1.2.2 - Transport in Animals (Carriage of O2 and CO2) Part 11 & 12

Question 1

Respiring tissues releases CO₂ into the blood via diffusion.

5% dissolves into the _____.

10% binds with ________ to make ________.

85% reacts with_______ in red blood cells to make ______ ______.

Answer 1

5% dissolves in the plasma.

10% binds with haemoglobin to make HHb-CO_2.

85% reacts with water in the red blood cells to make carbonic acid.

Question 1

What is the Bohr effect?

Answer 1

• The Bohr effect - refers to a change in the shape of the oxyhaemoglobin curve whe carbon dioxide is present.
• Carbon dioxide causes for the oxygen to be released more readily due to the increase in H⁺ ions. The more carbon dioxide present, the more oxygen will be released.

Question 2

Explain why fetal haemoglobin must have a higher affinity for oxygen than adult haemoglobin.

Answer 2

• Fetal haemoglobin have a higher affinity because they need to be able to take up oxygen from an environment that makes adult haemoglobin release oxygen.
• This reduces the oxygen tension within the fluid of the mother’s blood, making the maternal haemoglobin release more oxygen.

Question 3

What is the chloride shift and why is it vital?

Answer 3

Chloride shift - When the hydrogen carbonate ions (HCO₃⁺) diffuse out, the chloride ions (Cl^-) diffuse in.

This is vital because it maintains the charge of the blood cell.

Question 5

How many oxygen molecules can haemoglobin hold up to?

Answer 5

Haemoglobin can carry up to 4 oxygen molecules.

Question 6

Describe and explain the shape of the adult oxyhaemoglobin dissociation curve.

Answer 6

• The curve is in the shape of an S.
• This is because an low oxygen tension, haemoglobin does not readily take up oxygen. The haem groups are in the centre of the haemoglobin molecule, making it difficult to associate with, hence the low saturationwith oxygen.
• As oxygen tension rises, so does the diffusion gradient. Eventually one molecule diffuses in and associates with a haem group. This changes the shape of the haemoglobin (conformational change), allowing more oxygen to diffuse in, hence the steepness of the curve.
• It is difficult for the fourth oxygen molecule to diffuse in so the curve levels off as saturation approaches 100%.

Question 7

What is the name of the enzyme that combines CO₂ and H₂O in the red blood cell?

Answer 7

Carbonic anhydrase.

Question 8

What is the role of the H⁺ ions in the red blood cell?

Answer 8

The H⁺ ions disrupts the Hb.O₂ molecule (oxyhaemoglobin), causing the O₂ gas to release into the blood plasma.

Question 9

Haemoglobin is a complex protein with _____ subunits. Each subunit consists of a _______ (protein) chain and a _____ (non-protein) group. The haem group is said to have an ______ (attraction) for oxygen.

Answer 9

Haemoglobin is a complex protein with four subunits. Each subunit consists of a polypeptide (protein) chain and a haem (non-protein) group. The haem group is said to have an affinity (attraction) for oxygen.

Question 10

Carbonic acid is a weak acid. What does it easily dissociate into?

Answer 10

• H⁺ ions
• HCO₃^- ions.