Transport of gases

Question 1

• What is blood?

- Give 2 functions of blood

Answer 1

• Blood is an aqueous medium

- Allows for gas exchange and the delivery of important molecules such as glucose and oxygen

Question 2

• Why is blood a tissue ? (What cells is it made up of)

Answer 2

• Blood is a tissue comprising blood cells suspended in a straw-coloured fluid called plasma.
• Red blood cells, White blood cells and Platelets

Question 3

• What does Plasma contain?
• Plasma is 90% of what?
• What other materials does it transport around the body?
• What does it distribute around the body?

Answer 3

• Plasma contains digested food products e.g.: glucose. amino acids
• Plasma is 90% water
• Also transports: hormones, antibodies and other proteins
• It distributes heat around the body

Question 4

State the 3 types of blood cells (scientific terms)

Answer 4

1- Leucocytes (White Blood cells)
2- Thrombocytes (Platelets)
3. Erythrocytes (red blood cells)

Question 5

• Granulocytes and Agranulocytes are what type of what blood cell?
• What organelles do Granulocytes have and state their function
• What organelles do Agranulocytes have and state their function
• What kind of cells are Granulocytes and Agranulocytes

Answer 5

• They are Leucocytes (White blood cells)
• Granulocytes have granular cytoplasm and lobed nuclei and their function is to engulf pathogens by phagocytosis
• Agranulocytes have clear cytoplasm and spherical nucleus and their function is to produce antibodies and antitoxins
• They are both immune cells

Question 6

What is the function of a Thrombocyte and what is a Thrombocyte?

Answer 6

Thrombocytes are platelets which are involved in blood clotting.

Question 7

• What pigment makes up Erythrocytes?

- List their three important features which allows them to efficiently transport oxygen

Answer 7

• Haemoglobin pigment (Hb) make up Erythrocytes
• Flattened bio-concave disc shape - ensures large surface area to volume ratio for efficient gas exchange
• No nucleus or organelles - Maximises space for haemoglobin so more oxygen can be transported
• Diameter (6-8 ym) larger than capillary diameter - Slows blood flow to enable diffusion of oxygen, They are flexible so they can fit through the very narrow lumen of the capillaries

Question 8

• Describe the structure of Haemoglobin (what kind of protein, structure type, number and structure of polypeptide chains)
• Where is the Haem group located and what does it contain?
• Each Haem group is a binding site for how many oxygen molecules?
• One molecule of Haemoglobin is able to bind to how many molecules of oxygen and what does this form?

Answer 8

• Haemoglobin is a complex globular protein, with a quaternary structure consisting of four folded polypeptide chains.
• At the centre of each Polypeptide is a Haem group which contains iron (Fe 2+)
• Each Haem group is a binding site for one oxygen molecule
• One molecule of Haemoglobin is able to bind to four molecules of oxygen to form oxyhaemoglobin.

Question 9

• What intermolecular bonds can be found in haemoglobin?

- The reaction between oxygen and haemoglobin is what and give a balanced equation.

Answer 9

• Haemoglobin contains Hydrogen, Ionic and Disulphide bonds
• The reaction between Haemoglobin and Oxygen is reversible
• Hb + 4O2 —- HbO8

Question 10

Define these terms:
1- Affinity
2-Saturation
3-Association / Loading
4- Dissociation / Unloading

Answer 10

1- The degree to which one molecule (Haemoglobin)is chemically attracted to another molecule (oxygen)
2- The percentage of oxygen bound to haemoglobin
3- The uptake of oxygen by haemoglobin to form oxyhaemoglobin at the lungs
4- The release of oxygen at respiring tissues to form Haemoglobin

Question 11

• What is oxygen concentration measured in?
• When the partial pressure of oxygen is high (e.g in the lungs) what happens to haemoglobin and oxygen and what is formed.
• When the partial pressure of oxygen is low (e.g. in the respiring tissues) what happens to haemoglobin and oxygen and what product is formed

Answer 11

• Oxygen is measured by Partial pressure (kPa)
• When the partial pressure of oxygen is high haemoglobin has a high affinity for oxygen so oxygen associates with haemoglobin to form oxyhaemoglobin.
• When the partial pressure of oxygen low, haemoglobin has a low affinity for oxygen so oxygen dissociates from oxyhaemoglobin forming haemoglobin.

Question 12

• What is cooperative binding?

- Describe and explain the association of the first, second third and fourth molecule of oxygen with haemoglobin.

