Haemoglobin

Question 1

In an oxygen dissociation curve, what does it mean of the graph shifts right?

Answer 1

haemoglobin has a lower affinity to oxygen

oxygen is released more readily at a lower partial pressure of oxygen

Question 2

In an oxygen dissociation curve, what does it mean of the graph shifts left?

Answer 2

haemoglobin has a higher affinity to oxygen

oxygen joins more easily at the partial pressure of oxygen.

Question 3

what shape is the oxygen dissociation curve?

Answer 3

sigmoid (S-shaped)

Question 4

what is the equation for oxyhaemoglobin?

Answer 4

Hb+4O2-> Hb4O2 or HbO8

Question 5

what does 100% saturation mean?

Answer 5

Every haemoglobin molecule is carrying 4 oxygen molecules (4O2)

Question 6

what does 0% saturation mean?

Answer 6

No haemoglobin molecule is carrying oxygen.

Question 7

what happens to the affinity of haemoglobin at a low partial pressure of Oxygen?

Answer 7

Haemoglobin has a low affinity for oxygen so haemoglobin dissociates with oxygen.

Question 8

what happens to the affinity of haemoglobin at a high partial pressure of Oxygen?

Answer 8

Haemoglobin has a high affinity for oxygen so haemoglobin combines with oxygen.

Question 9

Explain the oxygen dissociation curve

Answer 9

Because there is more Oxygen, haemoglobin is more likely to form oxyhaemoglobin.
Slowly first because it is difficult for the first O2 molecules to join. Then it increases more quickly because as the first O2 joins, the Hbs shape alters slightly making it easier for others to join. Then as it becomes more saturated it gets harder for O2 to join again.

Question 10

How many haem groups are in a red blood cell?

Answer 10

4 (each one can combine with one O2 molecule)

Question 11

what are haem groups made of?

Answer 11

Fe2+ ions

Question 12

Describe the oxygen dissociation curve

Answer 12

As partial pressure of oxygen increases so does the %saturation of haemoglobin with oxygen.
Slowly up to [insert value], then more quickly up to [insert value], before slowing down again from [insert value].

Question 13

What % of CO2 dissolves into the blood plasma?

Answer 13

5%

Question 14

what % of CO2 is transported as carbaminohaemoglobin?

Answer 14

10%

Question 15

What is carbaminohaemoglobin?

Answer 15

When CO2 attaches to the protein part of the haemoglobin (not haem group like O2)

Question 16

what % of CO2 is transported as hydrogen carbonate ions?

Answer 16

85%

Question 17

How are Hydrogen carbonate ions formed?

9 steps

Answer 17

• Respiring cells release carbon dioxide
• Diffuses into plasma
• Diffuses into erythrocytes
• CO2 and water react to form Carbonic acid (H2CO3)
• This is catalysed by carbonic anhydrase
• Hydrogen ions dissociate
• Hydrogen carbonate ions form (can leave the RBCs
• If they leave chloride ions enter (replace charge)
• This is called the chloride shift

Question 18

Why don’t H+ ions make the RBC acidic?

7 steps

Answer 18

• There is oxyhaemoglobin in erythrocytes
• Hb acts as a buffer (controls pH)
• Hydrogen ions compete with Oxygen
• Oxygen dissociates to allow H+ ions to bind
• Haemoglobinic acid forms
• Oxygen diffuses into blood plasma
• Oxygen diffuses into respiring tissue

Question 19

What is the Bohr effect?

Answer 19

As CO2 increases the graph shifts right.

Question 20

explain the Bohr effect

Answer 20

The graphs shifts right as CO2 increases because as CO2 increases so does the number of H+ ions formed so Hb has a lower affinity to oxygen at the same partial pressure of oxygen.
Oxygen dissociates more easily.
Hb acts as a buffer so releases O2 to pick up H+ ions.

Carbaminohaemoglobin also lowers the affinity to O2.