Haemoglobin and oxygen + Cardiovascular disease

Question 1

What is haemoglobin?

Answer 1

Protein molecules with a quaternary structure

Question 2

What is a haemoglobin made up of?

Answer 2

A quaternary structure in which all 4 polypeptides are linked together to form an almost spherical molecule

Question 3

What is each polypeptide in haemoglobin associated with?

Answer 3

A haem group - contains ferrous (Fe2+ ion)

Question 4

What can each ferrous ion in haemoglobin bind with?

Answer 4

One oxygen molecule, so one haemoglobin can carry 4 oxygen molecules in humans

Question 5

What is the equation for the formation of oxyhemoglobin?

Answer 5

Hb + 4O2 = HbO8

Question 6

What is the process by which haemoglobin binds with oxygen called?

Answer 6

Loading or associating
Happens in lungs

Question 7

What is the process by which haemoglobin releases oxygen called?

Answer 7

Unloading or disassociating
Happens in tissues

Question 8

To be efficient at transporting oxygen, what must haemoglobin do?

Answer 8

• Readily associate with oxygen at the surface where gas exchange takes place
• readily dissociate from oxygen at the tissues requiring it

Question 9

What is the property of haemoglobin that makes it efficient?

Answer 9

It changes its affinity(chemical attraction) for oxygen under different conditions

Question 10

How can haemoglobin change its affinity?

Answer 10

Its shape changes in the presence of certain substances e.g. co2

Question 11

How does the shape of haemoglobin change in the presence of CO2?

Answer 11

The new shape binds more loosely to oxygen and so it releases it - has a lower affinity

Question 12

Why are there different haemoglobin?

Answer 12

Each species produces a haemoglobin with a slightly different amino acid sequence and so different tertiary and quaternary structure and so different oxygen binding properties

Question 13

What happens when haemoglobin is exposed to different partial pressures of oxygen?

Answer 13

It does not bind to oxygen evenly

Question 14

What does the initial shape of the haemoglobin make it difficult to do?

Answer 14

For the first oxygen to bind to one of the sites on its 4 polypeptide units as they are closely united

Question 15

What happens at low oxygen concentrations?

Answer 15

Little oxygen binds to haemoglobin (on oxygen dissociation curve, shallow gradient initially)

Question 16

What happens to the shape of the haemoglobin after the 1st oxygen binds?

Answer 16

Quaternary structure changes, causing it to change shape

Question 17

How does the change of the quaternary structure of haemoglobin after the binding of the 1st oxygen aid the binding of the other oxygens?

Answer 17

The binding of the first oxygen induces the other subunits to bind to an oxygen

Question 18

What does the changing of the quaternary structure of the haemoglobin after the binding of the 1st oxygen mean?

Answer 18

It takes a smaller increase in partial pressure of oxygen to bind the 2nd oxygen than it did to bind the 1st one - known as positive cooperatively (gradient steepens)

Question 19

What happens after the binding of the 3rd oxygen molecule to haemoglobin?

Answer 19

• Harder for 4th one to bind due to probability
• Majority of binding sites occupied
• Less likely that a single oxygen will find an empty site
• Gradient of curve reduces and flattens off

Question 20

What is the affinity of haemoglobin like to the left of the curve?

Answer 20

Greater and vice versa

Question 21

What is the Bohr effect?

Answer 21

The greater the concentration of CO2, the more readily haemoglobin releases oxygen

Question 22

At the gas exchange-surface, what is the concentration of CO2 like?

Answer 22

Low

Question 23

What happens given that the concentration of CO2 is low at the gas exchange surface?

Answer 23

• Affinity of haemoglobin for O2 increases
• High concentration of O2 in lungs
• Both ensure that O2 is readily loaded by haemoglobin
• Oxygen disassociation graph shifted to left

Question 24

What is the concentration of CO2 like in rapidly respiring tissues?

Answer 24

High

Question 25

What happens given that the concentration of CO2 is high in rapidly respiring tissues?

Answer 25

- Affinity for O2 reduced - Low concentration of O2 - Both ensure O2 is readily unloaded from haemoglobin to cells - Oxygen disassociation graph shifted to right

Question 26

Why at greater concentrations of carbon dioxide do the haemoglobin more readily release its oxygen?

Answer 26

Dissolved CO2 is acidic and low pH causes haemoglobin to change its shape

Question 27

What is constantly being removed at the gas exchange surface and how does this affect the pH?

Answer 27

Carbon dioxide - pH slightly raised due to low concentration of this

Question 28

How does a higher pH affect the shape of haemoglobin?

Answer 28

It changes the shape into one that enables it to load oxygen readily

Question 29

How does a higher pH affect the affinity of haemoglobin for oxygen?

