4.5 Transport of Gases in Blood

Question 1

describe the structure of erythrocytes and how it is adapted for gas exchange

Answer 1

biconcave shape - maximises surface area for gas exchange
small + flexible - allows easier movement through narrow capillaries
no nucleus - more room to carry respiratory gases
packing with haemoglobin

Question 2

what is haemoglobin made up of?

Answer 2

4 globular proteins

1 iron ion

Question 3

give a property of haemoglobin

Answer 3

it has an affinity for oxygen - can carry up to four oxygen molecules

Question 4

what is it called when haemoglobin becomes oxygenated?

give the equation

Answer 4

oxyhaemoglobin

Hb + 4O2 « Hb4O2

Question 5

define partial pressure of a gas

Answer 5

amount of gas present in a mixture

measured by the pressure it contributes to total pressure of gases

Question 6

describe how oxygen is transported in the lungs

Answer 6

oxygen diffuses into blood plasma
passes down a concentration gradient + into erythrocytes
oxygen binds to Hb to maintain the conc gradient
oxygen binds to Fe2+ group of Hb

Question 7

describe how oxygen is transported in the respiring tissue

Answer 7

oxygen dissociates from oxyhaemoglobin

oxygen can then diffuse out of the erythrocytes + to respiring cells

Question 8

what is pO2?

Answer 8

partial pressure for oxygen
amount of oxygen in tissue
measured in kPa

Question 9

what does it mean to have a high partial pressure for oxygen?

Answer 9

more oxygen molecules are able to associate with Hb molecules to be transported

Question 10

where is haemoglobin saturation the highest in the body?

Answer 10

in the lungs

Question 11

in respiring tissue, tje pO2 is low. what happens?

Answer 11

at low pO2, oxygen dissociates from oxyhaemoglobin + can diffuse to the respiring cells

Question 12

as pO2 increases, what happens to the saturation of Hb?

Answer 12

increases

Question 13

describe the process of oxygen associating with haemoglobin

Answer 13

after the first oxygen associates, the conformation of Hb changes
conformation change makes it easier for the 2nd and 3rd molecule to associate
it is difficult to associate a fourth oxygen because Hb becomes saturated (“full”)

Question 14

what do we mean by high affinity?

Answer 14

Hb binds more easily, even at low pO2

dissociates less readily

Question 15

what do we mean by low affinity?

Answer 15

Hb binds less readily
dissociates faster
oxygen is readily available for respiring tissue

Question 16

what is foetal haemoglobin?

Answer 16

red blood cells in the foetus contain a special form of Hb

Question 17

which has a high affinity for oxygen, adult or foetal Hb? explain why.

Answer 17

foetal Hb - helps to maimise oxygen uptake from mother’s blood, which has already lost some of its oxygen by the time it reaches placenta

Question 18

to get oxygen from maternal blood to foetal blood, what must happen ?

Answer 18

foetal Hb needs a stronger affinity for oxygen than maternal Hb

Question 19

give two features of foetal Hb

Answer 19

stronger oxygen affinity

becomes saturated at lower pO2

Question 20

describe what myglobin is

Answer 20

respiratory pigment found in muscles
small red protein
contains haem group which binds to oxygen

Question 21

give 3 features of myoglobin

Answer 21

higher affinity for oxygen than haemoglobin
becomes easily saturated with oxygen
not affected by pO2 in tissues

Question 22

what happens when myoglobin binds to an oxygen molecule?

Answer 22

it does not give up easily so acts as an oxygen store

when o2 levels in active muscles get low, and co2 levels are high, myoglobin releases its store of o2

Question 23

give differences in structure and affinity to o2 of haemoglobin and myoglobin

Answer 23

Hb-
tetramer- 4 polypeptide chains
supplies blood all over body
low affinity to o2 compared to Mb

Mb-
monomer- 1 polypeptide chain
supplies o2 to muscles
higher affinity to o2 compared to Hb

Question 24

what is the Bohr effect?

Answer 24

effect of co2 on oxygen dissociation on Hb curve

Question 25

at high carbon dioxide levels in tissues

Answer 25

Hb binds with O2 less well (low affinity) so releases more o2

Question 26

at low carbon dioxide levels in lungs

Answer 26

Hb binds with oxygen more easily (high affinity)