Respiration - Gas Transport

Question 1

Describe the pulmonary circuit

Answer 1

O2 enters the blood, CO2 leaves

Question 2

What is the systemic circuit

Answer 2

O2 leaves the blood, CO2 enters the blood

Question 3

Describe the gas concentration gradient in the pulmonary capillary

Answer 3

PO2 100(alveolar air) > 40 (venous blood)
PCO2 40 (alveolar air) < 47 (venous blood)

Question 4

What are the anatomical and physiological properties to facilitate gas diffusion

Answer 4

1) large surface area for gas exchange
2) large partial pressure gradients
3) gases with advantageous diffusion properties
4) specialised mechanisms for transporting O2 and CO2 between lungs and tissues

Question 5

What is partial pressure

Answer 5

Concentration of a particular gas within a mixture of gases

Question 6

What ways are oxygen transported

Answer 6

1) dissolved
2) bound to haemoglobin (Hb)

Question 7

Describe dissolved oxygen

Answer 7

Only a small percentage of O2 in blood is dissolved in the dissolved form, the amount is proportional to its partial pressure, for each mmHg PO2 there is 0.003ml O2/100ml of blood

Question 8

How much oxygen is dissolved on average in atrial blood

Answer 8

Arterial blood (PaO2) = 100mmHg, contains 0.3ml O2/100ml blood

Question 9

Is dissolved oxygen in the blood enough to meet the body’s oxygen requirements

Answer 9

No

Question 10

What is the average cardiac output at rest

Answer 10

5L/min

Question 11

What are the oxygen requirements at rest

Answer 11

250ml O2/min

Question 12

What is the oxygen requirements during strenuous exercise

Answer 12

3000ml O2/min

Question 13

What molecule transports oxygen

Answer 13

Haemoglobbin

Question 14

Describe the structure of haemoglobbin

Answer 14

Four haem groups joined to a globin protein (2 alpha chains, 2 beta chains)

Question 15

Where does oxygen bind on haemoglobbin

Answer 15

To the iron molecules in the haem groups, one haemoglobbin can transport 4 oxygen molecules

Question 16

What many haemoglobbin molecules per red blood cell on average

Answer 16

280 million Hb molecules/red blood cell

Question 17

Describe how haemoglobin works so efficiently

Answer 17

Binding and dissociation of O2 with Hb occurs in milliseconds to facilitate transport which is necessary because red blood cells are in capillaries for one second only

Question 18

What two things can impact the binding of oxygen to haemoglobin

Answer 18

• temperature
• pH

Question 19

Is oxygen binding to Hb reversible

Answer 19

Yes

Question 20

What is the average partial pressure of oxygen PO2 in the blood

Answer 20

The partial pressure of oxygen in the blood is 100mmHg

Question 21

Describe what happens to oxygen and Hb saturation when partial pressure drops

Answer 21

You can withstand a drop from about 100 to 60 in partial pressure without the haemoglobin mechanism being majorly affected

Question 22

What happens when the partial pressure of oxygen drops below 60

Answer 22

The partial pressure of oxygen in the blood is quite low, which means there isn’t enough oxygen being transported around the body, not all the Hb molecules are saturated

Question 23

What is the oxygen carrying capacity of haemoglobin

Answer 23

211mls O2/1L of blood

Better than oxygen being dissolved in the blood

Question 24

What does oxygen saturation refer to

Answer 24

Refers to the amount of O2 bound to Hb relative to maximal amount that can bind

Question 25

How is oxygen saturation measured

Answer 25

Using a pulse oximeter, this measures the ratio of absorption of red and infrared light by oxyHb and deoxyHb

Basically measures how much oxygen is bound to Hb

Question 26

What is the normal amount of CO2 expired per minute

Answer 26

200ml CO2 / min produced

Question 27

What is the Normal respiratory exchange ratio

Answer 27

80 molecules CO2 expired for every 100 molecules O2 entering

0.8 in normal adults

Question 28

How is CO2 carried around the blood

Answer 28

1) 7% will remain dissolved in the blood plasma
2) 23% bound to haemoglobin (Hb)
3) 70% converted to bicarbonate

Question 29

What happens to the majority of carbon dioxide in the blood

Answer 29

Converted to bicarbonate, which can alter the pH of the blood

Question 30

Bicarbonate is converted into water and carbon dioxide by what

Answer 30

Pulmonary capillaries

Question 31

Bicarbonate is converted into H+ and HCO3- by what

Answer 31

Systemic capillaries

Question 32

Why is the majority of CO2 in the blood converted into bicarbonate

Answer 32

To maintain the acid base of the blood

Question 33

Henderson hasslebach equation for respiration

Answer 33

Pk = log (HCO3)/Pco2*sol