Haemoglobin

Question 1

What is the main problem that larger organisms face regarding oxygen transport?

Answer 1

Smaller surface area to volume ratios make simple diffusion insufficient

Larger organisms require alternative methods, such as blood circulation, to transport oxygen efficiently.

Question 2

What is the role of haemoglobin in oxygen transport?

Answer 2

Haemoglobin is a complex protein that carries oxygen in the blood

It has a quaternary structure composed of four polypeptide subunits, each containing a haem group.

Question 3

How many oxygen molecules can one haemoglobin molecule carry?

Answer 3

Four oxygen molecules (O2)

Each haem group within haemoglobin can bind to one molecule of oxygen.

Question 4

What is the term used to describe oxygen combined with haemoglobin?

Answer 4

Oxyhaemoglobin

This occurs when oxygen binds to haemoglobin.

Question 5

What does the percentage saturation of haemoglobin indicate?

Answer 5

The amount of oxygen combined with haemoglobin

It is expressed as a percentage of the maximum capacity.

Question 6

What does a higher partial pressure of oxygen (pO2) result in regarding haemoglobin?

Answer 6

Increased loading of oxygen onto haemoglobin

Higher pO2 means more haemoglobin saturation.

Question 7

What is the effect of low pO2 on haemoglobin saturation?

Answer 7

Lower saturation of haemoglobin

Less oxygen is loaded onto haemoglobin at lower pO2 levels.

Question 8

What happens to oxyhaemoglobin in areas of low oxygen concentration?

Answer 8

Oxyhaemoglobin unloads oxygen to the surrounding tissues

This process is essential for supplying oxygen to respiring cells.

Question 9

Define loading in the context of haemoglobin.

Answer 9

The uptake of oxygen by haemoglobin

This occurs in environments with high pO2.

Question 10

Define unloading in the context of haemoglobin.

Answer 10

The release of oxygen from haemoglobin

This occurs in areas with low pO2.

Question 11

What is the ‘Bohr shift’?

Answer 11

A rightward shift in the oxygen dissociation curve due to increased pCO2

This results in lower affinity of haemoglobin for oxygen.

Question 12

How does increased carbon dioxide concentration affect oxygen unloading?

Answer 12

It increases the amount of oxygen unloaded from haemoglobin

Higher CO2 levels decrease haemoglobin’s affinity for oxygen.

Question 13

What is the significance of the sigmoid shape of the oxygen dissociation curve?

Answer 13

It reflects the cooperative nature of oxygen loading

The binding of the first oxygen molecule increases the likelihood of subsequent oxygen molecules binding.

Question 14

What is the effect of high altitude on haemoglobin affinity for oxygen?

Answer 14

Haemoglobin has a higher affinity for oxygen

This allows for saturation at lower pO2 levels.

Question 15

What adaptations do smaller mammals have regarding oxygen transport?

Answer 15

Higher metabolic rates and lower affinity for oxygen

This helps them unload oxygen more readily to meet respiratory demands.

Question 16

What is the role of foetal haemoglobin compared to adult haemoglobin?

Answer 16

Foetal haemoglobin has a higher affinity for oxygen
The dissociation curve is to the left

This allows it to extract oxygen from maternal blood effectively.

Question 17

What does a leftward shift in the dissociation curve indicate?

Answer 17

Higher affinity for oxygen
So more O2 loads onto Hb
So saturation of Hb with O2 increases

Seen in species adapted to low oxygen environments.

Question 18

What is the relationship between surface area to volume ratio and oxygen dissociation curves?

Answer 18

Smaller mammals lose heat more readily and have greater oxygen demands

They require haemoglobin that unloads oxygen more easily.

Question 19

What effect does temperature have on haemoglobin’s affinity for oxygen?

Answer 19

Higher temperatures decrease haemoglobin’s affinity for oxygen

This facilitates oxygen unloading during increased metabolism.

Question 20

What is the structure of Haemoglobin?

Answer 20

Globular protein with Quaternary Structure
Composed of four polypeptide chains, each containing a haem group

Question 21

When oxygen combines with haemoglobin, what is formed?

Answer 21

Oxyhaemoglobin

Question 22

What is the formula of calculating the percentage saturation of haemoglobin with oxygen?

