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BMSC 200 > Module 5 > Flashcards

Module 5 Flashcards

1
Q

what is a ligand?

A

a molecule reversibly bound by the protein

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2
Q

what are the 2 ligands of hemoglobin?

A
  1. oxygen
  2. 2,3 BPG
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3
Q

what is an induced fit?

A

changes in protein confirmation caused by ligand binding

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4
Q

what are the advantages and disadvantages of transition metals?

A
  1. they can bind oxygen
  2. but they produce free radicals
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5
Q

is o2 soluble in aqueous solutions?

A

very little

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6
Q

what amount of oxygen that can be delivered within the organism can limit…

A

its size

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7
Q

what is myoglobin

A

monomeric molecule that facilitates oxygen storage in peripheral tissue

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8
Q

where is myoglobin found?

A

in muscles

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9
Q

myoglobin tertiary structure

A

binds 1 o2 with high affinity

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10
Q

is myoglobin’s curve closer to y or x axis

A

y axis bc it has higher affinity

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11
Q

what is hemoglobin?

A

tetrametic protein that transports O2 from lungs to the periphery

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12
Q

where is hemoglobin found?

A

in red blood cells

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13
Q

what structure does hemoglobin represent?

A

quaternary structure that transports O2 with lower affinity

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14
Q

how many O2 molecules can hemoglobin bind to?

A

4

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15
Q

what shape of curve does hemoglobin represent?

A

sigmoidal (S shaped)

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16
Q

what is a heme group?

A

cellular iron that makes it less reactive

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17
Q

what does a heme group consist of?

A

protoporphyrin ring system bound to a single iron atom

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18
Q

what do both myglobin and hemoglobin use to enable O2 binding?

A

a heme group

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19
Q

what is the 6th position in heme group?

A

position for O2 binding

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20
Q

what does distal histidine do?

A

provides a stabilizing interaction for bound O2

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21
Q

what is the myoglobin structure?

A

small globular protein consisting of single polypeptide and a heme group

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22
Q

what is the equation for fraction saturation?

A

[PO2] / [PO2] + [P50]

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23
Q

what value is PO2 in the lungs?

A

100 torr

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24
Q

what is the value of PO2 in the periphery?

A

20 torr

25
Q

what is an allosteric protein?

A

can adopt 2 different conformations

26
Q

what 2 confirmations can allosteric proteins form?

A

T & R states

27
Q

what is the T state of an allosteric protein?

A

inactive state (deoxyhemoglobin)

28
Q

what is the R state of an allosteric protein?

A

active state, always increasing hemoglobin’s affinity for O2

29
Q

what are allosteric modulators?

A

small molecules that can bind to a proton and influence the equilibrium between T & R states

30
Q

what do allosteric activators do?

A

stabilize the R state & speed things up

31
Q

what do allosteric inhibitors do?

A

stabilize the T state & slow things down

32
Q

what does homotropic mean?

A

when ligand & modulator are the same

33
Q

what does heterotropic mean?

A

when ligand and modulator are different

34
Q

what 2 things does O2 serve as?

A
  1. ligand
  2. allosteric molecule
35
Q

how are the binding & release of O2 regulated?

A

allosterically

36
Q

what is the position of the iron atom at the T state?

A

outside heme ring

37
Q

what is the position of the iron atom in the R state?

A

inside heme ring

38
Q

what is the purpose of 2,3 BPG?

A

to decrease hemoglobin’s affinity for O2

39
Q

how many units of negative charge does 2,3 BPG have?

A

5

40
Q

true or false: fetal hemoglobin has a higher affinity for O2than maternal hemoglobin

A

true because bc of less positive charge

41
Q

what is the 1 amino acid difference between fetal and maternal hemoglobin?

A

HIS 143 is replaced by SER

42
Q

what does affinity mean?

A

attraction

43
Q

what is the Bohr effect?

A

lower pH= decreased hemoglobin affinity for O2

44
Q

what is the purpose of the Bohr effect?

A

to coordinate increased release of O2 to tissues

45
Q

what occurs in mechanism 1?

A

CO2 is taken up into red blood cells & converted to bicarbonate

46
Q

what enzyme is used in mechanism 1?

A

carbonic anhydrase

47
Q

what occurs in mechanism 2?

A

CO2 can form a covalent linkage to the N terminus to form carbaminohemoglobin

48
Q

does carbamino hemoglobin or hemoglobin have a lower O2 affinity?

A

carbamino

49
Q

what is sickle cell anemia?

A

disease of hemoglobin that causes red blood cells to sickle

50
Q

what happens in the T state of sickle cell anemia?

A

hemoglobins link together

51
Q

what causes red blood cells to sickle?

A

the fibers

52
Q

where is sickle cell anemia higher?

A

in areas where malaria is present

53
Q

why is sickle cell anemia increased in areas with malaria?

A

bc infection decreases red blood cell pH

54
Q

what is hemocyanin?

A

uses copper rather than iron to transport oxygen

55
Q

is there a heme group in hemocyanin?

A

no

56
Q

how many copper atoms bind to 1 O2 molecule in hemocyanin?

A

2

57
Q

Hemoglobin weighs ( ) times as much as myoglobin

A

4

58
Q

O2 serves as a ( ) for hemoglobin

A

homotropic allosteric activator

59
Q

2,3 BPG acts as a ( ) for hemoglobin

A

heterotropic allosteric inhibitor

BMSC 200 (10 decks)

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