Mass transport systems and haemoglobin

Question 1

What is mass transport and what is it good for

Answer 1

Mass transport - Bulk movement of gases or liquids in one direction, usually via a system of vessels and tubes
- Helps to bring substances from one exchange site to another
- Helps to maintain the diffusion gradient
- Ensures effective cell activity

Question 2

What is haemoglobin

what are some qualities of where its found

Answer 2

Haemoglobin is a globular protein which is an oxygen carrying pigment (haem) found in vast quantities in the red blood cells

Red blood cells
- Biconcave discs
- Have a high surface area : Volume ratio due to biconcave discs
- Red blood cells do not contain an nucleus maximising space for oxygen

Question 3

What is the structure of haemogloblin

Answer 3

• Quaternary structure: 4 polypeptide chains (2 a-globin and 2 b-globin)
• Subunits: Each has as a prosthetic haem group
• Bonding: Subunits are held by disulphide bonds
• Haem groups: Contains fe2+, binds reversibly with oxygen to form oxyhaemoglobin

Question 4

What is the function of haemoglobin

and why is it efficent and how do substances bind?

Answer 4

• Binds to oxygen in the lungs and transports the oxygen to the tissues to be used in aerobic metabolic pathways
• As oxygen is not very soluble in water on haemoglobin it can be more efficiently carried around the body
• Existence of the iron II ion (fe2+) allows the reversible binding of oxygen

Question 5

What is the formula for oxyhaemoglobin

and symbol equation

Answer 5

oxygen + haemoglobin = oxyhaemoglobin

4O^2 + HB = Hb4O^2
(= means a reversible reaction)

Question 6

What happens when one molecule of oxygen binds to a haemoglobin molecule?

Answer 6

Results in a conformal change to the structure of haemoglobin (changes the tertiary structure) this creates another binding site making it easier for each successive oxygen molecule to bind

This can be seen on an oxygen dissociation curve

Question 7

What is the Oxygen dissociation curve

Answer 7

The curve shows rate of oxygen association and dissociation with haemoglobin at different partial pressure of oxygen
(po^2 ) - partial pressures of Oxygen

look up picture

Question 8

What is the
- Partial pressure of oxygen
- Saturation
- Affinity

Answer 8

• Partial pressure of oxygen - The measure of oxygen concentration in a mixture of gases
• Saturation - Haemoglobin is saturated when all binding sites are occupied by oxygen (4 molecules)
• Affinity - High affinity means oxygen can bind easily and dissociates slowly
  Low affinity means oxygen binds slowly and dissociates quickly

Question 9

What happens when a haemoglobin molecule is approaching saturation

Answer 9

The 4th oxygen molecule cannot bind as easily due to fewer available binding sites

This can be seen on an oxygen association curve

Question 10

What are the adaptations of foetal haemoglobin

Answer 10

• Higher affinity for oxygen = Foetal haemoglobin has a higher affinity for oxygen compared to adult haemoglobin allowing it to effectively extract oxygen from the mothers blood
• Oxygen binding = Foetal haemoglobin can bind to oxygen even at lower partial pressures
• Oxygen transfer = Differences in oxygen facilitates transfer of oxygen across placenta of mother to foetus
• Survival advantages = Adaptations are essential for foetus to receive adequate oxygen