Respiratory lecture #3 Flashcards Preview

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Flashcards in Respiratory lecture #3 Deck (37)
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1
Q

What kind of gas can diffuse?

A

dissolved gas

2
Q

T/F O2 is fairly insoluble in water

A

True

3
Q

Since less than 2% of oxygen in the blood is dissolved and can therefore diffuse, what is so important for oxygen diffusion and transport?

A

hemoglobin. Oxygen bound to hemoglobin accounts for 98% of the oxygen in the blood

4
Q

How many hemoglobin molecules are there per red blood cell?

A

about 250 million or 250,000,000- this is the same number of one dollar bills Taylor Swift has.

5
Q

You enjoyed that last little fun fact didn’t you. Describe hemoglobin to me or to yourself or to your wife or kid who really isn’t listening to your dental school babble.

A

Hemoglobin is a tetrameric molecule- it has 4 protein subunits, each with a heme group that includes 1 iron atom that can reversibly bind O2

6
Q

So, with your incredible hemoglobin knowledge, how many O2 molecules can a single red blood cell bind?

A

Well, if each heme subunit can bind an O2, that means there can be 4 O2 molecules per heme molecule. If a red blood cell has 250 million hemoglobin molecules, then there can be 1 billion oxygen molecules per red blood cell.

7
Q

T/F each hemoglobin molecule has 4 subunits and each subunit can bind one O2 molecule?

A

True

8
Q

Carrying capacity is also called saturation and its maximum is achieved when what happens?

A

When the percent saturation is the same as the percent of hemoglobin in HbO2

9
Q

The toal O2 in the blood is a function of what and what?

A

the partial pressure of O2 and the amount of Hb (hemoglobin) in the blood

10
Q

T/F binding of the O2 to Hb changes the conformation of the O2, but not the Hb molecule?

A

False- its the other way around. Binding of O2 changes the confirmation of the Hb but not the O2

11
Q

Can other things bind the Hb molecules? What does this mean?

A

Indeed they can. Some can have adverse affects on the affinity of O2 to Hb.

12
Q

T/F only dissolved O2 can diffuse into the tissues?

A

Truth!

13
Q

How does O2 bound to Hb get into the tissues?

A

Well, while it’s bound to the hemoglobin it can’t diffuse into the tissues. So as other dissolved oxygen diffuses out of the blood, the hemoglobin c an dump their bound oxygen into the dissolved pool as the partial pressure of O2 decreases. Then it can diffuse into the tissues

14
Q

Where does O2 go as it’s trying to get from the alveolus to the hemoglobin?

A

It diffuses across the respiratory surface into the plasma. Then it heads across the plasma membrane of the erythrocyte in order to bind Hb. Hb uptake of O2 maintains the PO2 gradient until Hb is saturated

15
Q

Where is the final resting place of the inhaled oxygen?

A

The mitochondria.

16
Q

What happens to the saturation curve of oxygen and hemoglobin if the infinity of Hb for O2 is increased?

A

The curve is shifted to the left and Hb gets fully saturated at a lower PO2
The opposite is true as well.

17
Q

What factors decrease Hb affinity for oxygen?

A

Increased temperature due to the production of metabolic heat
Increase in acidity
Increased 2,3 DPG activity

18
Q

What would increased acidity or increased 2,3 DPG activity decrease Hb affinity for oxygen?

A

Increased acidity means the presence of more H+. H+ can allosterically inhibit Hb so it can’t bind oxygen as much or as well.
2,3 DPG is responsible for allosteric modulation as well, except this modulation comes in the form of enhancing offloading/dissociation of oxygen from Hb

19
Q

What effect would exercising have on hemoglobin’s affinity for O2?

A

Exercising muscle is warm, produces acid, and produces a lot of DPG. It basically makes the Hb suck at its job.

20
Q

What are the normal arterial values of Hb and oxygen per 100ml of arterial blood?

A

15 g Hb

20 ml of O2

21
Q

What is anemia and what does it do to hemoglobin and oxygen saturation?

A

Anemia is when you have fewer RBC’s (can be due to reduced hematopoiesis or blood loss).
Anemia doesn’t change the partial pressure of oxygen, but it decreases how much Hb there is per ml of blood because there are fewer erythrocytes. Total oxygen content is reduced

22
Q

Tell me about carbon monoxide poisoning.

A

This happens when CO replaces O2 on the hemoglobin. CO competes for binding sites on Hb.
This is bad news because Hb affinity for CO is 200X greater than it is for Oxygen. Ouch. This doesn’t change the arterial partial pressure of oxygen or Hb, but the total amount of oxygen in the blood is reduced.

23
Q

Let’s talk about CO2. What are the three forms it’s transported in?

A

Dissolved (7%)
Bound to Hb (23%)
As HCO3 (70%)

24
Q

T/F CO2 is more soluble in plasma than O2?

A

True

25
Q

T/F as with O2, the dissolved pool represented what can diffuse in and out of capillaries?

A

True

26
Q

Where does CO2 bind on hemoglobin and where does O2 bind? What does this mean?

A

CO2 binds on the globin portion of hemoglobin.
O2 binds the iron molecule in each subunit of hemoglobin
This means that there is no direct competition between O2 and CO2

27
Q

If the partial pressure of CO2 goes up, what happens to Hb affinity for CO2?
What about if the partial pressure of oxygen decreases?

A

If the partial pressure of CO2 goes up then affinity of Hb for CO2 increases
If the partial pressure of oxygen decreases, the affinity of Hb for CO2 increases as well. So if there’s more CO2 or less O2, Hb like hanging out with CO2 even more.

28
Q

What happens to CO2 in water?

A

Carbonic acid and a hydrogen ion are formed (HCO3- and H+)`

29
Q

What is the enzyme that catalyzes the formation of carbonic acid?

A

Carbonic anhydrase (CA)

30
Q

What is the consequence of the action of carbonic anhydrase?

A

It acidifies the plasma, which decreases Hb’s affinity for O2

31
Q

How does CO2 get into the tissues?

A

Dissolved CO2 diffuses into the plasm and then into the erythrocyte. The some binds to Hb. Some is converted to bicarbonate, which is transported into the plasma..

32
Q

How is CO2 exchanged at the pulmonary capillaries?

A

Dissolved CO2 diffuses into the alveoli, which decreases the partial pressure of CO2. Hb unloads CO2 and loads O2

33
Q

In the pulmonary capillaries, what maintains the CO2 gradient into the alveolar air?

A

The carbonic acid reaction is reversed, taking HCO3 and turning it into CO2, maintaining the gradient that gets the CO2 into the alveolar air.

34
Q

How is H+ transported on Hb?

A

H+ binds to histidine residues on Hb. In the tissues, Hb picks up H+, which minimizes the effect of HCO3- on pH.
In the lungs, Hb releases H+ so it can combine with HCO3- via the reverse mechanic mom carbonic anhydrase (CA).

35
Q

T/F Hb buffers most of the H+ produced by the carbonic anhydrase (CA) reaction?

A

True

36
Q

What is respiratory acidosis?

A

It is when the respiratory rate is lower the normal or hypoventilation results in increases of the partial pressure of CO2 and H+

37
Q

What is respiratory alkalosis?

A

It is when the respiratory rate is faster than normal (hyperventilation) which results in decreases in H+ and the partial pressure of CO2. That’s why you hyperventilate before holding your breath for a long time.