Answer 29

Increases it so oxygen is not released while being transported in the blood

Question 30

What is produced in the tissues and how does this affect the pH?

Answer 30

Carbon dioxide - given that it is acidic in solution, pH of blood within tissues is lowered

Question 31

How does a lower pH affect the shape of haemoglobin?

Answer 31

Changes the shape into one with a lower affinity for oxygen so it releases its oxygen to the respiring tissues

Question 32

What does a more active tissue mean?

Answer 32

More CO2 produced, so lower pH, so greater shape change, so more oxygen unloaded and used for respiration

Question 33

In practice, are all haemoglobin molecules loaded with their maximum 4 oxygen molecules?

Answer 33

No - overall saturation of haemoglobin at atmospheric pressure is normally around 97%

Question 34

What happens when haemoglobin reaches a tissue with a low respiratory rate?

Answer 34

Only one of the oxygen molecules will normally be released - so blood returning to lungs will contain haemoglobin that is 75% saturated

Question 35

How are many animals adapted to their environment?

Answer 35

By possessing different types of haemoglobin with different oxygen transport properties

Question 36

Does 1 risk factor cause cardiovascular disease?

Answer 36

No - only increases risk Combined together, 4 or 5 produce a disproportionately greater risk

Question 37

How many more times are smokers more likely to suffer from heart disease than non-smokers?

Answer 37

2x and 6x

Question 38

What are the two constituents of tobacco smoke that increase the likelihood of heart disease?

Answer 38

Carbon monoxide and nicotine

Question 39

How does carbon monoxide reduce oxygen carrying capacity of blood?

Answer 39

It binds easily, but irreversibly with haemoglobin to form carboxyhemoglobin

Question 40

What does the heart do given that carbon monoxide binds to haemoglobin?

Answer 40

- Works harder to supply equivalent quantity of oxygen to tissues - Can lead to raised blood pressure - This increases risk of CHD and strokes

Question 41

What does a reduction in the oxygen carrying capacity of blood due to carbon monoxide mean for the heart?

Answer 41

May be insufficient to supply the heart muscle with oxygen during exercise Can lead to chest pain(angina) or myocardial infarction

Question 42

What does nicotine stimulate the production of?

Answer 42

The hormone adrenaline, which increases heart rate and blood pressure - so greater risk of smokers suffering CHD or a stroke

Question 43

What does nicotine do to the platelets in the blood?

Answer 43

Makes them 'stickier'

Question 44

What happens if the platelets are 'stickier'?

Answer 44

Leads to a higher risk of thrombosis

Question 45

What is thrombosis?

Answer 45

Formation of a blood clot inside a blood vessel

Question 46

What can thrombosis lead to?

Answer 46

Strokes or myocardial infarction

Question 47

What can cause high blood pressure, in terms of the person?

Answer 47

Genes Excessive prolonged stress Certain diets Lack of exercise

Question 48

What must the heart do given that there is already a higher blood pressure within the arteries due to high blood pressure?

Answer 48

Work harder to pump blood into them and so more prone to failure

Question 49

What does a high blood pressure in the arteries mean for the arteries?

Answer 49

More likely to develop an aneurysm and burst, causing haemorrhage

Question 50

What is an aneurysm?

Answer 50

Weakening of the wall

Question 51

What do arteries do to resist the higher blood pressure within them?

Answer 51

The walls tend to become thickened and may harden, restricting flow of blood

Question 52

What are the 2 main types of blood cholesterol?

Answer 52

High-density lipoproteins (HDLs) Low-density lipoproteins (LDLs)

Question 53

What do HDLs do?

Answer 53

Remove cholesterol from tissues and transport it to liver for excretion Protect arteries against heart disease

Question 54

What do LDLs do?

Answer 54

Transport cholesterol from liver to tissues Infiltrate artery walls, leading to development of atheroma, which may lead to heart disease

Question 55

What do high levels of salt do to blood pressure?

Answer 55

Raise it

Question 56

What do high levels of saturated fat do to the body?

Answer 56

Increase LDLs and so blood cholesterol concentration

Question 57

Which foods reduce risk of heart disease?

Answer 57

Antioxidants (Vitamin C) Non-starch polysaccharide (dietary fibre)

Question 58

What is atheroma?

Answer 58

Abnormal build up of material in the inner layer of the arterial wall

Question 59

What does alcohol due to blood flow?

Answer 59

Decreases it to the muscles, can lead to CHD

Question 60

What does alcohol do to blood pressure?

Answer 60

Increases it by constricting arteries

Question 61

How does alcohol affect the rhythm of the heart?

Answer 61

Can lead to arrhythmia