Exam #3: Transport of Oxygen & Carbon Dioxide Flashcards Preview

Medical Physiology > Exam #3: Transport of Oxygen & Carbon Dioxide > Flashcards

Flashcards in Exam #3: Transport of Oxygen & Carbon Dioxide Deck (29):
1

What is the difference between dissolved oxygen & conjugated oxygen?

Dissolved= Only dissolved gas generates partial pressure
(0.3%)

Conjugated= conjugated to Hb
(99.7% --reserve to draw from/ buffer)

2

Describe the structure of HbA.

2x alpha chains
2x Beta chains
4x Heme groups that can bind 1 O2

Thus HbA can bind 4 O2 molecules

3

Describe the structure of heme.

A prophyrin ring
Fe++ reversible binds O2

4

What is methemoglobin?

Fe+++ instead of Fe++ heme

DOES NOT bind O2

5

What causes an increase in methemoglobin?

1) Oxidation of Fe++ to Fe+++ by nitrites & sulfonamides
2) Deficiency is methemoglobin reductase

6

Describe the structure and function of Fetal Hb.

2x Beta chains are replaced by gamma chains

Higher affinity for O2 than HbA facilitates oxygen movement to the fetus

7

What is Hemoglobin S?

- Cause of sickle cell disease
- Abnormal beta subunits
- Forms sickle- shaped rods in RBCs that occlude small blood vessels
- Lower affinity for oxygen

8

What is the oxygen binding capacity?

The maximum oxygen volume that can combine with Hb, which is dependent on
- Hb concentration
- binding properties

9

What is the oxygen content? What is the equation for oxygen content?

Actual amount of O2 per volume of blood

O2 binding capacity x SaO2 + Dissolved O2

10

How is oxygen content altered in anemia?

Decreased Hb decreases oxygen content

11

What factors determine oxygen delivery to the tissues?

Cardiac ouput
Oxygen Content

= CO x Oxygen content

12

Draw the oxygen dissociation curve.

Hb saturation % vs. partial pressure of oxygen

13

What are the important features of the oxygen dissociation curve?

- Little change in Hb saturation at high partial pressures of oxygen (arterial) vs. large changes at low partial pressure (venous, 40 mmHg)
- Under normal conditions 5 mL of oxygen delivered
- Hb sets upper limit on the tissue partial pressure of oxygen
- Hb automatically delivers O2 to tissues at a tight PO2 range

14

What is the P50 value?

PO2 at which Hb is 50% saturated

15

What happens when the P50 is larger?

Shift the oxygen dissociation to the right

- Weaker binding
- Hb releases O2 eaeier

16

What happens when the P50 is smaller?

Shift the oxygen dissociation to the left

- Tighter binding
- Hb release O2 harder

17

How does an increase in temperature shift the oxygen dissociation curve?

Shift to the right
Easy delivery of oxygen

18

How does hypothermia change the oxygen dissociation curve?

Left shift
Preserve oxygen

19

How does a decreased in pH shift the oxygen dissociation curve? Give some examples. What is this called?

Right shift

-Acidosis
- DKA
- CKD

"Acid Bohr effect"

20

How does an increase in pH shift the oxygen dissociation curve?

Left shift

21

What is the Co2 Bohr effect? How does high CO2 affect the oxygen dissociation curve?

Binding of CO2 to Hb reduces the affinity of Hb for O2 (right shift in curve)

- High Co2 in tissue
- Makes Hb let go of O2 in the tissue

22

What is 2,3-diphosphoglycerate (2,3-BPG)? How does it affect the oxygen dissociation curve & when is it increased?

End product of RBC metabolism that is increased in:
- Hypoxia
- High altitude
- Anemia

Increased= right shift

23

How is the 2,3-BPG concentration altered in stored blood? What is the impact?

Decreased 2,3-BPG in stored blood products means that there is an increase in O2 affinity; this can lead to decreased tissue perfusion in blood replacement therapy

24

Describe the toxic effects of CO.

CO binds Hb with 250x affinity
- PaO2 is roughly normal= no feedback that content is low
- No physical sign of hypoxemia aside from bright cherry red skin

25

What are the symptoms of CO intoxication?

Altered reaction time
Blurred vision
Unconsciousness

26

List the three forms of CO2 in the blood and their relative concentrations.

1) 7% is dissolved CO2
2) 23% is conjugated to Hb
3) 70% is HCO3-

Thus, HCO3- (bicarbonate) is the main form of CO2 in the blood

27

What reaction is catalyzed by carbonic anhydrase?

Carbon dioxide and water to bicarbonate and protons

28

Draw the CO2 binding curve.

N/A

29

What is the Haldane effect?

Effect of oxygen on the CO2 equilibrium

- Higher PO2 will shift the CO2 equilibrium to the right
- Allows the blood to load more CO2 in the tissue and unload more at the lungs

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