Resp - Physio (Hemoglobin & Oxygen) Flashcards

Pg. 597-598 in First Aid 2014 Sections include: -Hemoglobin -Hemoglobin modifications -Oxygen-hemoglobin dissociation curve -Oxygen content of blood

1
Q

What are the components of Hemoglobin?

A

Hemoglobin (Hb) is composed of 4 polypeptide subunits (2 alpa and 2 beta)

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2
Q

How many forms of (normal adult) Hemoglobin are there, what are they, and what distinguishes/defines each?

A

Exists in 2 forms: (1) T (taut) form has low affinity for O2 (2) R (relaxed) form has high affinity for O2.

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3
Q

What kind of cooperativity and allostery does Hb exhibit?

A

Hb exhibits positive cooperativity and negative allostery.

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4
Q

What 5 conditions favor taut over relaxed form of Hb? What effects does this have?

A

Increased (1) Cl- (2) H+ (3) CO2 (4) 2,3-BPG and (5) temperature favor taut form over relaxed form (shifts dissociation curve to right, leading to increased O2 unloading)

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5
Q

Where are the taut versus relaxed forms of Hb found in the body?

A

Taut in Tissues, Relaxed in Respiratory Tract

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6
Q

How does Fetal Hb differ from adult Hb in terms of structure?

A

Fetal Hb (2 alpha and 2 gamma subunits); (adult) Hemoglobin (Hb) is composed of 4 polypeptide subunits (2 alpa and 2 beta)

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7
Q

How does Fetal Hb differ from adult Hb in terms of affinity?

A

Fetal Hb (2 alpha and 2 gamma subunits) has lower affinity for 2,3-BPG than adult Hb and thus has higher affinity for O2

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8
Q

In general, what is the effect of hemoglobin modifications?

A

Lead to tissue hypoxia from decreased saturation and decreased O2 content

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9
Q

What is Methemoglobinemia? What distinguishes it from normal hemoglobin in terms of function?

A

Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has increased affinity for cyanide

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10
Q

What is the normal state of iron in Hb?

A

Iron in Hb is normally in a reduced state (ferrous, Fe2+); Think: “just the 2 of US: ferroUS is Fe2+”

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11
Q

What are 2 ways that Methemoglobinemia may present?

A

Methemoglobinemia may present with cyanosis and chocolate-colored blood

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12
Q

How is cyanide poisoning treated, and why?

A

To treat cyanide poisoning, use nitrites to oxidize Hb to methemoglobin, which binds cyanide. Use thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted.

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13
Q

How can Methemoglobinemia be treated?

A

Methemoglobinemia can be treated with methylene blue.

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14
Q

How do nitrites cause poisoning?

A

Nitrites cause poisoning by oxidizing Fe2+ to Fe3+

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15
Q

What is Carboxyhemoglobin? What distinguishes it from normal hemoglobin in terms of function?

A

Form of Hb bound to CO in place of O2. Causes decreased oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve. Decreased O2 unloading in tissues.

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16
Q

What change does Carboxyhemoglobin cause to the oxygen-hemoglobin dissociation curve? What change does it have in the tissues?

A

Causes decreased oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve. Decreased O2 unloading in tissues.

17
Q

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

A

Sigmoidal shape due to positive cooperativity (i.e., tetrameric Hb molecule can bind O2 molecules and has higher affinity for each subsequent O2 molecule bound).

18
Q

How does the oxygen-myoglobin dissociation curve differ from the oxygen-hemoglobin one?

A

Myoglobin is monomeric and thus does not show positive cooperativity; curve lacks sigmoidal appearance

19
Q

What occurs with a shift to the right on the oxygen-hemoglobin dissociation curve?

A

When curve shifts to the right, decrease affinity of Hb for O2 (facilitates unloading of O2 to tissue).

20
Q

What factors cause shifts of the oxygen-hemoglobin dissociation curve, and what conditions cause which shifts?

A

Think: “BAT ACE: BPG (2,3-BPG), Altitude, Temperature, Acid, CO2, Exercise; An increase in all factors (including H+) causes a shift of the curve to the right; A decrease in all factors causes a shift of the curve to the left

21
Q

What shift on the oxygen-hemoglobin dissociation curve does Fetal Hb cause, and why?

A

Fetal Hb has a higher affinity for O2 than adult Hb, so its dissociation curve is shifted left.

22
Q

Graph the oxygen-hemoglobin dissociation curve, including myoglobin and normal blood curves. On the normal blood curve, label oxygenated blood leaving the lungs versus blood returning from tissues.

A

See p. 598 in First Aid 2014 for first graph

23
Q

Graph normal blood versus 50% CO Hb in terms of pCO2 in mmHg (x axis) and O2 bound to Hb in mL O2/100 mL (y axis).

A

See p. 598 in First Aid 2014 for second graph

24
Q

Define O2 content.

A

O2 content = (O2 binding capacity x % saturation) + dissolved O2

25
Q

How much O2 can 1 g of Hb normally bind?

A

Normally 1 g Hb can bind 1.34 mL O2

26
Q

What is the normal Hb amount in blood?

A

Normal Hb amount in blood is 15 g/dL

27
Q

Under what condition does cyanosis result?

A

Cyanosis results when deoxygenated Hb > 5 g/dL

28
Q

What is the typical value for O2 binding capacity?

A

O2 binding capacity ~ 20.1 mL O2/dL

29
Q

Which of the following factors decrease as Hb falls: O2 content of arterial blood, O2 saturation, arterial PO2.

A

O2 content of arterial blood decreases as Hb falls, but O2 saturation and arterial PO2 do not

30
Q

What is the equation for O2 delivery to tissues?

A

O2 delivery to tissues = cardiac output x O2 content of blood

31
Q

What changes (if any) to the following measurements occur with CO poisoning: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?

A

(1) Normal (2) Decreased (CO competes with O2) (3) Normal (4) Decreased

32
Q

What changes (if any) to the following measurements occur with Anemia: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?

A

(1) Decreased (2) Normal (3) Normal (4) Decreased

33
Q

What changes (if any) to the following measurements occur with Polycythemia: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?

A

(1) Increased (2) Normal (3) Normal (4) Increased