(7) Mass transport

Question 1

what is the process by which haemoglobin binds with oxygen and where does it take place

Answer 1

loading/ associating and takes place in the lungs

Question 2

what is the process by which haemoglobin releases oxygen and where does this take place

Answer 2

unloading/ dissociating and takes place in the tissues

Question 3

what is the difference between haemoglobin with high/low affinity for oxygen

Answer 3

high affinity for oxygen takes up oxygen more easily but release it less easily. haemoglobin with low affinity for oxygen take up oxygen less easily but release it more easily

Question 4

what are 2 conditions for haemoglobin to be efficient

Answer 4

1) must readily associate with oxygen at the surface where gas exchange takes place (alveoli that have a high pO2)
2) readily dissociates from oxygen at the tissues requiring it
as these are contradictory- haemoglobin can change its affinity under different conditions

Question 5

what happens to haemoglobin in the presence of carbon dioxide

Answer 5

it changes shape and the new shaped molecule binds more loosely to oxygen meaning the haemoglobin releases its oxygen

Question 6

how many oxygen molecules can a haemoglobin molecule carry

Answer 6

4

Question 7

what is partial pressure of oxygen

Answer 7

a measure of oxygen concentration that is higher when there is a greater concentration of dissolved oxygen in cells

Question 8

how does oxygen partial pressure affect loading and unloading

Answer 8

a high pO2 means O2 loads onto haemoglobin to form oxyhaemoglobin and when there’s a low pO2, haemoglobin unloads it’s oxygen

Question 9

what conditions do tissues have that allow oxygen to be unloaded

Answer 9

they have a low pO2 due to the respiring cell using up oxygen which lowers pO2

Question 10

what does a dissociation curve show

Answer 10

how saturated the haemoglobin is with oxygen at any given partial pressure

Question 11

why is an oxygen dissociation curve S shaped

Answer 11

when Hb combines with the first O2 molecule its shape alters in a way that makes it easier for other molecules to join too. As the Hb starts to become saturated it gets harder for more O2 molecules to join

Question 12

what is the Bohr effect

Answer 12

haemoglobin gives up its oxygen more readily at higher partial pressures of CO2. respiring cells produce CO2 which increases the rate of O2 unloading so dissociation curve shifts right

Question 13

what is the circulatory system made up of

Answer 13

heart and blood vessels

Question 14

what are arteries

Answer 14

vessels that carry blood from the heart to the rest of the body. thick and muscular walls with elastic tissue to stretch and recoil as the heart beats to help it maintain high pressure. the endothelium is folded so artery can stretch. carry oxygenated blood

Question 15

what are arterioles

Answer 15

arteries divide into smaller vessels called arterioles. muscles in the arterioles direct blood to different areas of demand by contracting to restrict blood flow or relaxing to allow it

Question 16

what are veins

Answer 16

take blood back to heart under low pressure. wide lumen with little elastic or muscle tissue. contain valves to prevent backflow. carry deoxygenated blood

Question 17

what is the exception with pulmonary arteries and veins

Answer 17

pulmonary veins carry oxygenated blood to the heart from the lungs.
pulmonary arteries carry deoxygenated blood to the lungs

Question 18

what are capillaries

Answer 18

arterioles branch into capillaries (smallest blood vessel) they’re adapted for efficient diffusion as glucose and oxygen are exchanged between cells and capillaries. only one cell thick. large number of them to increase SA for exchange

Question 19

what is tissue fluid

Answer 19

fluid that surrounds tissue cells. made from small molecules that leave blood plasma eg O2, H2O and nutrients (doesn’t contain RBC’s or big proteins)

Question 20

in a capillary bed, how do substances move out of the capillaries and into the tissue fluid by pressure filtration

Answer 20

1) hydrostatic pressure in the capillaries is greater than in the tissue fluid at the start of the capillary bed
2) an overall outward pressure forces fluid out of the capillaries and into spaces around cells forming tissue fluid
3) hydrostatic pressure reduces in the capillaries (much lower at the venule end)
4) water potential at venule end is lower than in the tissue fluid due to fluid loss and ever increasing conc of plasma proteins
5) some water re enters capillaries from tissue fluid at venule end by osmosis

Question 21

what happens to excess tissue fluid

Answer 21

it is drained into the lymphatic system which transports it back into the circulatory system

Question 22

what are the roles of the left and right sides of the heart

Answer 22

right side- pumps deoxygenated blood to the lungs

left side- pumps oxygenated blood to the whole body

Question 23

difference between left and right sides of the heart

Answer 23

left ventricle has thicker and more muscular walls than the right ventricle because it needs to contract to pump blood around the whole body rather than just the lungs.

