play

A

keeps heme coordinated in protein
keeps other hemes from binding

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9
Q

define binding affinity

A

ligand (L) binding to protein (P)

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10
Q

BA equations:

A

P+L=PL
Keq=PL/[P][L]
Ka= PL/[P][L]
dissociation: Kd=[P][L]/[PL]

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11
Q

what does an increased Ka cause?

A

stronger binding

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12
Q

what does an increased Kd cause?

A

weaker binding

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13
Q

what is the equation for fractional saturation

A

occupied binding sites/total binding sites
OR
[PL]/[PL]+[P]

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14
Q

describe a stronger binding

A

left curve
lower Kd
less [L] needed

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15
Q

describe a weaker binding

A

right curve
higher Kd
more [L] needed

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16
Q

define hyperbolic

A

one binding site

17
Q

define KD

A

concentration of O2 when half of mb binds to O2

18
Q

where is hemoglobin found

A

in red blood cells

19
Q

define heterotetramer

A

4 subunits

20
Q

define cooperative binding

A

binding of ligand to one site increases binding affinity for another ligand at another site

21
Q

describe deoxygenated

A

heme is domed and nonpolar

22
Q

describe oxygenated

A

heme is planar and polar

23
Q

describe deoxyhemoglobin

A

no bound O2
heme ring is not planar

24
Q

describe oxyhemoglobin

A

O2 is bound
heme ring is planar
relaxed (R) conformation

25
describe conformational switch
O2 binding pulls iron into plane of heme histidine is pulled up with iron entire F helix moves
26
define allostery
conformational switches underlie cooperatively transmits change in one subunit across the interface of the next subunit 15° rotation
27
describe concerted heme bonding
protein found at T or R binds to single subunit stabilizes R state more complex
28
describe sequential heme bonding
protein found at T and R does not convert only to R state alters affinity of adjacent subunits shifts equilibrium to R state
29
describe positive effectors
increase Hb affinity for O2 shifts equilibrium to R state
30
describe negative effectors
decreases Hb affinity for O2 shift equilibrium to T state