3.3.4: Mass transport in animals

Question 1

Describe why Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.

Answer 1

1. Binding of first oxygen changes tertiary /
   quaternary (structure) of haemoglobin;
   Ignore ref. to ‘positive cooperativity’ unqualified
   Ignore ref. to named bonds
   Accept conformational shift caused
2. Creates / leads to / uncovers second / another
   binding site OR
   Uncovers another iron / Fe / haem group to bind to;

Question 2

Explain how
changes in the
shape of
haemoglobin result
in the S-shaped
(sigmoid)
oxyhaemoglobin
dissociation curve
(2)

Answer 2

1. First oxygen binds (to Hb) causing change in shape;
2. (Shape change of Hb) allows more O2 to bind (easily)
   / greater saturation with O2
   OR
   Cooperative binding;

Question 3

Haemoglobin is a
protein with a
quaternary structure.
Explain the meaning
of quaternary
structure (1).

Answer 3

(Molecule contains) more than one polypeptide (chain)

Question 4

Describe the
advantage of the
Bohr effect during
intense exercise. (2)

Answer 4

1. Increases dissociation of oxygen;
   Accept unloading/ release/reduced affinity for
   dissociation
2. For aerobic respiration at the tissues/muscles/cells
   OR
   Anaerobic respiration delayed at the
   tissues/muscles/cells
   OR
   Less lactate at the tissues/muscles/cells;

Question 5

Describe and
explain the effect of
increasing carbon
dioxide
concentration on the
dissociation of
oxyhaemoglobin. (2)

Answer 5

1. Increases/more oxygen dissociation/unloading
   OR
   Deceases haemoglobin’s affinity for O2;
   Accept more readily
   Accept releases more O2
2. (By) decreasing (blood) pH/increasing acidity;

Question 6

Explain why haemoglobin curve shifts left when diving (2)

Answer 6

1. High(er) affinity for O2 (than haemoglobin)
   OR
   Dissociates oxygen less readily
   OR
   Associates more readily;
   Accept holds O2 at lower ppO2
2. Allows (aerobic) respiration when diving/at low(er)
   pO2
   OR
   Provides oxygen when haemoglobin unloaded
   OR
   Delays anaerobic respiration/lactate production;

Question 7

Haemoglobin – Animals living at high altitudes shift to left (3)

Answer 7

1. high altitudes have a low partial pressure of O2;
2. high saturation/affinity of Hb with O2 (at low partial
   pressure O2);
3. sufficient/enough O2 supplied to respiring cells /
   tissues;

Question 8

why does the haemoglobin curve of small animals curve to the right (2)

Answer 8

1. Mouse haemoglobin/Hb has a lower affinity for
   oxygen
   OR
   For the same pO2 the mouse haemoglobin/Hb is less
   saturated
   OR
   At oxygen concentrations found in tissue
   mouse haemoglobin/Hb is less saturated;
   For ‘Hb is less saturated’ accept ‘less oxygen will be
   bound to Hb’.
2. More oxygen can be
   dissociated/released/unloaded (for metabolic
   reactions/respiration);
   Accept ‘oxygen
   dissociated/released/unloaded more readily/easily/quick
   ly’

Question 9

why does the haemoglobin curve curve to the right for more active animals
(2)

Answer 9

1. Curve to the right so lower affinity / % saturation
   (of haemoglobin);
2. Haemoglobin unloads / dissociates more readily;
3. More oxygen to cells / tissues / muscles;
4. For greater / more / faster respiration;

Question 10

Describe three control
measures the
student must use to
reduce the risks
associated with
carrying and using a
scalpel.

Answer 10

1. Carry with blade protected / in tray
2. Cut away from body;
3. Cut onto hard surface;
4. Use sharp blade;
5. Dispose of used scalpel (blade) as instructed;

Question 11

Describe Control measures when packing away (2)

Answer 11

1. Carry/wash sharp instruments by holding handle
   OR
   Carry/wash sharp instruments by pointing away (from
   body)/down;
   Accept for ‘instruments’, a suitable named example, eg.
   scalpel
2. Disinfect instruments/surfaces;
   Accept for ‘instruments’, a suitable named example, eg.
   scalpel
   Accept for ‘disinfect’, sanitise OR use antiseptic
3. Disinfect hands
   OR
   Wash hands with soap (and water);
   Accept for ‘disinfect’, sanitise OR use antiseptic
4. Put organ/gloves/paper towels in a (separate)
   bag/bin/tray to dispose;

