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HEM Exam 1 > Hemoglobin and Myoglobin > Flashcards

Hemoglobin and Myoglobin Flashcards

1
Q

where in the body does Hb bind O2

A
  • in the alveoli of the lungs
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2
Q

where in the body does Hb deliver O2

A
  • to tissues throughout the body
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3
Q

how does Hb assist in maintaining acid-base balance in the body

A
  • binding some CO2 produced by metabolism

- releasing CO2 when Hb reaches the lungs

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4
Q

function of Hb dependent upon

A
  • partial pressure gradients of O2 or CO2
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5
Q

partial pressure of a gas equal to

A

atmospheric pressure x fraction of atmosphere composed of that gas

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6
Q

significance of different of partial pressure between lungs, tissues, and blood

A
  • driving force for gas exchange
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7
Q

myoglobin synthesized where

A
  • inside muscle cells

- skeletal muscle, smooth muscle, cardiac muscle

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8
Q

function of myoglobin

A
  • stores oxygen in muscle cells for use at times of high metabolic demand
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9
Q

myoglobin content varies by

A
  • skeletal muscle fiber type

- IA > IIA > IIB

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10
Q

percentage and type of helix found in myoglobin

A
  • 80% alpha helical
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11
Q

order of structure in myoglobin

A
  • closely packed tertiary structure
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12
Q

heme in structure of myoglobin

A
  • single heme molecule covalently bound
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13
Q

myoglobin binding of oxygen

A
  • binds one O2 molecule at heme
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14
Q

molecule on inside of heme ring

A
  • Fe2+
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15
Q

heme ring hydrophobic or hydrophilic

A
  • hydrophobic
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16
Q

polypeptide chains hemoglobin

A
  • 2 alpha

- 2 beta

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17
Q

polypeptide chain in myoglobin

A
  • single polypeptide chain
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18
Q

amount of O2 bound by hemoglobin

A
  • can bind 4O2 at once
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19
Q

hemoglobin interactions between subunits

A
  • strong hydrophobic interactions between alpha 1 and beta 1
  • and alpha 2 and beta 2
  • weaker polar interactions between a1B1 and a2B2
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20
Q

HbA composition

A
  • a2B2

- quaternary higher order conformation

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21
Q

significance of HbA

A
  • glycosylation is marker for chronically elevated blood sugar
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22
Q

HbA2 composition

A
  • a2 delta 2
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23
Q

HbF composition

A
  • a2y2
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24
Q

thalassemias

A
  • imbalance in globin chain synthesis
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25
Q

what forms coordinate covalent bonds to Fe2+ in heme

A
  • pyrrole rings
26
Q

purpose of hydrophobic chains from pyrrole rings

A
  • interact with a/B globin chains to stabilize heme binding
27
Q

class of pigments that heme belongs to

A
  • porphyrins
28
Q

binding curve of myoglobin

A
  • hyperbolic

- single constant affinity for O2

29
Q

P50 of myoglobin

A
  • 2.8 torr
30
Q

binding curve of hemoglobin

A
  • sigmoidal

- changing affinity for O2 over the binding curve

31
Q

P50 of hemoglobin

A
  • 26 torr
32
Q

P50 definition

A
  • the partial pressure of O2 at which 50% of O2 binding sites are occupied
33
Q

two conformation of Hb

A
  • taught

- relaxed

34
Q

taught conformation favors which form

A
  • deoxy

- O2 release

35
Q

relaxed conformation favors which form

A
  • oxy

- O2 binding

36
Q

O2 regulation of hemoglobin

A
  • affects equilibrium between T and R forms

- positive allosteric regulator of Hb O2 binding

37
Q

movements of proximal and distal histidines cause

A
  • attached alpha helices to move

- causes conformational change at interface of each aB dimer in the Hb molecule

38
Q

2,3-DPG on hemoglobin binding curve

A
  • shifts right
39
Q

2,3-DPG acts on hemoglobin

A
  • stabilized T (deoxy) state

- allow Hb-bound-O2 to dissociate and supply O2 to tissues operating at a high metabolic rate

40
Q

2,3-DPG and hypoxia

A
  • makes O2 release by Hb more responsive to hypoxia

- allows more O2 release at low pO2

41
Q

physiological changes that cause change in 2,3-DPG levels

A
  • COPD
  • high altitude
  • chronic anemia
  • pregnancy
42
Q

Haldane effect

A
  • high pO2 increases binding of O2 to Hb
  • less binding of H+ and CO2
  • O2 is affecting the affinity of Hb for CO2/H+
  • more CO2 delivery to the lungs from tissues
43
Q

Bohr Effect

A
  • high CO2 and high protons
  • protons (due to lower pH) in RBCs bind to Hb
  • favor T state, favoring O2 release to the tissues
  • CO2/H+ are affecting the affinity of Hb for O2
  • more O2 release to tissues from lungs
44
Q

increase in pH favors

A
  • O2 binding

- shifts left

45
Q

decrease in pH favors

A
  • O2 release

- shifts right

46
Q

fetal hemoglobin versus adult hemoglobin A

A
  • fetal hemoglobin has a higher affinity for oxygen
47
Q

HbF and 2,3-DPG

A
  • binds 2,3-DPG very poorly because cavity is not as positively charged
48
Q

O2 released by maternal HbA

A
  • bound by fetal HbF

- transported to fetal tissue

49
Q

the most common Hb variant associated with significant pathology in the Us

A
  • B^s variant
  • caused by mutation at position 6 of beta globin gene
  • changes Glu to Val
50
Q

individuals homozygous for B^s allele or heterozygous for B^s and B-thalassemia allele

A
  • produce significant amount of HbS

- have sickle cell disease

51
Q

importance of deoxy HbS

A
  • forms long polymers within the erythrocyte

- shortens lifespan of RBCs

52
Q

competitors of Hb A at the iron binding site

A
  • cyanide (CN-)
  • carbon monoxide (CO)
  • nitrogen dioxide (NO2)
  • hydrogen sulfide (H2S)
  • all inhibit oxygen binding
53
Q

effect of competitors of HbA on iron

A
  • do not change oxidation status of iron

- remains Fe2+

54
Q

carboxyhemoglobin

A
  • stable complex of carbon monoxide and heme in Hb

- forms more readily than oxyhemoglobin

55
Q

importance of electronic environment of distal (O2-binding) side of heme

A
  • prevents oxidation of Fe2+ to Fe3+ by the bound O2

- would result in O2 release

56
Q

mutations that change any of the 3 amino acids on the distal side of heme result in

A
  • result in hereditary methemoglobinemia
57
Q

hereditary methemoglobinemia characterized by

A
  • cyanosis

- brown color to blood

58
Q

hereditary causes of methemoglobinemia

A
  • mutations in PPP, especially G-6-PD deficiency

- mutations in cytochrome b5 reductase

59
Q

role of glutathione

A
  • normally reduces reactive oxygen species thereby preventing formation of methemoglobin
60
Q

deficiency of methemoglobinemia may not present until

A
  • challenged by increased levels of activated O2 species
61
Q

cytochrome b5 reductase importance

A
  • reduces Fe3+ in methemoglobin to Fe2+

HEM Exam 1 (22 decks)

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