3.2.7 transport of oxygen

Question 1

affinity

Answer 1

strong attraction

Question 2

dissociation

Answer 2

releasing oxygen from oxyhaemoglobin

Question 3

fetal haemoglobin

Answer 3

type of haemoglobin usually only found in foetus

Question 4

haemoglobin

Answer 4

red pigment used to transport oxygen in blood

Question 5

erythrocytes

Answer 5

red blood cells

Question 6

describe the structure of haemoglobin

Answer 6

• complex protein with 4 subunits
• each subunit = polypeptide chain & haem group
• haem group contains single iron ion (Fe2+)
• iron ion attracts/holds single oxygen molecule (high affinity for oxygen)
• haemoglobin molecule only carry 4 oxygen molecules

Question 7

describe the reversible binding of oxygen by haemoglobin

Answer 7

• association (binding) of haemoglobin & oxygen occurs in lungs where partial pressure (concentration) of oxygen is high
• dissociation of haemoglobin & oxygen occurs in tissues where partial pressure (concentration) of oxygen is low

Question 8

describe the transport of oxygen in lungs to tissues

Answer 8

1. oxygen absorbed into blood as passes alveoli (lungs)
2. oxygen molecules diffusing into blood plasma diffuse into RBC
3. in RBC, oxygen becomes associated with haemoglobin (oxygen binds reversibly)
4. takes oxygen molecules out of solution = high concentration gradient in lungs
5. blood carries oxygen from lungs to heart & travels around body to tissues
6. in tissues, cells require oxygen for aerobic respiration = oxyhaemoglobin release oxygen via dissociation

Question 9

another name for partial pressure of oxygen (pO2)

Answer 9

oxygen tension

Question 10

what is partial pressure of oxygen (pO2) measured in

Answer 10

kPa

Question 11

describe the haemoglobin dissociation curve
3 steps - 1) low oxygen tension, 2) oxygen tension increases & 3) haemoglobin approaches 100% saturation

Answer 11

• haemoglobin associates with oxygen to produce s-shaped curve

1. low oxygen tension = haemoglobin doesn’t readily associate its oxygen molecules as haemoglobin groups at centre of haemoglobin = oxygen cannot easily reach haem group & associate = low saturation level of haemoglobin
2. oxygen tension increases = diffusion gradient into haemoglobin increases = 1 oxygen molecule enter & associates with 1 haem group = slight change in haemoglobin molecule (conformational change) = allows more oxygen molecules to enter haemoglobin molecule & associate with other haem groups = steepness of curve
3. haemoglobin approaches 100% saturation = curve levels off causing s-shaped curve

Question 12

compare adult & fetal haemoglobin (dissociation curves)

Answer 12

• fetal haemoglobin has higher affinity for oxygen = haemoglobin dissociation curve for fetal haemoglobin is to left of adult haemoglobin

why?
—> fetal haemoglobin must associate with oxygen in environment where oxygen tension is low enough to make adult haemoglobin dissociate
–> in placenta (oxygen tension is low), fetal haemoglobin will absorb oxygen from surrounding fluid = reduces oxygen tension further
–> as a result, oxygen diffuses from mother’s blood fluid into placenta = reduces oxygen tension within mothers blood
–> causes maternal haemoglobin to dissociate further