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Biochem homemade > Oxygen transport > Flashcards

Oxygen transport Flashcards

1
Q

The oxygen transporter of muscle

A

Myoglobin

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2
Q

Myoglobin contains a prosthetic group called a _____

A

heme molecule

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3
Q

Myoglobin is comprised of _____ aa residues

A

153

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4
Q

The proximal histidine residue (___) forms a _____

A

The proximal histidine residue (F8) forms a direct ligand to the iron

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5
Q

The prosthetic group of myoglobin and hemoglobin, heme, is ______

A

in a deep, non-polar pocket

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6
Q

This sequestering of iron from water (through the hydrophobic pocket ) helps maintain the ______

A

Fe 2+ state

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7
Q

Carbon monoxide (CO) bound heme is also _____ (color)

A

bright red

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8
Q

Since histidine is attached to the whole helix, when oxygen binds the iron, the _____

A

whole helix moves (changes conformation)

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9
Q

Myoglobin can only carry _____ (number) O2

A

1

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10
Q

Impact of change in structure of myoglobin due change in oxygenation state

A

None

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11
Q

Oxygenated heme is ____ (color)

A

bright red

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12
Q

Oxidized heme is ____ (color)

A

brownish

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13
Q

deoxygenated heme is_____ (color)

A

more blue

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14
Q

Hemoglobin comprises of _____ _____ subunits and _____ _____ subunits

A

2 alpha and 2 beta subunits

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15
Q

Hemoglobin (HbA) is a ____ of ab units

A

dimer

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16
Q

Hb is a ____ oxygen binder than myoglobin

A

weaker

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17
Q

Hill coefficient tells you _____

A

The level of cooperatively

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18
Q

n>1 means ______ cooperativity.

A

positive cooperatively=binding of one ligand promotes binding of another.

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19
Q

n=1 means _____ cooperativity.

A

no

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20
Q

n<1 means___

A

negative cooperativity

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21
Q

Hemoglobin exists in __ and __ forms

A

T and R

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22
Q

Which form (T/R) has no oxygen bound

A

T

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23
Q

Which form (T/R) has oxygen bound

A

R

24
Q

Which form (T/R) is more stable, and why?

A

T, because it contains more electrostatic and hydrogen bonds or “tense”

25
Q

Both _____ and _____ reduce the O2 affinity of hemoglobin. These effectors are called____

A

H+ and CO2. Allosteric effectors

26
Q

Both H+ and CO2 allow hemoglobin to deliver _______

A

more oxygen to actively metabolizing tissues

27
Q

Hb releases O2 in muscles upon binding of

A

CO2

28
Q

Hb releases CO2 in lungs upon binding of

A

O2

29
Q

_____ lowers the affinity of hemoglobin for oxygen.

A

Bisphosphoglycerate (BPG)

30
Q

Normal blood concentration of BPG

A

5mmol/L

31
Q

BPG rises under _____, allowing oxygen to be efficiently delivered to tissues

A

low oxygen conditions

32
Q

In HbA, BPG binds to ______

A

a pocket formed by the beta subunits (many positive charges)

33
Q

Fetal hemoglobin (HbF) is _______. Adult hemoglobin (HbA) is ______.

A

Fetal hemoglobin (HbF) is alpha2-gamma-2. Adult hemoglobin (HbA) is alpha-2-beta-2.

34
Q

HbF and HbA are VERY similar in sequence, structure, and function, except in their ability to bind _____

A

BPG

35
Q

BPG binds with lesser affinity to HbF, because

A

HbF has fewer positive charges in its corresponding pocket than the pocket made by the two beta subunits on HbA

36
Q

Because HbF binds BPG less well, it ______

A

binds oxygen with higher affinity

37
Q

2 diseases of hemoglobin

A
  1. methemoglobinemia

2. sickle-cell anemia

38
Q

Nonpathological substitution

A

Mutations that have no effect on hemoglobin function

39
Q

Hemoglobin S

A

disrupt hemoglobin structure or function

40
Q

Characterized by insoluble Hemoglobin (HbS). Result is clogging of capillaries and
general organ damage causing pain

A

Sickle Cell anemia. 1 in 13 African Americans affected

41
Q

The molecular defect in HbS of sickle cell anemia is

A

A point mutation converting glutamate to valine on the exterior of the beta subunit

42
Q

Sickle cell mutation can be detected using

A

electrophoresis

43
Q

Sickling is made worse by

A

decreased oxygen

44
Q

A _____ is formed in both HbA and HbS when in the deoxy form

A

hydrophobic hole

45
Q

A _____ is present on the b subunit of HbS in both deoxy and oxy forms

A

hydrophobic knob

46
Q

The deoxy form of HbS can form ______

A

long polymers

47
Q

Treatment of Sickle Cell Anemia

A
  1. Antibiotic therapy (to prevent secondary infections)
  2. Hydroxyurea (stimulates the production of HbF)
  3. Bone marrow transplantation (replaces HbS with HbA)
  4. Gene therapy (Phase I/II)
48
Q

Methemoglobinemia

A

Heme groups become +3 ad cannot carry oxygen

49
Q

2 ways to develop methemoglobinemia

A

Inherited: Mutations in heme-binding pocket of Hb can promote HbM

Environmental: Ingestion of nitrates and nitrites can promote HbM.

50
Q

Clinically present with shortness of breath, cyanosis, mental status changes

A

Methemoglobinemia

51
Q

Methemoglobinemia is diagnosed by

A

the absorption spectrum of the blood (peak at 630nm)

52
Q

Ways to treat the disease:

A

Reducing agents (such as Vitamin C and methylene blue)

53
Q

Oxygen binds to

A

heme

54
Q

Carbon dioxide binds to

A

site outside of heme

55
Q

Carbon monoxide binds to

A

heme

56
Q

BFG binds to

A

a pocket formed by the &beta-subunits

57
Q

H+ binds to

A

histidine and the N-terminal α-amino groups (of the α-subunits)

Biochem homemade (3 decks)

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