Kerboodle 8

Question 1

a the pull of water into venules due to the presence of albumin in blood plasma (1 mark)

Answer 1

oncotic pressure

Question 2

b a circulatory system where blood flows freely through body cavities (1 mark)

Answer 2

open (system)

Question 3

c the patch of tissue generating electrical impulses on the right atrium of the heart (1 mark)

Answer 3

sino-atrial node 

Question 4

d the negative ion produced by the dissociation of carbonic acid (1 mark)

Answer 4

hydrogen carbonate ion

Question 5

e the detachment of oxygen molecules from oxyhaemoglobin (1 mark)

Answer 5

dissociation 

Question 6

2 Explain the difference between:

a tissue fluid and lymph (2 marks)

Answer 6

tissue fluid is (plasma minus large proteins) in intercellular spaces  lymph has same composition but is enclosed in lymph vessels 

Question 7

2 Explain the difference between: b a single and a double circulatory system (2 marks)

Answer 7

n single system blood travels from heart to organs (including gills) and back to heart in one circuit  in double system blood goes from heart to lungs and back to heart, and then (second circuit) from heart to other organs 
B2

Question 8

2 Explain the difference between: c tachycardia and bradycardia. (2 marks)

Answer 8

tachycardia is fast heart rate (>100 bpm)  bradycardia is very low heart rate (<60 bpm)

Question 9

c The presence of carbon dioxide at respiring tissues increases the volume of oxygen offloaded by haemoglobin. This is called the Bohr effect or Bohr shift. Explain the molecular basis of the Bohr effect. (4 marks)

Answer 9

CO2 + H2O → carbonic acid (in red blood cells)  catalysed by carbonic anhydrase  carbonic acid dissociates to H+ + HCO3−  H+ bind to haemoglobin / form haemoglobinic acid  shape / binding ability of haemoglobin changed

Question 10

d Different species of mammals vary in the degree to which carbon dioxide increases oxygen unloading. For example, the Bohr effect is particularly large in seals that dive deep underwater for long periods of time, but it is small in hibernating hedgehogs. Suggest an explanation for the difference in magnitude of the Bohr effect in seals and hedgehogs. (4 marks)

Answer 10

seals: allows more oxygen carried by haemoglobin to be given up and used  detail re. aerobic respiration can continue so still possible for seal to get back to surface air  hedgehogs: low metabolic rate so little oxygen needed/little CO2 produced  oxygen freely available in air 

Question 11

iii Describe the mechanism that allows the ventricular systole stage in the ventricle to occur shortly after the atrial systole stage in the atria. (3 marks)

Answer 11

three from: electrical impulses from SAN (sino-atrial node) spread over atria  collagen fibres prevent excitation spreading to ventricles  AVN (atrio-ventricular node) is stimulated to generate impulses  these pass down Purkyne fibres to ventricles 

Question 12

iv Describe how a named piece of apparatus can be used to measure the length of stages atrial systole and . ventricular systole (4 marks)

Answer 12

four from: electrocardiograph / ECG machine  place electrodes on skin of chest  electrical changes detected and shown on trace  small/‘P’ wave shows contraction of atria  large / ‘QRS’ wave shows contraction of ventricles  idea of distance on trace / paper / ECG relates to time taken 
B4