3.3.4.1 mass transport in animals

Question 1

describe the structure of haemoglobin

Answer 1

globular protein, quaternary structure with 2 heavy and 2 light polypeptide chains, each chain has a haem group with a Fe2+ ion which carries the oxygen molecule

Question 2

how is oxygen loaded, transported and unloaded

Answer 2

1. partial pressure of oxygen is high in the lungs so oxygen binds to haemoglobin forming oxyhaemoglobin
   2.oxyhaemoglobin is transported in the blood in red blood cells
2. oxygen is unloaded to respiring cells at a low partial pressure of oxygen
3. unloading of oxygen occurs when there is a high CO2 concentration

Question 3

explain the oxygen dissociation curve

Answer 3

due to the shape of haemoglobin, it is difficult for the first oxygen molecule to bind to Hb
when Hb binds with the first molecule its shape changes making it easier for the next oxygen molecules to bind
as Hb becomes more saturated it is harder for more oxygen molecules to bind as there are less sites for the molecule to bind

Question 4

what is positive cooperativity

Answer 4

when a haemoglobin protein changes shape making it easier for the second and third molecule to bind

Question 5

describe the gradient of the oxygen dissociation curve

Answer 5

shallow gradient initially due to less oxygen binding
the gradient becomes steeper as more molecules bind to Hb
gradient becomes shallow again and flattens off as it is hard for oxygen to bind

Question 6

describe the effect of increasing carbon dioxide concentration on the oxygen dissociation curve.

Answer 6

increasing conc of CO2 causes the curve to shift to the right - the bohr effect-
increase conc, decreases pH in the blood, causing the shape of Hb to change, decreasing the affinity of oxygen, increasing rate of dissociation/ unloading of oxygen

Question 7

examples of left shift of the oxygen dissociation curve due to low oxygen

Answer 7

living in an environment with low partial pressure of oxygen ( e.g. high altitude, low altitude and foetuses) gives organisms a higher affinity for oxygen
so Hb associates with oxygen, allowing the Hb molecule to become fully saturated at a lower partial pressure

Question 8

what does a closed double circulatory system mean

Answer 8

closed - blood is confined to blood vessels
double - blood passes through the heart twice per cycle

Question 9

describe the structure of the heart

Answer 9

left and right atrium
left and right ventricle
atrio-ventricular valves
semi-lunar valves

Question 10

function and structure of atriums

Answer 10

thin walled + elastic
pump blood to the ventricles

Question 11

function and structure of ventricles

Answer 11

thick + muscular walls as they pump blood further
ventricles pump blood to the lungs and the body

Question 12

what is the systemic circulatory system and explain it

Answer 12

when blood is pumped to the rest of the body ( not the lungs).
oxygenated blood is pumped from the left ventricle out the aorta and to body tissues.
the aorta splits into the renal artery which passes blood to the kidneys.
the renal vein takes deoxygenated blood to the heart via the inferior vena cava

Question 13

what is the pulmonary circulatory system and explain it

Answer 13

when blood is pumped to the lungs via the pulmonary blood vessels.
deoxygenated blood is pumped from the right ventricle out the pulmonary artery to the lungs.
the oxygenated blood is sent back to the heart via the pulmonary vein

Question 14

describe the first stage of the cardiac cycle

Answer 14

Atrial systole
1. ventricles relax and the atria contracts
2. this decreases the volume of the chambers but increasing the pressure
3. this pushes blood into the ventricle opening the AV valve
4. this increases the volume and the pressure inside the ventricle

Question 15

describe the second stage of the cardiac cycle

Answer 15

ventricle systole
1. atria relaxes and the ventricle contracts decreasing their volume increasing their pressure
2. a higher pressure in the ventricle than the atria closes the AV valve (lub sound)
3. high pressure in the ventricle opens the SL valve forcing blood out the ventricle into the pulmonary artery and aorta

Question 16

describe the third stage of the cardiac cycle

Answer 16

atria and ventricle diastole
1. ventricle and atria both relax
2. higher pressure in the arteries close the SL valve (dub sound)
3.atria fills with blood due to higher pressure in the veins and therefore the atria.
4. pressure of the atria is greater than the pressure of the ventricle causing the AV valve to open allowing blood to flow passively into the ventricle, restarting the cycle

Question 17

structure of an artery + how its related to its function

Answer 17

thick muscle wall - due to high pressure
thick elastic tissue - allows them to stretch and recoil
smooth endothelium lining - reduces friction + maintains high blood pressure
narrow lumen

Question 18

what are arterioles

Answer 18

when arteries divide into smaller vessels
they control blood flow from the arteries to the capillaries
thick muscular layer to slow down blood flow

Question 19

structure of the vein + how its related to its function

Answer 19

thin muscle layer
thin elastic layer
wide lumen - maximise blood sent to heart
contains valves
low blood pressure

Question 20

structure of capillaries + how its related to its function

Answer 20

permeable walls - allow for gas exchange
one cell thick - short diffusion distance + slow blood flow to allow for diffusion

Question 21

what are capillary beds

Answer 21

network of capillaries

Question 22

what is tissue fluid

Answer 22

fluid that surround tissues, containing water, oxygen and nutrients

Question 23

how is tissue fluid formed

Answer 23

1. high hydrostatic pressure at the arterial end. this forces fluid out of the capillary
2. ultrafiltration of small molecules occurs
3. hydrostatic pressure in the capillary decreases at the venule end
4. proteins remaining in the capillary cause a decrease in water potential at the venule end
5. water re enters the capillaries via osmosis

Question 24

what happens to excess tissue fluid

Answer 24

drained into the lymphatic system then back to the circulatory system

Question 25

describe the composition of lymph

Answer 25

more lymphocytes and amino acids
less oxygen and nutrients

Question 26

formula for cardiac output

Answer 26

cardiac output = stroke volume X heart rate