3b (more exchange/transport)

Question 1

what is haemoglobin?

Answer 1

a large protein with a quaternary structure (4 polypeptide chains)
each chain has a haem group which contains an iron ion

Question 2

what does affinity for oxygen mean?
how many oxygens can bind to haemoglobin?

Answer 2

tendency to combine with oxygen
4

Question 3

what is the reversable reaction for oxygen association and dissociation?

Answer 3

haemoglobin + oxygen <-> oxyhaemoglobin
(Hb+ 4O2<-> HbO8)

Question 4

what is partial pressure of oxygen/ CO2
(pO2) (pCO2)

Answer 4

measure of oxygen/ carbon dioxide concentration. greater conc of dissolved O2/ CO2 the higher the partial pressure

Question 5

what does affinity for oxygen depend on?

Answer 5

the partial pressure of oxygen
oxygen loads onto haemoglobin to form oxyhaemoglobin where theres a high pO2
oxyhaemoglobin unloads its oxygen where theres a lower pO2

Question 6

think of a question for this

Answer 6

O2 enters blood cappilaries at alveoli which have a high pO2 so O2 loads onto haemoglobin to form oxyhaemoglobin
when cells respire, they use up O2 which lowers the pO2. rbc deliver oxyhaemoglobin into respiring tissues where it unloads oxygen
haemoglobin then returns to lungs to pick up more O2

Question 7

what is is an oxygen dissociation curve?

Answer 7

shows how affinity for oxygen varies and how saturated haemoglobin is with oxygen at any partial pressure

Question 8

describe oxygen dissociation curve

Answer 8

see poster on it
1)tertiary structure quite tight so difficult for o2 to physically get in- hard for 1st o2 to associate- low affinity so gradient flat
2)1st o2 binding changes shape of quaternary structure so easier for other sub units to bind to o2 to gradient steeper
3)smaller increase in partial pressure needed for 2nd o2 to bind- positive cooperativity so gradient steepens
4)in theory, easy for 4th to bind but hard in practice as majorit of binding sites are occupied so less likely for o2 to find empty site- conc grad decreases

Question 9

what is the bohr effect?

Answer 9

haemoglobin gives up oxygen more readily at a higher pCO2
cells respire and produce CO2 so raise pCO2
increases rate of oxygen unloading so dissociation curve shifts right
saturation of blood with oxygen is lower for a given pO2 so more oxygen released
check book

Question 10

how does haemoglobin and dissociation curve change for different organisms

Answer 10

diff organism= diff type of haemoglobin= diff O2 transporting abilities
environment w low O2 conc- haemoglobin w higher affinity for O2 than humans so curve shifts left (lugworm left)
very active so have high O2 demand- haemoglobin w lower affinity for O2 than humans so curve shifts right

Question 11

what are the names of all the blood vessels entering and leaving the heart lungs and kidneys?

Answer 11

see page 74 of revision guide

Question 12

what does blood transport?

Answer 12

respiratory gases, products of digestion, metabolic waste and hormones

Question 13

why is the heart called a double circulatory system? what is the hearts blood supply called?

Answer 13

there are 2 circuits
one takes blood from the heart to the lungs and back to the heart and the other takes blood around the rest of the body
the left and right coronary arteries

Question 14

what are arteries?

Answer 14

blood vessels that carry blood away from the heart
thick muscular walls
elastic tissue to stretch and recoil to maintain pressure
endothelium (inner lining) is folded so artery can stretch maintaining high bp
all carry oxygenated blood apart from pulmonary artery

Question 15

what are arterioles?

Answer 15

arteries divide into smaller blood vessels which form a network
blood directed to diff areas of demand by muscles inside arterioles which contract to restrict the blood flow or relax to allow blood flow

Question 16

what are veins?
adaptations?
what do they carry?

Answer 16

blood vessels which carry blood to heart
wider lumen than arteries with very little elastic or muscle tissue
contain valves to prevent backflow
flow through veins helped by contraction of body muscles surrounding them
all carry deoxygenated blood except for pulmonary veins

Question 17

what are capillaries?
how are they adapted?

