Haemoglobin

Question 1

What is haemoglobin?

Answer 1

a large protein with a quaternary structure = it carries oxygen around the body

Question 2

Describe the structure of haemoglobin

Answer 2

primary structure = amino acid sequence of the four polypeptide chains

secondary structure = polypeptide chains folded into an alpha helix

tertiary structure = each polypeptide chain is folded in a precise shape

quaternary structure = all four polypeptides are linked to form an almost spherical form. Each polypeptide is associated with a haem group, which contains Fe 2+ ion. Fe2+ can bind to oxygen. Therefore haemoglobin can bind to four o2 moles

Question 3

What is the function of haemoglobin?

Answer 3

load oxygen in the lungs and deliver it to the respiring tissues

Question 4

What does affinity mean?

Answer 4

the level of attraction haemoglobin has to oxygen
(high affinity = strong attraction, low affinity = weak attraction)

-

Question 5

What does loading/associating and unloading/disassociating mean?

Answer 5

loading/associating = when haemoglobin binds with oxygen

unloading/disassociating= when haemoglobin release its oxygen

Question 6

Role of haemoglobin in oxygen transport?

Answer 6

haemoglobin has High Affinity in the lungs– due to high partial pressure of oxygen and low partial pressure of carbon dioxide,

so haemoglobin associates oxygen in the lungs and becomes saturated (full)

the haemoglobin is transported in the blood in the red blood cell

at the respiring tissues, haemoglobin has Low Affinity

– due to low partial pressure of oxygen and high partial pressure of carbon dioxide,

so oxygen is dissociated and haemoglobin becomes unsaturated

Question 7

Why are there different haemoglobins which have different affinities?

Answer 7

change in the environment (e.g. ph or temperature) causes haemoglobin to change its tertiary structure and therefore affects the way it functions

different shape of the molecule due to a slightly different sequence in amino acid (primary structure) = different tertiary structure = different oxygen-binding properties

Question 8

How do you know haemoglobin is a protein with a quaternary structure?

Answer 8

4 oxygen is able to binds to it (each polypeptide chain has a haem group which can bind to one o2 molecule)

Question 9

Draw the oxygen dissociation curve for adult human haemoglobin

Answer 9

Question 10

Explain the shape for the oxygen dissociation curve

Answer 10

low pressure -beginning of curve: the shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits because they are closely united, therefore low oxygen concentration means little oxygen binds to haemoglobin

higher oxygen partial pressure - Middle of the curve (when the gradient of the curve steepens): first oxygen molecule changes the Quaternary structure of the haemoglobin molecule = changes shape = easier or the other subunits to bind to an oxygen molecule **(positive cooperativity)**

End of the curve: longer for the oxygen molecule to bind to due to it being more difficult to find a binding site

Question 11

What does it mean when the oxygen dissociation curve is more the left and when it is more the right?

Answer 11

left = greater affinity of haemoglobin for oxygen

right = lower affinity of haemoglobin for oxygen (unloads really easily)

Question 12

What is the Bohr effect?

Answer 12

the greater the CO2 concentration, the more readily the haemoglobin releases its oxygen (as it has a lower affinity in the presence of CO2)

Question 13

How does co2 concentration affect haemoglobin?

(mention pH)

Answer 13

low co2 concentration = haemoglobin changes shape into one of high affinity, so is able to load oxygen more readily, due to pH being slightly high

high co2 concentration = pH is lower as CO2 is acidic = lower affinity so oxygen disassociates more readily for the same partial pressure of oxygen, unloads more oxygen and has reduced saturation

Question 14

Why does haemoglobin in the lungs have a higher affinity than haemoglobin in the respiring tissue?

Answer 14

Because in the lungs there is a low co2 concentration (due to the CO2 diffusing across the exchange surface and being excreted) and a high oxygen concentration

In respiring tissue, the co2 concentration is high (as the products of respiration is CO2 +water + energy) and the concentration of oxygen is low due to oxygen being used in respiration. This makes the affinity of haemoglobin in respiring tissue low

Question 15

Why is low-affinity haemoglobin good for respiring tissues?

Answer 15

this means more readily oxygen is unloaded so more oxygen is available for respiriation

Question 16

Benefit of fetal haemoglobin having high affinity? (based on exam question)

Answer 16

fetal haemoglobin’s ODC will be to the left, it has high affinity

the oxygen will dissociate from the mother’s haemoglobin and associate with the fetal haemoglobin at the low partial pressures of oxygen in the placenta (due to the fetal one having a higher affinity),

so the haemoglobin associates more readily, it has enough oxygen for its needs.

Even at low partial pressures of oxygen, it can reach 100% saturation

Question 17

Why do adults not keep with fetal haemoglobin?

Answer 17

the high affinity will mean less oxygen will be unloaded at the respiring tissues

Question 18

What is the affinity for small organisms like?

Answer 18

have a large surface area to volume ratio, lose a lot of heat, needs to respire to generate heat, therefore has a low affinity, so unloads enough oxygen for the cells demand of more respiration

Question 19

What does a closed, double circulatory system mean?

Answer 19

blood is confined to vessels and passes twice through the heart for each complete circuit of the body

Question 20

What would happen if the body had a single circulatory system?

Answer 20

When the blood is passed through the lungs, the blood pressure is reduced. This means that the blood will always be at low pressure when it’s passing around the body, which would make circulation slow, which will not accommodate mammals’ high rate of metabolism

Question 21

Draw the plan of the mammalian circulatory system

Answer 21

Question 22

What does blood transport?

Answer 22

respiratory gases, products of digestion, metabolic wates and hormones

Question 23

Label the heart

Answer 23