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Block 2 Exam 3 > Cremo 3: Hemoglobin and blood gas transport > Flashcards

Cremo 3: Hemoglobin and blood gas transport Flashcards

1
Q

O2 sensing mechanism of Hb

A

O2 binds to Fe2+ and affects the degree to which Fe2+ is in the plane of the ring. The movement drags the His side chain with it and Hb can sense this shift.

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2
Q

How do RBCs take care of Hb?

A
  1. protects it from proteases

2. protects it from oxidizing environment of plasma

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3
Q

How does Hb take care of heme?

A

Hb has hydrophobic binding sites that keep heme soluble.

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4
Q

How does Hb-protoporphyrin-IX take care of Fe2+?

A

Protects fe2+ from oxidation to fe3+

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5
Q

How does Fe2+ take care of O2?

A

Provides for reversible binding of O2 and transport

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6
Q

2 functional reasons for Hb

A
  1. prevents Fe2+ from irreversible oxidation to Fe3+

2. allows for reversible binding of O2 to Fe2+

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7
Q

As you add O2 to Hb, it becomes easier to bind the O2. Why is this so?

A

Some salt links have already been broken!

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8
Q

How do you find SaO2?

A

(HbO2/Hb+HbO2) * 100

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9
Q

What does a lower P50 indicate?

A

Tighter binding affinity of O2 for Hb

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10
Q

Normal P50 for HbA

A

27mmHg

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11
Q

From lungs to tissues, about what percent of O2 binding sites have dumped their O2?

A

18%

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12
Q

If there is hypoxia, RBCs can dump up to (blank)% of their oxygen to the tissues that need it most.

A

63%

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13
Q

Things that can shift the Hb-O2 dissociation curve to the right?

A

pH, CO2, temperature, BPG

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14
Q

Things that cause weaker binding of O2 to Hb (right shift)

A

Hot, sweating, gasping

  1. increased temp
  2. increased [H+], lower pH
  3. increased PaCO2
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15
Q

How does increased H+ weaken O2 binding?

A

H+ stabilizes the salt bridges that need to be broken for O2 to bind!

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16
Q

H+ and O2 do not like to bind at the same time. So what does decreased pH (more H+) cause?

A

Decreasing pH forces Hb to dump some O2 to tissues. This is helpful under acidic conditions, because tissues need more oxygen!

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17
Q

How does CO2 weaken O2 binding to Hb?

A

Favors formation of carbamate, which stabilizes salt bridges that must be broken for O2 to bind.

18
Q

So, what are the two things that do not like to bind with O2?

A

H+ and CO2

19
Q

(Bohr/Haldane) says that CO2/H+ weakens O2 binding to Hb. (Bohr/Haldane) says O2 weakens CO2/H+ binding to Hb.

A

Bohr; Haldane

20
Q

How does BPG weaken O2 binding to Hb?

A

Binds in the central hole in Hb. O2 and BPG do not like to bind to Hb at the same time. So, this causes chronic hypoxia.

21
Q

What three things increase at high altitude?

A
  1. number of RBCs
  2. [Hb]
  3. [BPG]
22
Q

What are the three pathways that describe carbohydrate metabolism in the RBC?

A
  1. Glycolysis
  2. 2,3-BPG metabolism
  3. Pentose phosphate shunt
23
Q

Fetal hemoglobin has a (blank) affinity for oxygen, and causes a (blank) shift in the O2 curve.

A

Higher; left

24
Q

Main compound that we talked about that can compete with O2 at heme binding site?

A

CO – CO binds 200 times more tightly to heme than O2.

25
Q

CO decreases maximal O2 binding capacity, so at high [CO] patient can be hypoxic while maintaining a normal (blank)

A

PaO2

26
Q

An altered state of hemoglobin in which the ferrous (2+) form of heme
is oxidized to the ferric form (3+) thus making the heme moiety unable to bind oxygen

A

Methemoglobin

27
Q

What does a pulse ox measure?

A

SaO2

28
Q

What is the equation for total O2 content? What variable in the eq is reported by PaO2 and which is not?

A

CaO2 = Hb · 1.34 · SaO2/100
Total O2 content = CaO2 = O2(dissolved) + O2(bound to Hb)
O2 dissolved is reported by PaO2, but O2(bound to Hb) is not!

29
Q

Is there more O2 bound to Hb or freely dissolved?

A

Much more bound to Hb. Ex: 20ml bound, 0.48ml free

30
Q

So what is the main difference between PaO2 and CaO2?

A

PaO2 represents only dissolved O2 content, and does not account for O2 bound to Hb. CaO2 includes all O2 present!

31
Q

What is a normal CaO2?

A

20!

32
Q

Which value is most useful? PaO2 or CaO2?

A

CaO2! A patient can have a normal PaO2 and be starved of O2!

33
Q

Impaired O2 delivery to the tissues

A

Hypoxia

34
Q

Low CaO2 (oxygen content) caused by reduction in PaO2, SaO2, or [Hb]

A

Hypoxemia

35
Q

3 causes of hypoxia

A
  1. Hypoxemia: reduced PaO2, SaO2, or [Hb]
  2. Reduced O2 delivery to the tissues
  3. Decreased tissue O2 uptake
36
Q

PCO2 equation

A

PaCO2 = VCO2 * 0.863 / VE – VD

37
Q

Henderson-Hasselbalch equation

A

pH = 6.1 + log [HCO3-]/0.03*PaCO2

38
Q

Alveolar gas equation

A

PAO2 = PIO2 – 1.2(PaCO2)

39
Q

A-a difference equation

A

P(A-a)O2 = PAO2 – PaO2

40
Q

Oxygen content equation (CaO2)

A

CaO2 = Hb · 1.34 · SaO2

Block 2 Exam 3 (19 decks)

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