Blood, Blood Clotting, Haemoglobin And Oxygen Dissociation Curves

Question 1

What is plasma?

Answer 1

The liquid component of blood which transports RBCs, amino acids and glucose, ions, CO2, urea, fibrinogen, prothrombin and clotting factors

Question 2

How are RBCs adapted for their function of transporting oxygen?

Answer 2

They contain the pigment haemoglobin for carrying oxygen.

They have no nucleus or organelles, to give more room for haemoglobin. Their biconcave shape gives them a large surface area to volume ratio for O2 transport and gas exchange.

Question 3

Describe polymorphs (microphages).

Answer 3

Small white blood cells with a multi-lobed nucleus and granular cytoplasm.

Question 4

What do polymorphs do?

Answer 4

Carry out phagocytosis: They engulf foreign material eg bacteria, encase it in a phagosome and digest it intracellularly using enzymes.

Question 5

Describe monocytes (macrophages).

Answer 5

Larger white blood cells with a bean-shaped nucleus and non-granular cytoplasm.

Question 6

What do monocytes do?

Answer 6

Carry out phagocytosis (for example, at the site of a wound).

Question 7

Describe lymphocytes.

Answer 7

White blood cells with a large, round nucleus and little cytoplasm.

Question 8

What do lymphocytes do?

Answer 8

B-lymphocytes produce antibodies that attack foreign antigens. T-lymphocytes attack and kill foreign antigens or infected cells.

Question 9

What are platelets?

Answer 9

Cell fragments involved in blood clotting and repairing minor damage to blood vessels.

Question 10

What is the importance of clotting?

Answer 10

1. It prevents entry of pathogens by sealing wounds.
2. It prevents too much loss of essential body fluid/plasma.

Question 11

What name is given to the type of reactions involved in blood clotting?

Answer 11

A cascade of reactions (meaning that certain compounds catalyse reactions which are on further down the chain).

Question 12

When platelets are activated by damage, what does this cause the release of and what must also be present for the cascade reactions to begin?

Answer 12

Clotting factors including thromboplastin are released. Calcium ions and Vitamin K must be present.

Question 13

What are thromboplastin, the clotting factors, calcium ions and vitamin K needed for?

Answer 13

Converting prothrombin to thrombin.

Question 14

What does thrombin do?

Answer 14

Catalyses the conversion of soluble fibrinogen to insoluble fibrin.

Question 15

What does fibrin form?

Answer 15

The fibrous strands of fibrin form a mesh that traps the RBCs, forming an insoluble clot.

Question 16

What is tissue fluid?

Answer 16

Tissue fluid is the fluid that surrounds capillaries and the cells of our tissues.

Question 17

What is tissue fluid made up of?

Answer 17

Plasma minus RBCs and proteins (i.e. it consists of water, ions, amino acids, glucose, CO2, urea).

Question 18

What is the main force driving the formation of tissue fluid?

Answer 18

A hydrostatic pressure, up, due to the narrowing of blood vessels pushes tissue fluid out through the capillary walls.

Question 19

What force draws tissue fluid back into the capillaries?

Answer 19

A lower a or more negative ws, in other words, an osmotic pressure, due to the presence of plasma proteins draws tissue fluid back into the capillaries.

Question 20

Why is tissue fluid formed at the arterial end of the blood capillaries?

Answer 20

At the arterial end, the hydrostatic pressure is greater than the osmotic pressure due to the lower water potential in the capillaries

Question 21

Why is tissue fluid drawn back in at the venous end of the capillaries?

Answer 21

At the venous end, the osmotic pressure due to the lower water potential in the capillaries is greater than the hydrostatic pressure.

Question 22

What happens if there is excess tissue fluid?

Answer 22

It is drained into the lymphatic system and becomes lymph.

Question 23

How is haemoglobin (Hb) a quaternary protein?

Answer 23

It consists of 4 polypeptide chains, 2 alpha-chains and 2 beta-chains.

Question 24

How is haemoglobin a conjugated protein?

Answer 24

At the centre of each polypeptide chain is a non-protein, iron-containing haem group (the prosthetic group).

