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Unit 6 > "Molecular & Cellular Princ Med Hemoglobin Edward Berry" MARY > Flashcards

"Molecular & Cellular Princ Med Hemoglobin Edward Berry" MARY Flashcards

1
Q

_____ is an intracellular oxygen transport and storage protein.

A

Myoglobin

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2
Q

What is the predominant carrier of oxygen in the circulatory system?

A

Hemoglobin

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3
Q

Where does the steepest gradient in O2 concentration occur?

A

RBC in capillary (20 torr) to surface of myocyte (<5 torr)

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4
Q

O2 diffusion into the mitochondria in a muscle cell is facilitated by:

A

Myoglobin

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5
Q

What group binds oxygen in both hemoglobin and myoglobin?

A

Heme prosthetic group

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6
Q

What are the functions of myoglobin?

A
  1. Intracellular transport of O2 2. Temporary storage of O2 needed for aerobic metabolism of muscle
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7
Q

A molecule of Hb is the tetramer, and consists of four subunits: two __1__ and two __2__, four ___3____ and four __4___.

A
  1. Alpha 2. Beta 3. Hemes 4. O2 binding sites
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8
Q

What is the shape of hemoglobin?

A

Tetrahedron

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9
Q

What is a protomer?

A

Hemoglobin monomers first assemble into rather stable, rigid ab heterodimers called protomers.

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10
Q

What is the basis for the cooperativity seen in the binding curve?

A

R vs T states of hemoglobin

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11
Q

What is the affinity for oxygen when hemoglobin is in the T state?

A

Low

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12
Q

What is the affinity for oxygen when hemoglobin is in the R state?

A

High

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13
Q

Heme is Fe chelated by:

A

protoporphyrin IX

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14
Q

What does the vinyl group of the protoporphyrin look like?

A

CH2=CH

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15
Q

What does the propionate group of the protoporphyrin look like?

A

CH2-CH2-COO-

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16
Q

Draw the pyrrole ring (1 of the 4) found in heme

A

5-sided ring made of mostly single bonds and one double C bond, and one N, bound to C’s by single bonds.

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17
Q

Name another type of heme protein besides myoglobin and hemoglobin.

A

Cytochrome P-450s involved in drug metabolism

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18
Q

T/F: Oxygen changes the absorption properties of Hb.

A

True, that is why oxygenated blood appears redder and brighter than deoxygenated blood.

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19
Q

Name some molecules that bind O2 with higher affinity than Hb, thus acting as poisons if too much is in the blood.

A

CO, NO, H2S, cyanide, azide (CN-), sulfide (S-)

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20
Q

What is the natural state of Fe in Hb?

A

Ferrous, Fe (II)

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21
Q

What happens when Fe in Hb goes from Ferrous (II) to Ferric (III)?

A

If Fe is oxidized from Fe (II) to Fe (III), methemoglobin is made, which is brown-red and nasty colored.

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22
Q

T/F: Methemoglobin binds O2 more tightly than normal (ferrous) Hb.

A

False! MetHb does not bind oxygen

23
Q

What characteristic of blood allows pulse oximeters to monitor O2 saturation?

A

The changes in the absorption spectrum of Hb.

24
Q

Always associate LOW P50 with:

A

High affinity for O2

25
Q

The O2 concentration in blood is: __1__ in venous blood __2__ in arterial blood

A
  1. ~20 torr (Hb is 43% saturated) 2. ~100 torr (Hb is 95% saturated)
26
Q

What is the definition of P50?

A

The pressure at which 50% of oxygen is bound and 50% has been released. P50 of myoglobin = ~2.6 torr P50 of hemoglobin = ~26 torr

27
Q
  1. What is the shape of the myoglobin curve? 2. What is the shape of the hemoglobin curve?
A
  1. Hyperbolic 2. Sigmoidal
28
Q
  1. At high [O2], the dissociation curve is closer to what Hb state? 2. At low [O2], the dissociation curve is closer to what Hb state?
A
  1. R state (curve moves left) 2. T state (curve moves right)
29
Q

Define allostery.