Answer 17

smallest blood vessel which arterioles branch into
substances exchanged between cells and capillaries so theyre adapted for efficient diffusion
-found very near cells in exchange tissues so short diffusion pathway
- walls one cell thick so short diffusion pathway
- lots of capillaries (form capillary bed) so large surface area

Question 18

what is tissue fluid?
what is it made from?
what is its role?

Answer 18

fluid that surrounds cells in tissues
made from small molecules that leave the blood plasma like water, oxygen, nutrients but not rbc or big proteins as they are too big to be pushed out of capillary walls
cells take in oxygen and nutrients from tissue fluid and release metabolic waste into it

Question 19

how is tissue fluid formed?

Answer 19

in capillary bed, substances move out of capillaries into tissue fluid by pressure filtration
1. at start of capillary bed, nearest arteries, hydrostatic pressure in cap is greater than tissue fluid
2. difference means overall outward pressure forces fluid out of capillaries and into spaces around cells forming tissue fluid
3. as fluid leaves, hydrostatic pressure reduces in capillaries so is lower at venule end
4. due to fluid loss and increasing conc of plasma proteins (which dont leave caps), the water pot at the venule end is lower than tissue fluid
5. so some water re-enters caps from tissue fluid at venule end by osmosis

Question 20

what happens to excess tissue fluid?

Answer 20

drained into lymphatic system which transports it from tissues and puts it back in circulatory system

Question 21

what can cause an accumulation of tissue fluid in the tissues?

Answer 21

high blood pressure as it creates a high hydrostatic pressure in the capillaries

Question 22

label a diagram of the heart
what does the right side pump?
what does the left side pump?

Answer 22

see poster
right- deoxygenated blood to lungs
left- oxygenated blood to whole body

Question 23

what does the left ventricle do?
how is it adapted?

Answer 23

thicker more muscular walls than right so it can contract powerfully enough to pump blood all the way around the body
right only needs to go to lungs

Question 24

why do ventricles have thicker walls than atria?

Answer 24

they have to push blood out of heart whereas atria just need to push blood into ventricles

Question 25

what are the AV valves?

Answer 25

link artery to ventricle and prevent backflow in atria when ventricles contract

Question 26

what are SL valves?

Answer 26

link ventricles to pulmonary artery and aorta and prevent backflow into heart after ventricles contract

Question 27

what do the cords do in the heart?

Answer 27

attach atrioventricular valves to pulmonary artery and aorta and stop blood flowing back into heart after ventricles contract

Question 28

when do valves open and close?

Answer 28

only open one way
higher pressure behind valve- forced open
higher pressure in front of valve- forced shut
means blood only flows one way through the heart

Question 29

what is the cardiac cycle?

Answer 29

ongoing sequence of contraction (systole) and relaxation (diastole) of the atria and ventricles that keeps blood continuously circulating

Question 30

what are the three simplified stages of the cardiac cycle?

Answer 30

1) atria systole
- ventricles relax and atria contract so decrease vol and increase press which pusses blood into ventricles. slight increase in ventricular pressure and chamber vol as ventricles receive blood from atria
2) ventricular systole
- atria relax and ventricles contract so decrease vol and increase press. press higher than atria so AV valve shuts. press in ventricles also higher than aorta/ pulmonary artery so SL valves open and blood forced into arteries
3) ventricular and atrial diastole
- ventricles and atria both relax. higher press in pulmonary artery and aorta closes SL valves to prevent bf. blood returns to heart and atria fill
again due to high pressure in vena cava and pulmonary vein. so, pressure in atria increases. ventricles continue to relax so pressure falls below pressure of atria so AV valves open and blood flows passively into ventricles. atria contract and cycle begins again

Question 31

How do you work out cardiac output?

