Module 22 gas diffusion

Question 1

Where is oxygen most concentrated?

Answer 1

In the atmosphere (21%). Remember that gas flows down it’s concentration gradient all the way to our tissues!

Question 2

What is partial pressure?

Answer 2

A measure of gas concentration in context of the whole environment. Or the proportion of total pressure due to the presence of one specific gas in the mixture.

Question 3

160 mmHg / 760 mm Hg

Answer 3

The partial pressure of oxygen in the atmosphere

Question 4

How do gas molecules move?

Answer 4

From high partial pressure to low partial pressure.

Question 5

How is partial pressure different than bulk flow?

Answer 5

Bulk flow refers to overall movement of air but partial pressure refers to the movement of gas molecules.

Question 6

What is the PO2 and PCO2 in the alveoli?

Answer 6

100 mmHg (O2)
40 mmHg (CO2)

Question 7

What is the PO2 and PCO2 in the arterial blood?

Answer 7

100 mmHg (O2)
40 mmHg (CO2)

Question 8

What is the PO2 and PCO2 in the venous blood?

Answer 8

Equal to or less than 40 mmHg (O2)
Equal to or less than 46 mmHg (CO2)

Question 9

What is the PO2 and PCO2 in the venous blood at normally active tissues?

Answer 9

PO2 is equal to or less than 40 mmHg
PCO2 is equal to or less than 46 mmHg

Question 10

How does gas exchange occur from lungs to bloodstream to tissues?

Answer 10

Oxygen concentrations are always lowest in the tissues so oxygen flows down the concentration gradient from lungs, to veins, to tissues. Carbon dioxide concentrations are higher in tissues, then veins, then alveoli.

Question 11

Hyperventilation

Answer 11

when ventilation exceeds the demands of the tissues

Question 12

Hypoventilation

Answer 12

Ventilation is low; insufficient enough to keep up with oxygen demands of tissue.

Question 13

Hemoglobin

Answer 13

A 4 sub-unit protein consisting of iron that allows oxygen to bind to it. Found in RBC

Question 14

% Hemoglobin (Hb) saturation

Answer 14

(O2 bound to Hb/Total O2 binding sites) * 100

Question 15

Where is hemoglobin saturation the highest and where is it the lowest in the vessels?

Answer 15

98.5% hemoglobin saturation in the arterial blood

75% hemoglobin saturation in the venous blood (“deoxygenated”)

Question 16

What is hemoglobin saturation after giving up oxygen to normal tissues?

Answer 16

75% and PO2 was at 40 mmHg

Question 17

When muscles are active during exercise the partial pressure of oxygen CAN decrease to 20 mmHg. So hb saturation is 35%

Answer 17

True

Question 18

Hemoglobin affinity shifts right

Answer 18

This means there is lower affinity for oxygen. Occurs during times of excercise. Temperature increases and pH decreases.

Question 19

Hemoglobin affinity shifts to the left.

Answer 19

Higher affinity for oxygen

Question 20

Myoglobin a protein found in muscles has a higher affinity for oxygen than hemoglobin?

Answer 20

True

Question 21

What percentage of CO2 is dissolved in the blood?

Answer 21

5-6%

Question 22

What percentage of carbon dioxide is bound to hemoglobin?

Answer 22

5-8%

Question 23

Red blood cells (RBC) express an enzyme called carbonic anhydrase (CA), which catalyzes the reaction of CO2 –> bicarbonate (it also catalyzes the reverse reaction).

Answer 23

True!

Question 24

RBC convert CO2 to bicarbonate

Answer 24

true

Question 25

Bicarbonate exits the RBC’s and travels in the bloodstream

Answer 25

true

Question 26

Bicarbonate is converted back into CO2 by a RBC in a lung capillary and then breathed out in the alveoli?

Answer 26

True

Question 27

Tissues move over bicarbonate?

Answer 27

False they move over carbon dioxide to the RBC. RBC converts it to bicarbonate.

Question 28

Hemoglobin affinity for oxygen increases when it’s cold?

Answer 28

True, the curve shifts to the left. Less oxygen is releases to tissues.