Gas Transport

Question 1

what do respiratory and circulatory systems function together to transport?

Answer 1

CO2 from tissues to lungs and O2 from lungs to tissues

Question 2

what are the anatomical and physiological properties of the respiratory and circulatory systems which facilitate gas diffusion?

Answer 2

large surface area for gas exchange, large partial pressure gradients, gases with advantageous diffusion properties, specialised mechanisms for transporting O2 and CO2 between lungs and tissues

Question 3

what is partial pressure?

Answer 3

fraction of gas in gas mixture x barometric pressure

Question 4

what are the two forms that oxygen is transported in?

Answer 4

dissolved and bound to haemoglobin

Question 5

how is dissolved O2 in the blood measured?

Answer 5

in an arterial blood sample

Question 6

what is the amount of O2 dissolved in the blood proportional to?

Answer 6

the partial pressure

Question 7

why is transport of O2 in dissolved form not adequate?

Answer 7

because during exercise the CO is 30L/min but the arterial blood contains 3ml O3/litre of blood so that would only be 90ml/min of O2 to tissues BUT tissue requirements may need 3000ml O2/min

Question 8

what is haemoglobin?

Answer 8

major transport molecule for O2 found in red blood cells

Question 9

what is the functional unit of haemoglobin?

Answer 9

4 haem groups joined to globin protein

Question 10

what is the site of O2 binding?

Answer 10

iron in the reduced ferrous form (Fe+++)

Question 11

what does the oxyhaemoglobin dissociation curve illustrate?

Answer 11

the relationship between PO2 in blood and the number of O2 molecules bound to Hb

Question 12

what does the flat portion of the oxyhaemoglobin curve represent?

Answer 12

drop in PO2 from 100 to 60mmHg has minimal effect on Hb saturation

Question 13

what does the steep portion of the oxyhaemoglobin curve represent?

Answer 13

large amount of O2 is released from Hb with only small change in PO2, facilitating release into tissues

Question 14

how many O2 atoms can a Hb molecule bind to?

Answer 14

4

Question 15

what is O2 saturation?

Answer 15

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

Question 16

what does 100% saturation mean?

Answer 16

all haem groups of Hb molecules fully saturated with O2

Question 17

what is used in clinic to measure O2 saturation?

Answer 17

pulse oximeters

Question 18

how does a pulse oximeter measure O2 saturation?

Answer 18

measures ratio of absorption of red and infrared light by oxyHb and deoxyHb

Question 19

in normal healthy conditions what is the volume of CO2 produced per minute?

Answer 19

200ml/min, 80 molecules CO2 expired by lung for every 100 molecules O2 that enter

Question 20

what is the respiratory exchange ratio?

Answer 20

CO2 expired to O2 uptake

Question 21

what are the 3 forms of CO2 transport?

Answer 21

dissolved, bound to haemoglobin and as bicarbonate

Question 22

what is the direction and speed of the carbon dioxide- bicarbonate reaction determined by?

Answer 22

the concentration gradients

Question 23

what is the direction of the bicarbonate reaction in systemic capillaries?

Answer 23

rightwards (bicarbonate - carbon dioxide) CO2 produced by tissues is expelled into blood

Question 24

what is the direction of the bicarbonate reaction in pulmonary capillaries?

Answer 24

leftwards (carbon dioxide - bicarbonate) CO2 to be expelled into alveoli

Question 25

what can changes in the bicarbonate concentration be used to do?

Answer 25

stabilise the pH

Question 26

how can acidity in the blood be regulated?

Answer 26

by using ventilation to adjust the PCO2 or by using the kidneys to regulate the bicarbonate concentration

Question 27

what is the main point of the O2 dissociation curve?

Answer 27

above 60mmHg the increase of decreased PO2 has minimal effect on Hb saturation

Question 28

what is the major transport system for O2?

Answer 28

within red blood cells bound to Hb

Question 29

what is the major transport system for CO2?

Answer 29

within red blood cells in the form of bicarbonate

Question 30

what does the carbon dioxide - bicarbonate pathway play a critical role in?

Answer 30

regulation of H+ ions and in maintaining acid-base balance in body