Oxygen Transport in Blood

Question 1

What is Dalton’s Law of partial pressure?

Answer 1

Each gas in a mixture of gases exerts a pressure that is proportional to its conc. and independent of other gases present

Question 2

What can partial pressure exerted by a single gas be calculated as?

Answer 2

PO2 = PB.FO2
In air PB = 760mmHg
FO2 = 0.21 (fraction of oxygen in the air)

Question 3

What is maximum partial pressure of water a function of?

Answer 3

Temperature
At 37 degrees = 47mmHg

Question 4

What is partial pressure of oxygen in a room with humidified air?

Answer 4

(760 - 47) X 0.21 = 149.7mmHg

Question 5

What does total amount of O2 in solution depend on?

Answer 5

Solubility of O2 in solution

Question 6

What is Henry’s Law?

Answer 6

Amount of gas dissolved in a solution is directly proportional to partial pressure of the gas in the solution
Conc gas = S.gas

Question 7

How is O2 transferred?

Answer 7

By passive diffusion

Question 8

What 3 things is the rate of gas transfer proportional to?

Answer 8

Tissue surface area
Difference in gas partial pressure between 2 sides
Diffusion constant (solubility)

Question 9

What is the rate of gas transfer inversely proportional to?

Answer 9

Tissue thickness

Question 10

What are the two ways oxygen can be transported?

Answer 10

Dissolved in physical solution - 3%
Bound to Haemoglobin - 97%

Question 11

What is dissolved O2 a linear function of?

Answer 11

PO2 (Henry’s Law)
0.003ml O2/100ml blood for each mmHg PO2

Question 12

What type of molecule is Heme?

Answer 12

Iron-porphyrin compound

Question 13

Describe structure of Heme?

Answer 13

Joined to protein globin
Tetramer with 4 polypeptide chains - 2 alpha and 2 beta
4 haem groups, each bound to alpha or beta

Question 14

What does each haem group contain?

Answer 14

Porphyrin ring and a ferrous atom (Fe++) - bind reversibly with O2

Question 15

What bonds do deoxyHb globin chains have?

Answer 15

Electrostatic bonds in T conformation = low O2 affinity

Question 16

What does binding of O2 to deoxyHb cause?

Answer 16

Breaks bonds - exposes O2 binding sites - relaxed conformation

Question 17

What does R conformation have?

Answer 17

High affinity for O2

Question 18

What is unique to Hb F (foetal)?

Answer 18

Profound oxygen affinity

Question 19

What is the difference in Hb S (Sickle cell anemia)?

Answer 19

Valine instead of glutamic acid in beta chains - low oxygen affinity

Question 20

What is the haemoglobin type for a normal adult?

Answer 20

Hb A

Question 21

What 4 things affect the affinity of haemoglobin for oxygen?

Answer 21

pH, PCO2, 2,3DPG and temperature

Question 22

What causes the oxygen-dissociation curve to shift left?

Answer 22

Decreased temp, 2,3-DPG H+
CO
Drop in saturation

Question 23

What causes the oxygen-dissociation curve to shift to the right?

Answer 23

Increased temp, 2,3-DPG and increased H+
Reduced affinity at cellular level

Question 24

What happens when Hb has a greater affinity for CO2?

Answer 24

Causes O2 to be released from haemoglobin

Question 25

What does CO cause?

Answer 25

Reduces the oxygen carrying capacity of blood

Question 26

Define oxygen capacity.

Answer 26

Max. amount of O2 that can be combined with Hb
1.39 ml O2/g Hb - 15g of Hb/100ml in normal blood

Question 27

What is O2 saturation of Hb given by?

Answer 27

(O2 combined with Hb/ O2 capacity) X 100

Question 28

What causes anaemia?

Answer 28

Reduced Hb - less than 15g/100ml of blood