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Molecules, Genes and Disease > MGD 9.1 Haemoglobin and Myoglobin > Flashcards

MGD 9.1 Haemoglobin and Myoglobin Flashcards

Haemoglobin and Myoglobin (56 cards)

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1
Q

What is the function of haemoglobin and myoglobin?

A

They bind and transport molecular oxygen

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2
Q

Why are oxygen carriers essential? (2)

A
  1. Oxygen is non-polar, so it’s poorly soluble in water 2. Poorly diffusible = in a large multicellular organism oxygen will not reach the target tissues by diffusion alone
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3
Q

Where is myoglobin found?

A

In muscle tissue

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4
Q

Where is haemoglobin found?

A

In the blood, in red blood cells

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5
Q

What is the function of haemoglobin?

A

It’s responsible for the transport of oxygen throughout the body - Responds to oxygen availability

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6
Q

How does haemoglobin function? (3)

A
  1. binds to oxygen in the lungs 2. permits transfer of oxygen from haemoglobin in the blood to cells and tissues 3. permits transfer of oxygen from haemoglobin in the blood to muscle myoglobin
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7
Q

What is the function of myoglobin? (2)

A
  1. It stores and facilitates diffusion of oxygen in the muscle 2. Has a high affinity for oxygen 3. Responds to muscle’s oxygen needs
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8
Q

What are the normal values of pO2 in mixed alveolar gas and pCO2 in mixed alveolar air? (2)

A
  1. PO2 in mixed alveolar gas= 100mmHg= 13KPa 2. PCO2 in mixed alveolar air= 40mm/Hg= 5.3KPa
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9
Q

What are the normal values of pO2 and pCO2 in venous blood? (2)

A
  1. PO2 in venous blood= 40 mmHg= 5.3KPa 2. PCO2 in venous blood=45 mmHg= 6kPa
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10
Q

What are the normal values of pO2 and pCO2 in venous blood? (2)

A
  1. PO2 in arterial blood = 75-100mmHg = 11-13 KPa 2. PCO2 in Arterial blood= 35-45 mmHg= 4-6KPa
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11
Q

What are the normal values of pO2 and pCO2 in venous blood? (2)

A
  1. PO2 in peripheral tissues = 40 mmHg = 5.3 KPa 2. PCO2 in peripheral tissues = 45-50mmHg = 6-6.5KPa
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12
Q

What facilitates haemoglobin and carbon dioxide transport?

A

Also the process is facilitated by red cell carbonic anhydrase

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13
Q

What is the Haldane effect?

A

Haemoglobin gives up CO2 when pO2 rises (lungs) and binds CO2 when pO2 falls (tissues)

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14
Q

What does haem consist of?

A

• Haem consists of a porphyrin ring and an Fe atom bound to 4 N atoms of the ring

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15
Q

How does Fe2+ bind to oxygen?

A

• Fe2+ can make bonds to oxygen on either side of the plane (though only one at a time)

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16
Q

How does oxygen bind to the haem group in haemoglobin and myoglobin?

A

• 1 molecule of O2 binds to the haem group in myoglobin and haemoglobin

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17
Q

How is Fe bound in haemoglobin and myoglobin?

A

• Fe atom is bound to the protein via a histidine residue (proximal histidine) on the other side of the ring

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18
Q

What are the features of myoglobin structure? (4)

A

1 • 153aa, compact, tightly folded 2 • 75%-helical (8 helices) 3 • His 93 in the 8th -helix is covalently linked to Fe 4 • Haem is linked into the Fe helix by the proximal and distal histidine

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19
Q

What is the simple hyperbolic binding curve?

A

•Oxygen binding to myoglobin shows a hyperbolic dependence on oxygen concentration

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20
Q

What is the shape of the oxygen dissociation curves for haemoglobin?

A

haemoglobin is sigmoidal

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21
Q

What are the features of haemoglobin structure? (FIRST 3)

A

1 • alpha 2 beta 2, tetramer (adult haemoglobin) 2 • 4 polypeptide chains: 2 alpha chains (141 aa), 2 beta chains (146 aa) 3 • Each chain contains a haem prosthetic group that binds one O2

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22
Q

What are the features of haemoglobin structure? (LAST 1)

A

4 • Conformation of each polypeptide chain is very similar to that of myoglobin, similar amino acids

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23
Q

What does X ray crystallography of haemoglobin show?

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A

X ray crystallography shows deoxyhaemoglobin can exist in low affinity T state or high affinity R state

24
Q

What does oxygen binding promote?