Answer 31

heart rate x stroke volume

Question 32

explain the graph showing pressure in cardiac cycle

Answer 32

see poster

Question 33

what is digestion?

Answer 33

polymers being hydrolysed into monomers so that they are small enough to diffuse/ actively transport across a membrane to be absorbed into the blood

Question 34

what are carbohydrates broken down by?
where are these enzymes produced?

Answer 34

amylase- converts starch to maltose by hydrolysing glycosidic bonds
produced by salivary glands and pancreas

membrane bound disaccharidases- enzymes attached to cell membranes of epithelial cells lining the ileum. help breakdown disaccharides into monosaccharides by hydrolysing glycosidic bonds eg maltase, sucrase, lactase

Question 35

what are lipids broken down by?

Answer 35

lipase catalyses breakdown into fatty acids and monoglycerides
made in pancreas but used in small intestine

bile salts produced by liver- emulsify fats to increase sa

once broken down, monoglycerides and fatty acids and bile salts join to form micelles

Question 36

what are proteins broken down by?

Answer 36

endopeptidases- hydrolyse peptide bonds within protein, eg trypsin which is synthesised in pancreas and secreted in small intestine and pepsin which is released by into stomach by cells in stomach lining- only works in acidic cond hence hcl in stomach

exopeptidases- hydrolyses bonds at ends of protein molecules, remove single amino acid from proteins, dipeptidases are exopeptidases for dipeptides - separate the 2 amino acids by hydrolysing peptide bond, located in cell-surface membrane of epithelial cells

Question 37

way to remember what endopeptidases and exopeptidases do

Answer 37

enDopeptidases- break bonds insiDe protein

Question 38

how are monosaccharides absorbed?

Answer 38

glucose and galactose are absorbed by co-transport with sodium ions
fructose is absorbed via facilitated diffusion through a different transporter protein

Question 39

how are monoglycerides and fatty acids absorbed?

Answer 39

micelles help move monoglycerides and fatty acids to epithelium
because they constantly break up and reform, they can release monosaccharides and fatty acids allowing them to be absorbed
monoglycerides and fatty acids are lipid soluble so can diffuse directly across epithelial cell membrane

once inside, transported to er where they reassemble to triglycerides.
starting at er and moving to golgi, they associate with cholesterol and lipoproteins to form chylomicrons which move out of epithelial cells by exocytosis and into lacteals (at centre of each villus) then into blood
triglycerides in them are hydrolysed by enzyme in endothelial cells of blood caps- then diffuse into cells

Question 40

how are amino acids absorbed?

Answer 40

via co-transport

Question 41

what is an atheroma?
what is chd?

Answer 41

when damage occurs to endothelium of artery, wbc and lipids clump together to form fatty streaks which build up and form plaques called atheromas. this partially blocks lumen of artery so restricts blood flow increasing bp
chd is a type of cardiovascular disease occuring when theres lots of atheromas. can lead to myocardial infarction

Question 42

what is an aneurysm?

Answer 42

atheromas damage and weaken and narrow arteries increasing bp
blood flows through at high bp it may push inner layers of artery through the outer elastic layer causing it to swell
the aneurysm can burst causing a haemorrhage

Question 43

what is thrombosis?

Answer 43

atheroma can rupture endothelium and damage wall leaving rough surface
platelets and fibrin accumulate at damaged site and form clot which blocks artery or can dislodge and block blood vessel elsewhere
debris from rupture can also cause another blood clot further down

Question 44

what is myocardial infarction?

Answer 44

coronary artery becomes blocked so area of heart cut off from blood supply so receives no o2 and cant respire- causes myocardial infarction (heart attack) which can damage heart muscle. large area infected can be fatal as causes heart failure
chest pain, short of breath, sweating

Question 45

risk factors of cvd

Answer 45

high blood cholesterol- main constituent of atheromas so can raise bp and cause clots and myocardial infarction
saturated fat- increase cholesterol
salt- increase bp
smoking- nicotine raises bp, co reduces transport of o2 so can cause heart attack, decreases antioxidants in blood so cell damage in artery wall more likely
high bp- can damage walls, increased risk of atheromas which leads to clots
anything raising bp (weight, no exercise, alcohol) ,age, being male

Question 46

what is the mass transport system in plants?