Question 12

Give the pathway a
red blood cell takes
when travelling in
the human
circulatory system
from a kidney to the
lungs. (3)

Answer 12

1. Renal vein;
2. Vena cava to right atrium;
3. Right ventricle to pulmonary artery;

Question 13

Name the blood
vessels that carry
blood to the
heart muscle. (1)

Answer 13

Coronary arteries;

Question 14

what causes the semi-
lunar valve to close (1)

Answer 14

Because pressure in aorta higher than in ventricle;

Question 15

explain how the
atrioventricular valve
is closed (2)

Answer 15

1. ventricle contracts and volume decreases
2. pressure (ventricle) increases so higher than pressure
   of left atrium;

Question 16

Explain how an
arteriole can reduce
the blood flow into
capillaries. (2)

Answer 16

1. Muscle contracts;
2. Constricts/narrows arteriole/lumen;

Question 17

Describe Artery – Structure and
Function (5)

Answer 17

1. Elastic tissue to allow stretching/recoil/ smooths out
   flow of blood/maintains pressure;
2. (Elastic tissue) stretches when ventricles contract OR
   Recoils when ventricle relaxes;
3. Muscle for contraction/vasoconstriction;
4. Thick wall withstands pressure OR stop bursting;
5. Smooth endothelium reduces friction;

Question 18

Explain four ways in
which the structure
of the aorta is
related to its
function.

Answer 18

1. Elastic tissue to allow stretching / recoil /
   smoothes out flow of blood / maintains pressure;
2. (Elastic tissue) stretches when ventricles contract
   OR
   Recoils when ventricle relaxes;
3. Muscle for contraction / vasoconstriction;
4. Thick wall withstands pressure OR stop bursting;
5. Smooth endothelium reduces friction;
6. Aortic valve / semi-lunar valve prevents backflow.

Question 19

describe type of
circulation in fish (1)

Answer 19

1. Single circulatory system
   2 chambers/1 ventricle1 atrium
2. One vein carrying blood towards the heart/ One artery
   carrying blood away

Question 20

Explain how water from tissue fluid is returned to the circulatory system.
(4)

Answer 20

1. (Plasma) proteins remain;
   Accept albumin/globulins/fibrinogen for (plasma) protein
2. (Creates) water potential gradient OR
   Reduces water potential (of blood);
3. Water moves (to blood) by osmosis;
4. Returns (to blood) by lymphatic system;

Question 21

Explain
the role of the heart
in the formation of
tissue fluid. (2)

Answer 21

1. Contraction of ventricle(s) produces high blood /
   hydrostatic pressure;
2. (This) forces water (and some dissolved
   substances) out (of blood capillaries);

Question 22

High
absorption of salt
from the diet can
result in a higher
than normal
concentration of salt
in the blood plasma
entering capillaries.
This can lead to a
build-up of tissue
fluid.
Explain how. (4)

Answer 22

1. (Higher salt) results in lower water potential of
   tissue fluid;
2. (So) less water returns to capillary by osmosis (at
   venule end);
   OR
3. (Higher salt) results in higher blood pressure /
   volume;
4. (So) more fluid pushed / forced out (at arteriole
   end) of capillary;

Question 23

High
blood pressure
leads to an
accumulation of
tissue fluid. Explain
how. (2)

Answer 23

1. High blood pressure = high hydrostatic pressure;
2. Increases outward pressure from (arterial) end of
   capillary / reduces inward pressure at (venule) end of
   capillary;
3. (So) more tissue fluid formed / less tissue fluid is
   reabsorbed.

Question 24

Describe and explain Formation and
reabsorption (8)

Answer 24

1. At arteriole end high hydrostatic pressure/blood
   pressure;
2. Hydrostatic pressure higher than effect of osmosis;
3. Small molecules/named example eg glucose; water
4. Forces out;
5. Proteins remain in blood/ not removed as they are too
   large to leave capillary;
6. Increasing/giving higher concentration of blood
   proteins so proteins lower water potential of blood;
7. Water/fluid moves back into blood;
8. Water moves by osmosis