Role of Haemoglobin (Hb)

Question 1

What is the main role of haemoglobin?

Answer 1

Carries oxygen and carbon dioxide around the body

Question 2

What type of molecule is haemoglobin?

Answer 2

A protein

Question 3

What does each molecule of haemoglobin contain?

Answer 3

4 haem groups, each able to bond with one molecule of oxygen

Question 4

What does this contents in haemoglobin therefore mean?

Answer 4

That each molecule of haemoglobin can carry four oxygen molecules or eight oxygen atoms

Question 5

What is formed when haemoglobin is saturated with oxygen?

(O2 binds to Hb)

Answer 5

Oxyhaemoglobin

Question 6

What is the equation for this formation?

Answer 6

Oxygen + Haemoglobin ⇌ Oxyhaemoglobin

Question 7

What does the binding of the first O2 molecule result in?

Answer 7

A conformational change in structure of haemoglobin molecule

Question 8

What does this conformational change mean?

Answer 8

It makes it easier for each successive oxygen molecule to bind (cooperative binding)

Question 9

When does the reverse of this happen?

Answer 9

When oxygen dissociates in tissues

Question 10

What are the 3 factors which determine the affinity of haemoglobin for oxygen?

Answer 10

-pO2
-pCO2
-Type of Hb (fetal or adult)

Question 11

What does ‘p’ stand for in pO2 and pCO2?

Answer 11

Partial Pressure

Question 12

What happens as pO2 increases?

Answer 12

Haemoglobin’s affinity for O2 increases.

Question 13

What does affinity mean?

Answer 13

the strength by which two (or more) molecules interact or bind.

Question 14

What does it mean if the affinity has a low value?

Answer 14

The smaller its value, the greater the affinity between two molecules and vice-versa

Question 15

Why is the dissociation curve s-shaped? Start at top and go to bottom

Answer 15

-At top, it’s hard for 4th O2 to bind to as Hb becomes saturated with O2 so it’s shape changes making it difficult for other O2’s to bind
-In middle, easier for 2nd and 3rd O2’s to bind as when 1st O2 binds, it causes Hb’s shape to change making it easier for other O2’s to bind
-At bottom, it’s hard for 1st O2 to bind

Question 16

What type of saturation is at the bottom of the dissociation curve?

Answer 16

Low as haemoglobin isn’t carrying much O2
-few haem groups bound to O2

Question 17

What type of saturation is at the middle of the dissociation curve?

Answer 17

Medium as it’s easier for O2 to be picked up
-more haem groups to bound to O2

Question 18

What type of saturation is at the top of the dissociation curve?

Answer 18

High as all of haemoglobin as all haem groups are bound

Question 19

What happens are pCO2 increases?

Answer 19

Haemoglobin’s affinity for O2 decreases causing haemoglobin to unload its O2(right where it’s needed) creating the Bohr effect

Question 20

What is the Bohr effect?

Answer 20

Where haemoglobin dissociation curve moves to right as haemoglobin gives up its O2 more readily when pCO2 is high

Question 21

Why is the Bohr effect important in the body?

Answer 21

-In active tissues with high partial pressure of CO2, haemoglobin gives up oxygen more readily
-In lungs where the proportion of CO2 in air is relatively low, oxygen binds to haemoglobin molecules easily

Question 22

What is the pO2 and pCO2 like in lungs?

Answer 22

pO2 is high and pCO2 is low

Question 23

What is the pO2 and pCO2 like in respiring tissues?

Answer 23

pO2 is low and pCO2 is high

Question 24

Bohr Effect is result of increased acidity due to dissolved CO2. What 2 things do hydrogen ions do?

Answer 24

-Lower pH
-Reduce affinity of Hb for O2

Question 25

How is CO2 transported?

Answer 25

Is carried from tissues 3 ways

Question 26

What are the 3 ways in which CO2 is transported?

Answer 26

-In solution in blood plasma
-In combination with haemoglobin
-As hydrogen carbonate ions in blood plasma

Question 27

How much of CO2 is transported in solution in blood plasma?

Answer 27

5%

Question 28

How much of CO2 is transported in combination with haemoglobin?

Answer 28

10%

Question 29

How much of CO2 is transported as hydrogen carbonate ions in blood plasma?

Answer 29

Most-80%

Question 30

How is CO2 transported in combination with Hb?

Answer 30

-Amino Acid group on Hb and CO2 in plasma enters into cell and adds to AA group
-This forms carbaminohaemoglobin

Question 31

How is CO2 transported as hydrogen carbonate ions in blood plasma?

Answer 31

It’s converted into hydrogen carbonate ions (HCO3-) in the cytoplasm of red blood cells

Question 32

How is Haemoglobinic Acid formed?

Answer 32

Hydrogen ions produced from dissociation of Carbaminohaemoglobin and hydrogen carbonate ions bind to Hb

Question 33

What does this formation of Haemoglobinic Acid cause?

Answer 33

Causes Hb to release its oxygen

Question 34

In what forms does haemoglobin exist in?

Answer 34

Adult and Foetal

Question 35

What other form of haemoglobin is there which is less common?

Answer 35

Myoglobin which is found in muscles of vertebrates

Question 36

What is the role of Myoglobin?

Answer 36

Concerned with storage rather than transport of oxygen
-is like a last resort

Question 37

Why is foetal and adult haemoglobin different?

Answer 37

If mother and foetus had the same Hb, there would be no reason for oxygen to pass from one to another (starvation of oxygen would occur)

Question 38

Where are foetal RBCs produced?

Answer 38

In liver

Question 39

Where does this production happen after birth?

Answer 39

In bone marrow with adult Hb

Question 40

Why does foetal Hb have a higher affinity for O2 than adult?

Answer 40

As it’s made from 2 alpha and 2 beta polypeptide chains

Question 41

What are the 2 reasons why it is important that foetal Hb has a higher affinity?

Answer 41

-pO2 at placenta is lower than at lungs as some O2 is used up en-route by mothers body
-we need foetal Hb to load O2 while mother Hb unloads O2

Question 42

What happens to the dissociation for foetal Hb?

Answer 42

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