Answer 12

• Cooperative binding describes the ease with which a haemoglobin molecule binds to a second and then third oxygen molecules compared to the first and fourth molecule
• As Haemoglobin is a protein any molecules that associates with it will cause a slight change in shape. Once the first molecule of O2 has associated with haemoglobin it causes a slight change in shape that makes the second and third binding site more available, increasing haemoglobin affinity for oxygen. It is then more difficult for an oxygen molecule to associate with the last binding site.

Question 13

• What is a pulse oximeter used for
• How does it carry out this function
• Why is the oxygen saturation of a healthy person never 100%?

Answer 13

• A pulse oximeter estimates the oxygen saturation in your blood
• It does so by sending infrared light into the capillaries in your finger and then it measures how much light is reflected off the gases
• Some oxygen is used by the respiring cells of the alveoli
• The rate of blood flow through the pulmonary capillaries is still too fast for oxygen to diffuse into the blood.

Question 14

• Where is a foetal haemoglobin oxygen dissociation curve shifted to alongside an adult curve?
• What does this mean?

Answer 14

• Foetal Haemoglobin has an oxygen dissociation curve shifted to the left of an adult curve
• This means is has a higher affinity for oxygen and can therefore load oxygen from the mothers blood at all partial pressures of oxygen.

Question 15

Give 2 reasons why a baby doesn’t retain its foetal haemoglobin once it is born?

Answer 15

• Foetal haemoglobin has a higher oxygen affinity so not enough oxygen would be released to respiring tissue of an adult.
• If baby is female, when having own children, the adult needs its haemoglobin to have lower affinity than the foetal Haemoglobin

Question 16

• Where do Llamas live and give a consequence of this relating to partial pressure of oxygen
• How does a Llama compensate for this and where is the curve shifted

Answer 16

• Llamas live at high altitudes, with an increase in altitude, there is a drop in atmospheric pressure (not much gas oxygen in the atmosphere) therefore a reduction in the partial pressure of oxygen
• Llama’s haemoglobin has a higher affinity for oxygen and therefore picks up oxygen more readily at the lungs
• Curve is shifted to the left.

Question 17

• Why do animals living in high altitudes have more red blood cells?
• Suggest one change which could be observed in the blood of an athlete who had been training at high altitude

Answer 17

• More haemoglobin so more oxygen can be loaded and transported
• They would have more red blood cells

Question 18

• Where do Lugworms live?
• How do they absorb oxygen and from where?
• How do they cope with the low oxygen concentration of Seawater?
• Where is the curve shifted?

Answer 18

• Lugworms live in burrows in the sand on the seashore
• They absorb oxygen from the seawater they pump through their burrows
• They have a dissociation curve shifted to the left so a higher affinity for oxygen - so the haemoglobin more readily takes up oxygen

Question 19

• What kind of protein is myoglobin?
• What does it act as?
• Where is Myoglobin’s Dissociation curve located compared to that of haemoglobin.
• At every partial pressure of oxygen, how is myoglobin different to haemoglobin
• What does oxymyoglobin do if partial pressure becomes very low?
• What could cause the ppO2 to become very low?

Answer 19

• Myoglobin is a tertiary structured protein that is more stable than haemoglobin
• It acts as an oxygen store in muscle tissue .
• Myoglobin’s dissociation curve is very far to the left of haemoglobin.
• Myoglobin has a higher percentage oxygen saturation than haemoglobin
• Oxymyoglobin unloads its oxygen
• Vigorous excercise

Question 20

• What happens to the conditions when partial pressure of Carbon Dioxide is high?
• Where is Carbon dioxide produced (Give an example)
• What effect does this have on Haemoglobin i.e. its shape and affinity for oxygen
• Which Direction is the S-shaped curve shifted to
• What is this effect called

Answer 20

• When the partial pressure of CO2 is high conditions become more acidic
• Carbon dioxide is produced in respiring cell, e.g. contracting muscle
• This causes the haemoglobin to change shape slightly and so haemoglobin now has a lower affinity for oxygen, unloading this oxygen to the respiring tissues more readily.
• The S-shaped curve is shifted to the right
• This is the Bohr Effect

Question 21

Three ways in which CO2 is transported to the lungs for secretion

• What percentage of CO2 binds to haemoglobin and what is it transported as
• What percentage of CO2 is dissolved in Plasma
• What is the remaining percentage of CO2, what is it converted to and what is it transported in?

Answer 21

• 10% binds to haemoglobin and is transported as carbamino-Haemoglobin
• 5% is dissolved in Plasma
• 85% of the CO2 in the blood is converted to hydrogen carbonate ions (HCO3-) and is transported in Plasma.

Question 22

• How is Carbonic acid produced and what enzyme catalyses this reaction?
• What two ions does the Carbonic acid dissociate into?
• Describe what the HCO3- ion does
• Explain why and when do Chloride ions enter red blood cells - What is this known as
• Explain what the other ion does + Describe how oxygen is released from haemoglobin molecule
• What does the released oxygen then do?

