Haemoglobin

Question 1

describe the transport of oxygen in large organisms

Answer 1

• a smaller surface area to volume ratio
  -so simple diffusion is not sufficient
• therefore organisms circulate blood around their bodies to carry oxygen to respiring tissues

Question 2

describe the structure of haemoglobin

Answer 2

• complex protein with a quaternary structure
• composed of 4 polypeptide subunits
  -each containing a HAEM group
• each haem (Fe2+ ) group can bind with one O2 molecule
• So four O2 molecules in total

Question 3

how many molecules of haemoglobin does an Erythrocyte (rbc) contain approx ?

Answer 3

approx. 300 million molecules

Question 4

when oxygen binds with haemoglobin, what is formed?

Answer 4

OXYHAEMOGLOBIN
in a reversible reaction but does not always bind to 4 molecules of O2

Question 5

What is saturation? and how do we calculate percentage saturation

Answer 5

the amount of oxygen combined is described in terms of percentage saturation which is ;
= oxygenated haemoglobin / maximum saturation x 100

Question 6

describe cooperative O2 loading :

Answer 6

• the 1st o2 molecule alters the tertiary structure of the Hb molecule
• this exposes the 2nd and 3rd o2 binding sites
• which is easier to bind and load

Question 7

what is the definition of partial pressure of oxygen (pO2 / kPa )

Answer 7

the proportion of oxygen in a mixture of gases or a solution
eg. higher pO2 > more oxygen loaded > haemoglobin is more saturated

Question 8

define loading/association , unloading/ dissociation , affinity.

Answer 8

loading: when oxygen is taken up my hb
unloading: when oxygen is released by hb
affinity: a natural attraction to something

Question 9

what shape is an oxygen dissociation curve?

Answer 9

S shaped - sigmoid curve
representing the cooperative nature of oxygen binding

Question 10

describe the pO2 in lungs

Answer 10

• pO2 is high in capillaries (about 13.16kPa)
• Hb has a higher affinity for O2 at a high pO2
• Hb becomes fully saturated as the RBC pass through the pulmonary capillaries in lungs
• 98% + staurated

Question 11

describe the pO2 in respiring tissues

Answer 11

• pO2 in the tissue capillaries is LOWER ( only 5.0 kPa)
• Hb now has a lower affinity to O2 at a lower pO2
• so oxyhaemoglobin starts to breakdown and unloads oxygen
• to be used for aerobic respiration

Question 12

explain the effect of increased respiration rate on the oxygen dissociation

Answer 12

1- tissue cells respire aerobically quickly reducing the dissolved O2
2- this reduces the pO2 to a LOWER level
3- the oxygenated blood arriving with fully saturated Hb begins to unload more oxygen and becomes less saturated
4- so more oxygen will be released from the haemoglobin to the tissue cells
5- because the surrounding pO2 is lower and so haemoglobin will have an even lower affinity to oxygen

Question 13

if a question asks what happens to % saturation at either low or high p02 , what would u do?

Answer 13

• draw a line from either high or low pO2
  upto the sigmoid curve and across to the Y axis to see the effect on Hb% saturation
  % of oxygen unloaded = lungs(high) - tissues(low)

Question 14

describe the effect of CO2 concentration on the affinity of oxygen- bohR Shift

Answer 14

-if pCO2 increases the saturation of haemoglobin decreases
- this causes the haemoglobin-oxygen dissociation curve to the RIGHT

Question 15

what happens when the haemoglobin-oxygen dissociation curve shifts to the right?

Answer 15

• Hb will have low affinity to oxygen at the respiring cells
• so more O2 is unloaded, at the SAME pO2
  -more oxygen is available to meet the oxygen demands

Question 16

Heat from respiration helps mammals to maintain a constant body temperature.

use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobin -5

Answer 16

• smaller mammal has greater SA : VR
• so there is more heat lost
• and so has a greater rate of respiration / metabolism
  -oxygen is required for aerobic respiration
• haemoglobin releases more oxygen

Question 17

where are the three basic types of haemoglobin found?

Answer 17

1- in adult humans and other species that live on land at sea level
2- in species that live in environments where the environmental pO2 is lower ( high altitude, bottom of lakes )
3- right shifted curve of species that have a Higher metabolic rate (cheetah , small mice)

Question 18

describe the properties of haemoglobin in species that live in environments where the environmental pO2 is lower ( high altitude, bottom of lakes ).

Answer 18

• the dissociation curve is shifted to the left
• hb has higher affinity for O2
• becomes fully saturated at a lower pO2 and rapidly unloads oxygen
• has a similar curve to human foetal haemoglobin

Question 19

describe the properties of haemoglobin in species that have right shifted curve and have a Higher metabolic rate (cheetah , small mice)

Answer 19

• hb has a lower affinity for O2
• so dissociates from the haemoglobin more readily
• O2 is more readily available to respiring cells

Question 20

the oxygen dissociation curve of the foetus is to the left of that for its mother.

Explain the advantage of this for the foetus

Answer 20

1- higher affinity to O2
2- at low/same/high partial pressure
3- oxygen moves from mother to foetus

Question 21

why would the lugworm require haemoglobin more like the curve towards the left ?

Answer 21

• Hb has high affinity for oxygen which enables the lugworm to saturate haemoglobin at low pO2 as between tides the O2 concentration in the burrow will be very low
  -tissues will have a slightly lower pO2 and steep curve means oxygen will still unload at the tissue when required.

Question 22

Explain how oxygen is loaded, transported and unloaded in the blood (6)

Answer 22

1- haemoglobin carries oxygen ( has a high affinity)
2- in red blood cells
3- loading/association in lungs
4- at high pO2
5- unloading/dissociation to tissues
6- at low pO2
7- unloading linked to higher carbon dioxide concentration