animal transport (new).

Question 1

Explain the carriage of carbon dioxide / the Bohr effect?

Answer 1

• Carbon dioxide diffuses out of the tissue cells (produced in respiration), and enters red blood cells.
• Combines with water to form carbonic acid.
• Catalysed by the enzyme carbonic anhydrase.
• Carbon acid disassociates to form hydrogen ions and carbonate ions.
• Increase in hydrogen ions causes oxyhaemoglobin to unload its oxygen so oxygen is released to tissues for aerobic respiration.
• Hydrogen ions bond with haemoglobin to form haemoglobin acid - help to maintain pH of red blood cells.
• Haemoglobin acting as buffer.
• Hydrogencarbonate ions diffuse out of red blood cell into plasma.
• Causes an increase in charge of the red blood cell.
• Chloride ions move into the red blood cell to maintain charge. This is called the chloride shift.

Question 2

Define tissue fluid?

Answer 2

The fluid that cells are soaked in to facilitate substance exchange between cells and blood.

Question 3

Define oncotic pressure?

Answer 3

• Tendency of water to move into the blood by osmosis.
• Generated by plasma proteins.
• -3.3kPa

Question 4

What is the blood composed of?

Answer 4

Red blood cells (erythrocytes), white blood cells (neutrophils), platelets and plasma (contains plasma proteins).

Question 5

Function of plasma proteins?

Answer 5

• Lowers water potential in blood.
• Water wants to move into blood.
• Creates osmotic effect (osmosis can occur).
• Generates oncotic pressure.
• Big, cannot leave bloodstream, oncotic pressure will stay the same (-3.3kPa)

Question 6

What does -/+ pressure of substances mean?

Answer 6

• Positive = move out of blood.
• Negative = move into blood.

Question 7

Define hydrostatic pressure?

Answer 7

• Pressure generated by heart contraction.
• Changes according to location:
• Arterial end = +4.6kPa
• Venous end = +2.3kPa

Question 8

How does plasma move out of the capillaries?

Answer 8

• Through the arterial end.
• Higher hydrostatic pressure pushing out than oncotic pressure pushing in.
• Positive filtration pressure.
• Net fluid out.
• Plasma containing oxygen and nutrients forms tissue fluid, allowing nutrients to diffuse into cells.

Question 9

How does fuid move into the capillaries?

Answer 9

• Through the venous end.
• Higher oncotic pressure pushing in, than hydrostatic pressure pushing out.
• Negative filtration pressure.
• Net fluid in.
• Tissue fluid now containing carbon dioxide or urea brings it back into the blood, allowing it to be transported away.

Question 10

Structure of haemoglobin?

Answer 10

• Large globular conjugated protein.
• 4 subunits: 2 alpha, 2 beta.
• Each subunit has 1 haem group containing iron, which can bind to 1 oxygen molecule.

Question 11

What is positive cooperativity / conformational change?

Answer 11

• Binding of first oxygen molecule to first haem group changes shape of haemoglobin.
• Increases affinity for oxygen.
• Reversible as oxygen is released into tissues.

Question 12

Explain the conformational change of haemoglobin?

Answer 12

• Oxygen binds to first haem subunit.
• 25% saturated.
• Changes shape of subunits 2 and 3, giving them a higher affinity for oxygen.
• Can bind to oxygen easier, second oxygen molecule binds to second subunit.
• 50% saturated.
• Third molecule can bind even easier to third subunit.
• 75% saturated.
• Fourth oxygen is harder to bind to subunit due to high oxygen saturation.

Question 13

What are the X and Y axis of an oxygen dissociation curve?

Answer 13

X = Partial pressure of oxygen
Y = Oxygen saturation OR haemoglobin’s affinity for oxygen.

Question 14

What is partial pressure of oxygen?

Answer 14

Concentration of oxygen within a mixture of gases.

Question 15

Explain a low partial pressure of oxygen on an oxygen dissociation curve?

Answer 15

• Low affinity.
• Little haem group bound with oxygen.

Question 16

Explain a higher partial pressure of oxygen on an oxygen dissociation curve?

Answer 16

• Higher affinity.
• More Hb bing to oxygen.
• Becomes easier to bind to other oxygen (conformational change).

Question 17

Explain a very high partial pressure of oxygen on an oxygen dissociation curve?

Answer 17

• Hb becomes saturated.
• Becomes oxyhaemoglobin.

Question 18

What is the Bohr effect?

Answer 18

• Oxygen dissociation curve shifts to the right.
• Oxyhaemoglobin releases oxygen more readily at areas of high carbon dioxide.
• Low carbon dioxide conc. = lungs.
• High carbon dioxide conc. = tissues.

Question 19

Explain Hb’s affinity for oxygen at tissues/organs?

Answer 19

• Lower affinity for oxygen.
• Higher carbon dioxide conc.
• Release oxygen more readily (for more aerobic respiration).

Question 20

Explain Hb’s affinity for oxygen at lungs?

Answer 20

• Higher affinity for oxygen.
• Releases oxygen less readily.

Question 21

How does a foetal Hb oxygen dissociation curve compare to adult Hb?

Answer 21

• Shifts to the left.
• Foetal Hb has a higher affinity for oxygen.