Answer 46

xylem tissue- transports water and mineral ions from roots to leaves
phloem tissue- transports organic substances up and down the plant

Question 47

what are xylem vessels?

Answer 47

part of the xylem tissue that actually transports the water and ions. long, tube like structures formed from dead cells. no end walls so uninterrupted tube

Question 48

what is the cohesion-tension theory of water transport?

Answer 48

cohesion and tension help water move against gravity
. water evaporates from leaves
. this creates tension which pulls more water into leaf
. water molecules are cohesive so when some are pulled up, others follow so whole column of water moves
. water enters stem through roots

Question 49

what is transpiration?

Answer 49

evaporation of water from plants surface
.water evaporates from moist cell walls and accumulates in spaces between cells in leaf
. stomata open and it moves out of leaf down conc grad

Question 50

what factors affect transpiration?

Answer 50

light- stomata open in light so CO2 enters so rate increases
temp- warm temp means water mols have more energy so evaporate faster so higher conc grad
humidity- less humid means higher conc grad
wind- air movement blows water away from stomata so increases conc grad

Question 51

what is a potometer?
how do you use it?

Answer 51

apparatus that measures transpiration rates (uptake of water)
1) cut shoot underwater to prevent air getting to it
2)assemble potometer underwater and insert shoot underwater
3) remove from water but keep end of capillary tube submerges
4) dry leaves and allow time for shoot to acclimatise then shut tap
5) remove end of cap tube from water until 1 bubble forms then put back
6)record start position of bubble and start stopwatch and record distance moved per unit time
7)rate of air bubble movement= rate of transpiration

Question 52

structure of phylem

Answer 52

sieve tube elements (living cells that form tube) and companion cells (one for each sieve tube element, they carry out living functions for them)

Question 53

what is translocation?

Answer 53

movement of solutes (assimilates) to where theyre needed in plant
energy requiring process
moves solutes from sources (where its made) to sinks (where its used up) down conc grad
enzymes maintain this conc grad by changing solutes at sink (breaking down or making)

Question 54

what is the mass flow hypothesis?

Answer 54

suggests how transport in phloem happens
1) - active transport loads solutes from companion cells to sieve tubes at source
- this lowers water pot in sieve tubes so water enters by osmosis from xylem to companion cells
- this creates high press in sieve tubes at source end of phloem
2) - at sink end, solutes are removed from phloem to be used up
- this increases water pot inside sieve tubes by osmosis
- this lowers pressure in sieve tubes
3) - the result is a pressure grad from source to sink
- this grad pushes solutes along sieve to sink
- when they reach the sink, solutes are used or stored

Question 55

evidence for mass flow

Answer 55

• if ring of bark (contains phloem not xylem) is removed, a bulge forms. fluid in bulge has higher conc of sugars than fluid below ring- evidence for downward flow of sugars
• radioactive tracer can track movement of organic substances
• pressure in phloem can be investigated using aphids (pierce phloem then bodies removed leaving mouthpart behind so sap flows out). sap flows quicker nearer leaves- evidence for pressure grad
• metabolic inhibitor (stops ATP production) put in phloem, translocation stops- evidence active transport involved

Question 56

objections to mass flow

Answer 56

• sugar travels to many sinks not just one with highest water pot as model suggests
• sieve plates would create barrier to mass flow- lots of pressure needed to get solutes through at reasonable rate

Question 57

how can translocation be modelled using radioactive tracers?

Answer 57

supply part of plant w organic substance with radioactive label eg radioactive CO2
this becomes incorporated into organic substances produced by leaf which will be moved around by translocation
movement tracked by autoradiography
plant is killed and then placed on photographic film to reveal where tracer has spread to (radioactive substance is present wherever film turns black)