A

An effect of something happening at another site on the molecule.

30
Q

______ is a type of allostery in which what is happening at one site promotes the same thing happening at another identical site.

A

Cooperativity

31
Q

Negative effectors that shift the Hb curve to the right (favor and stabilize the T state) are:

A

BPG, CO2, H+, being in the tissues, so O2 is released.

32
Q

Positive effectors shift the Hb curve in what direction?

A

To the LEFT

33
Q

Why does deoxyHb have much greater O2 affinity than Hb in whole blood?

A

BPG found in whole blood. BPG stabilizes the T state.

34
Q

What is the time course of BPG activity?

A

It works over hours, or longer, as in high-altitude acclimatization.

35
Q

What is the binding ratio of BPG?

A

1:1 (1 BPG equivalent per Hb tetramer)

36
Q

What is the effect of BPG in whole blood?

A

Drives unloading of O2

37
Q

DeoxyHb bound to BPG displays reduced affinity for O2. Therefore, BPG shifts the O2 dissociation curve in what direction?

A

Right

38
Q

Oxygenation of Hb makes it a stronger acid. Hb releases ____ for each O2 it binds.

A

0.6 protons

39
Q

The transition of CO2 to HCO3- in the tissues does what to the pH?

A

Lowers pH –> stabilizes T-state of Hb –> reduces affinity for O2.

40
Q

Name the enzyme that accelerates the reaction: CO2 + H2O H2CO3 HCO3- + H+

A

carbonic anhydrase

41
Q

CO2 + H2O H2CO3 HCO3- + H+ In what direction does this reaction run in the lungs and why?

A

To the left, to produce CO2. CO2 in the lungs is low because of exchange with inhaled air, so in producing the CO2, using up protons, lowering the pH, the affinity of Hb for O2 is increased to promote efficient loading.

42
Q

CO2 combines reversibly with the N-terminal amino groups of blood proteins to for carbamates: R-NH2 + CO2 R-NH-COOH R-NH-COO- + H+ What is this reaction called?

A

Carbamylation, stabilizes the T state of Hb.

43
Q

T/F: Fetal Hb binds O2 with lower affinity in order to properly perfuse developing tissue.

A

False. Fetal Hb binds O2 with HIGHER affinity in order to steal O2 from mom.

44
Q

What is the composition of HbF?

A

Fetal Hb (HbF) is alpha2gamma2, whereas regular Hb is alpha2beta2.

45
Q

What is the difference in functionality between the gamma and beta forms of Hb?

A

The gamma subunit does not bind BPG as tightly, making it more favorable to tight O2 binding.

46
Q

T/F: Myoglobin, a monomer, shows no allosteric effects in O2 binding.

A

True

47
Q

Name and give the subunits for the 3 wild type Hb’s.

A

HbA (alpha2beta2)

HbA2 (alpha2delta2)

HbF (alpha2gamma2)

48
Q

On what subunit is the sickle cell trait found?

A

Glu6 of chain beta. Sickle cell disease is HbS (alpah2beta*2)

49
Q

T/F: HbC is protective against malaria

A

True, but it does not polymerize the way HbS does.

50
Q

HbH is made up of what subunits? What disease is this?

A

HbH is beta4, and is alpha-thalassemia major

51
Q

HbBarts is made up of what subunits? What disease is this? What is the outcome caused?

A
  1. HbBarts is gamma4
  2. Alpha-thalassemia major but worse than HbH
  3. Hydrops fetalis
52
Q

What is the definition of an alpha thalassemia?

A

Defect in production of alpha chains, Note there are 2 HbA genes.

53
Q

Methemoglobinemia involves less O2 delivery to tissues, resulting in what appearance/symptom?

A

Cyanosis

54
Q

What O2 saturation is cause for alarm?

A

<90%

Unit 6 (32 decks)

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