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Respiratory > Structure and function of hemoglobin > Flashcards

Structure and function of hemoglobin Flashcards

1
Q

What are the main components of HbA?

A

2-alpha chains
2-beta chains
Heme

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2
Q

What are the main components of HbA2

A

2-alpha chains
2-sigma chains
Heme

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3
Q

What are the main components of HbF?

A

2 alpha chains
2 gamma chains
Heme

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4
Q

What are the main components of HbA1c?

A

2 alpha chains
2 beta chains
Glucose

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5
Q

What is the attachment point of the glucose on HbA1c?

A

Amino group of the N-terminal valine of the beta-globin chain

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6
Q

What chromosome carries the alpha-globin genes?

A

Chromosome 16

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7
Q

What chromosome carries the beta-globin genes?

A

Chromosome 11

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8
Q

What are the embryonic hemoglobins?

A

Hb Gower 1
Hb Gower 2
Hb Portland

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9
Q

What, located upstream of the beta-globin genes, plays a significant role in expression?

A

Locus control region

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10
Q

What are the components of heme?

A

Ferrous iron - Fe++
Protoporphyrin IX

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11
Q

What are the 6 bonds to the ferrous iron in heme?

A

4 to the nitrogens in the porphyrin ring
1 to the histidine of globin
1 left available to bind to O2

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12
Q

How many heme are in each hemoglobin?

A

4

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13
Q

What is the function of the distal histidine in the heme binding site?

A

Stabilizes O2 binding to Fe++

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14
Q

What is the T form of Hgb?

A

Deoxygenated form with a low affinity for oxygen

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15
Q

What is the R form of Hgb?

A

Oxygenated form with high O2 affinity

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16
Q

What is the purpose of cooperative binding?

A

Allows Hgb to deliver more O2 to tissues

17
Q

What is the function of myoglobin?

A

Reservoir of oxygen and as an oxygen carrier in muscle cells

18
Q

What is the shape of the oxygen dissociation curve for myoglobin?

A

Hyperbolic

19
Q

What is the shape of the oxygen dissociation curve for hemoglobin and why?

A

Sigmoidal because of cooperative binding

20
Q

What factors affect the unloading and loading of O2 to hemoglobin?

A

PO2
pH
PCO2
Concentration of 2,3-BPG

21
Q

What is the influence of low pH and increased PCO2 on the oxygen dissociation curve?

A

Increased unloading, shift curve to the right

22
Q

What will happen to the oxygen dissociation curve if Hgb has a higher affinity for oxygen?

A

It shifts to the left

23
Q

What is the function of 2,3-BPG and when is its concentration higher?

A

Decreases oxygens affinity for Hgb

Hypoxia and anemia

24
Q

What occurs to the oxygen dissociation curve in chronic anemia?

A

Curve shifts to right –> increased O2 disassociation

25
Q

What occurs to the oxygen dissociation curve during a panic attack?

A

Curve shift to the left –> hypoventilation decreased PCO2

26
Q

What occurs to the oxygen dissociation curve in hypothermia?

A

Shifts to the left

27
Q

What component performs the buffering action of Hb?

A

Imidazole group of histidine residues binds H+

28
Q

What is the defect in HbS?

A

Glutamic acid at 6th position of beta-globin chain is replaced by valine

29
Q

What is the defect in HbC?

A

Glutamic acid in the 6th position of beta-globin is replaced by lysine

30
Q

What is the defect in HbSC?

A

Both HbS and HbC present

31
Q

What is defect in thalessemia?

A

Imbalance in the synthesis of globin chains

32
Q

What is the defect in methemoglobinemias/HbM)

A

Oxidation of heme iron from ferrous to ferric (Fe++ to Fe+++)

33
Q

Is HbM/metHb able to bind oxygen?

A

No

34
Q

What characterizes HbM?

A

Chocolate cyanosis –> brown colored blood with cyanosis

35
Q

What enzyme may be deficient in HbM?

A

NADH-metHb reductase

36
Q

What is the treatment for metHb?

A

Methylene blue

37
Q

What can cause acquired metHb?

A

nitrate drugs

38
Q

What changes to the oxygen dissociation curve are seen with CO?

A

Shifts curve to the left
Lowers plateau
Becomes hyperbolic

Respiratory (15 decks)

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