Question 24

why do the ventricles have thicker walls than the atria

Answer 24

ventricles have to push blood out of the heart whereas atria just push blood a short distance into the ventricles

Question 25

what do the atrioventricular valves do

Answer 25

link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract

Question 26

what do the semi lunar valves do

Answer 26

link the ventricles to the pulmonary artery and aorta and stop blood flowing back into the heart after the ventricles contract

Question 27

how do valves work

Answer 27

if theres higher pressure behind a valve it’s forced open but if the pressure is higher in front of the valve its forced shut so blood only flows in one direction through the heart

Question 28

describe the 3 stages of the cardiac cycle

Answer 28

1) ventricles relax, atria contract. chambers have decreased vol and increased pressure. blood is pushed into ventricles so slight increase in chamber vol and pressure
2) ventricles contract, atria relax- pressure is higher in ventricles than atria so AV valves shut to prevent backflow but SL valves open as pressure in ventricles is higher than in aorta and pulmonary arteries so blood is forced into these arteries
3) ventricles relax, atria relax- pressure increase in aorta and pulmonary artery closes SL valves to prevent backflow. blood returns to heart and atria refill, increases pressure. AV valves open as pressure falls, blood flows passively into ventricles

Question 29

atheroma formation is how most cardiovascular disease starts. how do atheroma’s form

Answer 29

damage occurs to the endothelium (due to high bp) WBC’s and lipids clump together and form fatty streaks. this builds up under the lining and forms a fibrous plaque (atheroma). this blocks the artery lumen and restricts blood flow, bp increases

Question 30

what is an aneurysm

Answer 30

atheroma plaque damages, weakens and narrows arteries- increases bp, when blood travels through a weak artery at high pressure it can push the inner layers of the artery through the outer elastic layer to form a balloon like swelling (aneurysm)

Question 31

what is thrombosis

Answer 31

atheroma plaque can rupture the endothelium of an artery leaving the artery wall rough. platelets and fibrin accumulate at the sight of damage and form a blood clot which can block the artery or come dislodged and block another vessel

Question 32

which blood vessel supplies the heart muscle with blood

Answer 32

coronary arteries

Question 33

how is a myocardial infarction (heart attack) caused

Answer 33

if a coronary artery becomes blocked then an area of heart muscle will be cut off from blood supply so will receive no oxygen

Question 34

why does high cholesterol increase risk of cardiovascular disease

Answer 34

cholesterol is one of the main constituents of the fatty deposits that form atheromas

Question 35

how does smoking cigarettes increase the risk of cardiovascular disease

Answer 35

nicotine increases risk of high bp
CO combines with haemoglobin and reduces the amount of oxygen transported in the blood and if heart muscle doesn’t get enough oxygen- heart attack
smoking also decreases amount of antioxidants in blood so cell damage in coronary artery walls is more likely and can lead to atheroma

Question 36

how does high blood pressure increase risk of cardiovascular disease

Answer 36

increases risk of damage to artery walls, damaged walls increase risk of atheroma formation which further increases blood pressure and can cause blood clots (blocks flow of blood)

Question 37

what is the role of xylem tissue

Answer 37

transports water and mineral ions in solution (move up the plant from the roots to the leaves)

Question 38

what is the role of the phloem tissue

Answer 38

transports organic substances like sugars in solution both up and down the plant

Question 39

what are xylem vessels

Answer 39

long, tube like structures formed from dead cells joined end to end

Question 40

how does water move up a plant against the force of gravity

Answer 40

water evaporates from leaves at the top of the xylem (transpiration). this creates tension which pulls more water into the leaf and as water molecules are cohesive, when some are pulled into the leaf, others follow

Question 41

4 factors that affect transpiration rate

Answer 41

light- (rate is faster in presence of light) stomata open when its light to get in CO2 for photosynthesis
temperature- (faster rate at higher temp) molecules have more energy so evaporate faster
humidity- faster rate when lower humidity- air is dry conc gradient between leaf and air increases
wind- faster rate if more windy- water molecules blown away from around stomata so conc gradient increases