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A

Oxygen binding promotes stabilisation of the R state and a 15% rotation in the molecule that enhances binding of oxygen

25
Why is the oxygen binding curve for haemoglobin sigmoidal?
Cooperative binding of oxygen
26
Why is the oxygen binding curve for haemoglobin sigmoidal? (3)
1 • binding affinity for oxygen increases as more oxygen molecules bind to Hb subunits 2 • binding of 1st O2 molecule to 1 subunit is hard– low affinity 3 • binding of last O2 molecule to 4th subunit is very easyhigh affinity
27
Co-operative binding: the oxygen binding curve for haemoglobin is sigmoidal (3)
1. Deoxyhaemoglobin has a low affinity for O2. 2. Successive O2 binding incrementally increases the affinity for the other sites. 3. The steepest part of the curve coincides with a pO2 common to tissues.
28
What is the importance of the sigmoidal binding curve of haemoglobin? (2)
1. The binding of one oxygen molecule promotes the binding of subsequent molecules 2. The sigmoidal binding curve of haemoglobin means that O2 can be efficiently carried from the lungs to the tissues.
29
What is haemoglobin a mix of?
Hb is a mix of low and high affinity states resulting in a physiologically functional intermediate state
30
What is haemoglobin more sensitive to?
More sensitive to small difference in O2 concentrations
31
What is the pO2 in the mixed venous blood in the lungs?
• In the lungs the mixed venous blood in the distributaries of the pulmonary arteries have a pO2 at 40 mmHg (5.3 KPa) and saturation of ~75%.
32
What is the pO2 of the air in the alveoli?
• The pO2 of the air in the alveoli is 100mmHg (13KPa). There is a gradient.
33
Association and dissociation of oxygen (2)
1 • Cooperative nature of O2 binding to Hb means single unoccupied heme groups have high affinity for O2. 2 • Allows the capture of maximal O2 as it diffuses across the blood-gas interface
34
Where is the oxygen dissociation curve for haemoglobin the steepest?
1. At oxygen concentrations that occur in the tissues 2. This permits oxygen delivery to respond to small changes in pO2
35
When does the oxygen dissociation curve for haemoglobin plateau?
approx. 60 mm Hg (8KPa)
36
What does the oxygen dissociation curve of haemoglobin explain?
explains Hb’s ability to bind oxygen in the lung and release it to the tissues
37
What is the transfer of oxygen facilitated by?
• Transfer facilitated by steepness of the pressure gradient between blood and mitochondria where it is used for oxidative phosphorylation
38
What is the Bohr effect?
• H+ and CO2 both bind to haemoglobin molecules • Binding of H+ and CO2 lowers the affinity of haemoglobin for O2
39
Where in the body does the Bohr effect take place?
• Metabolically active tissues produce large amounts of H+ and CO2 (HCO3-) • H+ facilitates O2 unloading by shifting the dissociation curve to the right increasing CO2 carrying capacity
40
What does the Bohr effect ensure?
• The Bohr effect ensures the delivery of O2 is coupled to demand
41
What compound inside red blood cells regulates oxygen binding?
2-3 diphosphoglycerate decreases haemoglobin’s oxygen affinity
42
What stimulates 2-3 diphosphoglycerate?
•Chronic hypoxemia caused by pathological lung conditions or high altitude stimulates 2-3 DPG (2 3BPG) • intermediate from glycolysis
43
How does chronic hypoxemia stimulate 2-3 diphosphoglycerate?
•Shifts the haemoglobin oxygen curve to the right. •increasing tissue accessibility to oxygen
44
Where can 2,3-Bisphosphoglycerate (BPG) be found?
Present in red blood cells at ~5 mM
45
How many 2,3-Bisphosphoglycerate (BPG) compounds are in haemoglobin?
1 BPG binds per haemoglobin tetramer and decreases the affinity for O2
46
When does 2,3-Bisphosphoglycerate (BPG) concentration increase?
• BPG concentration increases at high altitudes, promoting O2 release at the tissues. • Sickle Cell Anaemia
47
Why is carbon monoxide a poison?
• Carbon monoxide(CO) is a poison because it combines with ferromyoglobin and ferrohaemoglobin and blocks oxygen transport • CO binds to haemoglobin 250x more readily than O2
48
When is carbon monoxide poisoning fatal?
• Fatal when COHb is >50%
49
What else does CO binding affect?
• CO binding also acts to increase the affinity for oxygen for unaffected subunits • Oxygen is therefore not delivered to the tissues
50
What can lead to high levels of carbon monoxide in homes?
• Faulty boilers
51
What are the features of carbon monoxide?
• Colourless • Odourless • Tasteless
52
What are the 2 types of CO poisoning?
• Acute poisoning • Chronic poisoning
53
What are the common symptoms of carbon monoxide poisoning? (6)
1. Headache, dizziness and fatigue 2. Blurry or double vision 3. Shortness of breath 4. Confusion 5. Chest pain 6. Nausea and vomiting
54
How does CO poisoning present after death?
CO poisoning turns skin a bright cherry colour that persists after death
55
What are the different diseases that causes abnormal red blood cell morphologies? (Abnormal red blood cell morphologies are associated with various types of anaemia)
1. Sickle cell disease 2. Thalassemia 3. Megaloblastic anaemia 4. Iron deficiency 5. Hereditary spherocytosis 6. Hereditary elliptocytosis 7. Haemoglobin C disease 8. Acanthocytosis 9. DIC, TTP, Heart valve prosthesis
56
How to convert between torr, mmHg and KPa?
1 torr=1mmHg=0.133KPa

Molecules, Genes and Disease (2 decks)

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