Answer 22

• CO2 reacts with water to produce carbonic acid. This reaction is catalysed by the enzyme carbonic anhydrase
• Carbonic ions then dissociate into H+ and HCO3- ions (Hydrogen Carbonate ions)
• The HCO3- ions diffuse down their concentration gradient into plasma, they then combine with Na+ ions in plasma to form sodium Hydrogen Carbonate (NaHCO3)
• Cl- ions move into the red blood cell from the plasma by facilitated diffusion to maintain the electrical neutrality of the red blood cells and is known as the chloride shift.
• The H+ ions accumulate in the red blood cell and cause the pH to fall (blood becomes more acidic), this alters the haemoglobin reducing its affinity for oxygen. H+ combines with haemoglobin to haemoglobinic acid (HHb) which releases the oxygen
• The released oxygen then diffuses out of the red blood cells into the respiring tissues.

Question 23

• ## Describe and explain the link between Transport of CO2 and the Bohr Effect

Answer 23

• The high concentration of CO2 produced by actively respiring tissues reduces the affinity of haemoglobin for oxygen and therefore enables cells requiring more oxygen to obtain it by promoting the dissociation of oxygen from oxyhaemoglobin in the red blood cells.
• the more carbon dioxide produced, the more acidic the conditions will be and so more oxygen will dissociate from the oxyhaemoglobin.

Question 24

List 3 ways in how capillaries are adapted for their function of gas exchange

Answer 24

• Thin - one cell thick- shorter diffusion pathway
• Large Cross - Sectional area for exchange of materials
• Blood flows slowly through capillaries allowing time for exchange of materials.

Question 25

• What is tissue fluid?
• State two functions of tissue fluid.
• List 3 molecules required by cells and how they enter cells
• List 2 waste substances removed from the cell and how they are removed from the cell

Answer 25

• Tissue fluid is fluid in tissues which is plasma minus the plasma proteins.
• Tissue fluid bathes the cells and allows for the exchange of molecules, Removal of waste products
• Glucose, amino acids and oxygen are required by cells and diffuse into cells from tissue fluid
• Carbon dioxide and urea are waste substances removed from cell by diffusing out of cell into tissue fluid

Question 26

Tissue Fluid Formation

• Describe and explain what happens at the arterial end of the capillary - the pressures involved and the net flow.

Answer 26

• There is high hydrostatic pressure at the arterial end of the capillary because of contractions of the left ventricle, which forces fluid through gaps in the capillary walls
• The outward flow of fluid is opposed by osmotic pressure
• However the hydrostatic pressure is greater than the osmotic pressure therefore there is a net flow of fluid out of the blood
• Molecules dissolved in the tissue fluid then move by diffusion and facilitated diffusion into the cells

Question 27

Tissue Fluid formation

• Describe and explain what happens at the venous end of the capillary - the pressures involved and the net flow
• Why is there low hydrostatic pressure
• Describe the mechanism by which materials pass from the tissue fluid into the capillaries
• Approximately what percentage of tissue fluid flows back into capillaries

Answer 27

• Tissue fluid contains waste substances that have diffused out of cells. These can diffuse back into the blood in the capillaries down a concentration gradient
• There is now lower hydrostatic pressure because due to friction between the blood and the capillary wall and due to the lower volume of fluid in the capillaries
• Water potential in the blood is lowered due to the presence of plasma proteins, Osmotic pressure is now greater than hydrostatic pressure so there is now a net movement of water back into the blood by osmosis
• Approximately 90% of tissue fluid flows back into capillaries

Question 28

• Name a substance found in the plasma that helps to maintain the osmotic pressure
• Which system is the lymphatic system a part of?
• What percentage of of tissue fluid does not return to the capillaries and what happens to the remaining fluid

Answer 28

• Plasma proteins help to maintain the osmotic pressure
• It is part of the immune system
• Around 10% of tissue fluid does not return to the capillaries at the venous end and drains into lymphatic capillaries

Question 29

• What is the remaining fluid called and what is it?
• State two functions of the lymphatic system
• Explain why a low protein diet will result in fluid retention in tissues (4 bullet points)

Answer 29

• It is called lymph - it is fluid from tissues which does not drain back into the capillaries of the circulatory system
• The absorption of lipids in the small intestine and the formation of lymphocytes and the prevention of disease
• Less protein in diet means less plasma proteins in blood
• Water potential of the blood plasma is raised
• This reduces the water potential gradient (hydrostatic pressure is greater than osmotic pressure)
• So less water is reabsorbed by osmosis