S10) Protein Function — Oxygen Transport Flashcards Preview

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Flashcards in S10) Protein Function — Oxygen Transport Deck (15)
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1
Q

What is haemoglobin and what does it do?

A
  • Haemoglobin is a tetrameric haem protein found in blood which carries oxygen from the respiratory organs to body tissues
  • There, it releases the oxygen to permit aerobic respiration in order provide energy for metabolism
2
Q

What is myoglobin and what does it do?

A
  • Myoglobin is a monomeric haem protein found mainly in muscle tissue where it serves as an intracellular storage site for oxygen
  • During periods of oxygen deprivation oxymyoglobin releases its bound oxygen which is then used for metabolic purposes
3
Q

Describe the binding of oxygen to haemoglobin

A
  • O2 binds to haemoglobin via the Fe atom in the haem prosthetic group
  • O2 binding to haemoglobin shows a sigmoid shaped dependence on [O2]
4
Q

Describe the binding of oxygen to myoglobin

A
  • O2 binds to myoglobin via the Fe atom in the haem prosthetic group
  • O2 binding to myoglobin shows a hyperbolic dependence on [O2]
5
Q

Describe the overall structure of haemoglobin

A
  • Composed of 4 polypeptide chains in α2β2 tetramer
  • Each chain contains an essential haem prosthetic group
6
Q

Explain how haemoglobin undergoes a structural change on oxygen binding

A
  • Deoxyhaemoglobin exists in either the low affinity T state or the high affinity R state
  • Oxygen binding promotes stabilisation of the R state
7
Q

Why is the oxygen-dissociation curve for haemoglobin sigmoidal?

A
  • Haemoglobin ‘co-operatively binds’ to oxygen
  • The binding of one oxygen molecule promotes the binding of the next
8
Q

What is the benefit of the sigmoidal binding curve of haemoglobin?

A
  • O2 can be efficiently transported from the lungs to the tissues
  • Haemoglobin is more sensitive to small differences in [O2]
9
Q

2,3-BPG is a molecule which regulates oxygen binding.

What is the effect of the binding of 2,3-BPG to deoxyhaemoglobin?

A
  • 1 BPG binds per haemoglobin tetramer and decreases the affinity for O2
  • [BPG] increases at high altitudes, promoting O2 release at the tissues
10
Q

Describe he regulation of oxygen binding in terms of CO2 and H+

A

Binding of H+ and CO2 lowers the affinity of haemoglobin for oxygen

11
Q

What is the benefit of the Bohr effect?

A
  • Metabolically active tissues produce large amounts of H+ and CO2
  • The Bohr effect ensures the delivery of O2 is coupled to demand
12
Q

In terms of oxygen binding, explain why is carbon monoxide poisonous?

A

Carbon monoxide (CO) is a poison because it combines with ferromyoglobin and ferrohaemoglobin to block oxygen transport

13
Q

CO binds to haemoglobin 250x more readily than O2.

Illustrate the impact of this on the oxygen binding curve of haemoglobin

A
14
Q

HbF is the major haemoglobin in foetal blood.

Why is it important?

A

Higher binding affinity of HbF for O2 than HbA allows transfer of O2 to foetal blood supply from the mother

15
Q

Identify 2 properties of red blood cells with the HbS protein as seen in sickle cell anaemia

A
  • More prone to lyse (anaemia)
  • More rigid (black microvasculature)