transport in animals part 2

Question 1

describe the role oxygen plays in haemoglobin

Answer 1

• Oxygen is transported via haemoglobin
• Each molecule of haemoglobin contains a haem group with Fe2+, there are 4 haem groups.
• The iron ion is the one that attracts the oxygen and holds the molecule
• Each haem group has an high affinity for oxygen, and as there are 4 haem group each one can hold one oxygen so one molecule of haemoglobin can carry 4 oxygen

Question 2

explain dissociation

Answer 2

• In the alveoli there is a high partial pressure of oxygen so oxygen is loaded with the haemoglobin becoming oxy-haemglobin – its associates with the haemoglobin
• The blood then goes to respiring tissue where there is a low partial pressure of oxygen as the oxygen has been used up, the oxygen is therefore unloaded from the haemoglobin. This is called dissociation

Question 3

explain the graph shape

Answer 3

• When haemoglobin assciates with oxygen an s-shaped graph is formed this is called the haemoglobin dissociation graph
  1. At low oxygen tension the haemoglobin does not associate with the oxygen molecules as the haem groups and iron that attract the oxygen are in the centre of the hb molecule therefore it is difficult for the oxygen to reach the heam group and bind with it
  2. As oxygen tension rise the diffusion gradient of oxygen into haemoglobin increases and eventually one oxygen asscoiates this causes the shape of the haemoglobin molecule to change – confornamtional change – allowing more oxygen to associate easily therefore the steepness of the graph increases
  3. As it approaches 100% saturation the graph levels off

Question 4

why does fetal haemoglobin have a higher affinity for oxygen

Answer 4

• Has a higher affinity for oxygen
• The dissociation curve it too the left of the adult one
• This is because fetal haemoglobin must be able to assicate in an environment which the oxygen tension is low enough to make adult haemoglobin dissociate
• The fetal haemoglobin absorbs oxygen from the fluid around the placenta reducing the oxygen tension even further as a result more oxygen dissuades blood fluid into the placenta reducing the oxygen tension within the mothers blood this makes the maternal haemoglobin release more oxygen – dissociation

Question 5

how is carbon dioxide gotten rid off

Answer 5

• 5% dissolved directly into the blood plasma
• 10% joins with haemoglobin to from carbaminohaemglobin
• 85% transported in the form of hydrogen carbonate ions

Question 6

how are hydrogen carbonate ions formed

Answer 6

1. Co2 is released by respiring cells
2. Co2 combines with the water in the red blood cell
3. Forms carbonic acid by using the enzyme carbonic anhydrase
4. Carbon acid dissociates to from H+ (proton) and HCO3-
5. The HCO3- leaves the cell by diffusion and chlorine ions with a 1- charge diffuse into the cell to make sure the charge on the cell does not change this is called the chloride shift
6. The H+ ions bind with the haemoglobin to form haemogloboinc acid (this is a buffer solution resisting change to PH therefore maintains the Ph)
7. Then the oxyhaemoglobin releases 4 oxygen cells which will be respiring

Question 7

describe the bohr effect

Answer 7

1. Carbon dioxide will dissociate to form a proton and a hydrogencarbonate
2. The proton will combine with the haemoglobin as HB has a higher affinity for hydrogen than for oxygen so the H+ (proton) displaces the oxygen
3. Oxygen is more readily unloaded therefore there is a need for a higher partial pressure of oxygen to allow it to be taken on
4. When there is a high partial pressure of carbon dioxide there are more H+ ions produces therefore more H+ ions been taken by the HB so more oxygen is released