Answer 22

(Oxygen bound to haemoglobin / Maximum Oxygen capacity of haemoglobin) x 100

Question 23

What does lower pO2 mean?

Answer 23

Less haemoglobin is saturated

Question 24

What does higher pO2 indicate?

Answer 24

More O2 is loaded onto Hb
Higher saturation of Hb ith O2

Question 25

Why does the Hb sigmoid curve have this shape?

Answer 25

PROTEINS OFTEN CHANGE SHAPE WHEN THEY BIND TO OTHER SUBSTANCES The first O2 molecule alters the tertiary structure of the Hb molecule. This exposes the 2nd and 3rd O2 BINDING sites. This makes it EASIER for 2nd & 3rd O2 molecules to bind & load. After the 3rd O2 molecule binds, it is difficult for the 4th to load because the Hb is almost full

Question 26

pO2 in lungs

Answer 26

The partial pressure of O2 (pO2) is highest Hb has a higher affinity for O2 at a high pO2. Haemoglobin becomes (almost) fully saturated

Question 27

pO2 in respiring tissues

Answer 27

The pO2 in the tissue capillaries is LOWER Haemoglobin now has a lower affinity for O2 at a lower pO2 so the oxyhaemoglobin starts to break down and unloads oxygen.

Question 28

What happens when there is higher-than-normal pCO2?

Answer 28

Haemoglobins affinity for Oxygen is even lower. If pCO2 increase the saturation of haemoglobin decreases. This causes the haemoglobin-oxygen dissociation curve to shift to the right

Question 29

What is the Bohr shift?

Answer 29

In higher-than-normal pCO2 Haemoglobins affinity for Oxygen is even lower. If pCO2 increase the saturation of haemoglobin decreases. This causes the haemoglobin-oxygen dissociation curve to shift to the right

Question 30

Why does Hb has a lower affinity to O2 at higher levels of CO2?

Answer 30

When CO2 dissolves in the blood it makes the blood more acidic, thus lowering the pH. As Hb is a protein, a change in pH slightly alters its tertiary structure.

Question 31

What happens the more that tissue cells respire?

Answer 31

The more that tissue cells respire, the more the carbon dioxide concentration will increase and cause a shift to the right in the oxyhaemoglobin dissociation curve. · Hb now has a lower affinity to oxygen at the respiring cells. · As a result, more oxygen is unloaded from the haemoglobin, at the same pO2, as it becomes less saturated. · MORE oxygen is now available to meet the oxygen demands of the respiring cells

Question 32

Why would the tissue cells respire MORE?

Answer 32

Because of exercise

Question 33

What does dissolved CO2 do?

Answer 33

Makes the blood more acidic Changes the tertiary structure of Hb

Question 34

Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins. (5)

Answer 34

Smaller mammal has a larger surface area to volume ratio; So more heat lost; Larger SA:Vol ratio animals have a greater rate of respiration; Oxygen is required for aerobic respiration; So Haemoglobin unloads more oxygen because haemoglobin has lower affinity;

Question 35

Which organisms have a form of haemoglobin where the dissociation curve is shifted to the left?

Answer 35

Species that live in places of lower pO2: High altitudes Bottom of lakes Underground Lug worms OR Human foetus

Question 36

Why does the dissociation curve shift to the left in some species?

Answer 36

Environmental pO2 is lower their Hb has a higher affinity for O2 Hb has a higher saturation at a lower pO2 So Hb rapidly unloads O2 when the Hb passes into the tissues

Question 37

Which animals have a form of haemoglobin that has a curve shifted to the right?

Answer 37

Species with a high metabolic rate. So very active animals like cheetahs or small mice because they have a larger SA:V

Question 38

Why does the dissociation curve shift to the right in some species?

Answer 38

They respire a lot more so more O2 is required so Hb has a lower affinity for O2 So O2 unloads from the Hb more readily O2 is more readily available to respiring tissues

Question 39

Explain how oxygen is loaded, transported and unloaded in the blood. (6)

Answer 39

1. Haemoglobin has a high affinity for oxygen 2. In red blood cells; 3. Loading in lungs; 4. at high p.O2; 5. Unloads to respiring tissues; 6. at low p.O2; 7. Unloading linked to higher carbon dioxide concentration;

Question 40

Explain how an arteriole can reduce the blood flow into capillaries

Answer 40

Muscle contracts Which narrows the lumen