Question 25

How many O2 molecules can each haemoglobin molecule carry?

Answer 25

Each haem group binds to one oxygen molecule, so therefore 4 oxygen molecules can be carried per haemoglobin molecule (one per polypeptide chain).

Question 26

What does haemoglobin (Hb) become when it has oxygen bound to it?

Answer 26

Oxyhaemoglobin.

Question 27

What is cooperative loading?

Answer 27

When one molecule of oxygen binds to a haem group, a conformational change takes place which facilitates the binding of a second oxygen molecule, leading to further structural changes that make it easier for the third one to bind and so on until all 4 are bound.

Question 28

What do we mean by the partial pressure of a gas?

Answer 28

Partial pressure of a gas is the proportion of the total air pressure that is due to that gas. It is often expressed as kPa.

Question 29

What do we mean by 'oxygen dissociation curve' for haemoglobin?

Answer 29

The oxygen dissociation curve is a graph that shows us the % saturation of Hb with oxygen at different partial pressures of oxygen.

Question 30

What does the oxygen dissociation curve tell us about what happens in the lungs?

Answer 30

In the lungs, where there is a higher partial pressure of oxygen, Hb has a higher affinity for oxygen, meaning it picks it up and becomes fully saturated.

Question 31

What does the oxygen dissociation curve tell us about what happens in exercising muscles?

Answer 31

In exercising muscles, where there is a very low partial pressure of oxygen, Hb has a much lower affinity for oxygen, meaning it releases its oxygen to the tissues and therefore has a low % saturation of oxygen itself.

Question 32

What is loading tension?

Answer 32

The partial pressure at which the haemoglobin is 95% saturated with O2.

Question 33

What is unloading tension?

Answer 33

The partial pressure at which the haemoglobin is 50% saturated with O2.

Question 34

What is the Bohr Effect?

Answer 34

The BOHR EFFECT describes the shifting of the oxygen dissociation curve to the right in higher carbon dioxide levels/high partial pressures of CO2 (high pCO2).

Question 35

What is the Bohr Shift?

Answer 35

During strenuous activity, the increased CO2 produced by muscles shifts the oxygen dissociation curve to the right, meaning that Hb releases its oxygen to the muscle cells more readily.

Question 36

What is myoglobin?

Answer 36

Myoglobin is a storage pigment for oxygen, found in our 'red' or skeletal muscles.

Question 37

Describe the structure of myoglobin.

Answer 37

Myoglobin consists of one polypeptide chain with a haem group in its centre. The haem group carries one oxygen molecule.

Question 38

What is the significance of the shape of the myoglobin dissociation curve?

Answer 38

Myoglobin only releases its oxygen when oxygen partial pressures are very low; otherwise, it remains fully saturated.

Question 39

What is the advantage to us of having myoglobin?

Answer 39

When our respiring muscles have run out of oxygen, myoglobin releases its oxygen store, enabling muscular contraction to continue aerobically, delaying the onset of anaerobic respiration

Question 40

What happens to the oxygen in the atmosphere at high altitudes?

Answer 40

There is less oxygen available (PO2 drops) in the atmosphere as height above sea level increases.

Question 41

How does the low oxygen availability affect us?

Answer 41

When PO2 decreases at high altitudes, it decreases the ability of our haemoglobin to fully saturate. This will cause altitude sickness and lack of energy.

Question 42

How do high altitude dwellers like Llamas cope with the problem of low PO2?

Answer 42

High altitude dwellers have specialised haemoglobin which becomes fully saturated at much lower PO2 values. This means that their oxygen dissociation curve for haemoglobin would sit to the LEFT of low level dwellers.

Question 43

What adaptations occur when someone moves from a low altitude to a high altitude?

Answer 43

The number of RBCs increases to increase the capacity for transporting as much of the available oxygen as possible to the cells. Ventilation rate increases to maximise the amount of oxygen diffusing from the alveoli into the capillaries during gas exchange.

Question 44

How have communities who have lived at high altitude for generations evolved?

Answer 44

Over many generations a special type of haemoglobin evolves that saturates at a lower PO2 level.