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Chem/Phys Exam 4 > Hemoglobin > Flashcards

Hemoglobin Flashcards

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1
Q

Hemoglobin

A

an allosteric oxygen-binding protein that carries oxygen from the lungs to the tissues for cellular respiration

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2
Q

Hgb consists of how many subunits?

A

Four total subunits 2 a subunits (141 amino acids each) 2 b subunits (146 amino acids each)

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3
Q

Tetramer

A

Hgb is a tetramer (tetra=four) for containing 4 subunits

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4
Q

Heme Moiety

A

Each subunit has a heme moiety which can bind one O2.

Therefore, a single hgb molecule can bind up to 4 oxygen molecules.

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5
Q

Deoxyhemoglobin

A

No oxygen bound to the hemes. Large cleft.

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6
Q

Oxyhemoglobin

A

Small cleft.

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7
Q

Affinities of oxygen binding to Hgb

A

The first oxygen binds with the lowest affinity, each subsequent oxygen binds with higher affinity. This causes the sigmoidal (s-shape) uptake curve.

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8
Q

Locations of Oxygen saturation

A

In the lungs, oxygen tension is high and Hgb is nearly saturated with oxygen.

In deep tissues, oxygen tension is low and hemoglobin releases half of its oxygen.

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9
Q

Saturated

A

each hgb holds 4 oxygen molecules

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10
Q

Allosteric Effect

A

cooperative binding (increasing binding affinity) is due to an allosteric effect where binding to one site affedts the binding at another site.

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11
Q

Why don’t we have much deoxyHgb in our blood?

A

Because most of the hemoglobin is bound to oxygen.

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12
Q

Protoporphyrin and the Formation of Heme

A

Ligation of protoporphyrin IX with an Iron atom (Fe) results in the formation of heme.

The 4 bonds to Fe are to the nitrogens (coordination sites) of the protoporphyrin group.

In Hgb the 5th Fe bond is to histadine residue in the protein mortion. When oxygen is present it binds to the 6th coordination site of Fe.

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13
Q

Deoxyhemoglobin

A

Fe+2

Fe+2 is not bound in deoxy form, but will bind O2 and CO when each is present

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14
Q

Oxyhemoglobin

A

Fe+2…O2

Ferrous iron is bound to oxygen. After one O2 is bound, others bind more readily because of conformation change.

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15
Q

Carboxyhemoglobin

A

Fe+2…CO

Ferrous iron is bound to CO. This forms a stronger bond than with O2

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16
Q

Methemoglobin

A

Fe+3

The iron is in the ferric form and will NOT bind O2 or CO. Oxidation of Fe+2 to Fe+3 is caused by oxidants such as chlorates, nitrates, and nitric oxide (NO)

17
Q

Sulfmethemoglobin

A

Fe+3…SH

Rare, in H2S (hydrogen sulfide) toxicity. Blood is a purple to green color and unable to bind oxygen.

18
Q

Cyanmethemoglobin

A

Fe+3…CN

Cyanide poisoning. Iron must be ferric before it will bind CN. This property of methemoblobin can be used in cyanide poisoning to sequester CN.

If you suspect cyanide poisoning, you can oxidize the Hgb and that Hgb will then bind with cyanide

19
Q

Fetal hemoglobin

A

Has a slightly higher affinity for O2 than adult hgb (left shift)

20
Q

Oxygen Saturation Formula

A
21
Q

SaO2

A

arterial oxygen in RBCs.

22
Q

SaO2 is independent of what?

A

independent of the amount of Hgb present or forms of Hgb present

23
Q

Blood Oxygen Content =

A

Concentration of Hgb x % saturation of Hgb + O2 stabilized in plasma

24
Q

Blood Oxygen Content of normal person

A

15g Hgb/100mL blood

Each gram of Hgb holds 1.34 mL of O2

Therefore, Hgb in 100mL (dL) of blood can bind up to 20mL of O2

20mL of O2/dL blood = 20% vol

25
Q

Right Shift of Oxy-Hgb Dissociation Curve

A

Hgb has less affinity for oxygen and is caused by:

1) increased H+ (decreased pH)
2) increased CO2 (increases carbonic acid which decreases pH)
3) increased temp
4) increased 2,3 DPG metabolic product

26
Q

Left Shift

A

Hgb has MORE affinity for oxygen and is caused by

1) decreased H+ (increased pH)
2) decreased CO2
3) decreased temp
4) decreased 2,3 DPG

27
Q

Bohr Effect

A

the effect of CO and H+ ions to shift the oxy-hgb dissociation curve

28
Q

CO affinity for Hgb

A

CO has a 200x greater affinity for Hgb than O2.

29
Q

Oxygen P50 of Arterial Blood

A

27mmHg (27/0.135=200)

CO will bind to Hgb at a MUCH lower pressure

30
Q

pH

A

arterial - 7.35 - 7.45

venous - 7.32 - 7.42

31
Q

pCO2

A

arterial - 35-45 mmHg

venous - 41-51 mmHg

32
Q

PO2

A

adults: 80-100 mmHg art

25-40 mmHg venous

Over age 65: 75-85 mmHg arterial

Newborn: 60-70 mmHg arterial

33
Q

Normal arterial O2 saturation

A

97 - 100%

34
Q

O2 content

A

men: 17.5 - 23 vol%
women: 16 - 21.5 vol%

35
Q

p50

A

27mmHg arterial

Chem/Phys Exam 4 (10 decks)

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