mass transport (exchange Flashcards
what is the structure of haemoglobin
quaternary structure protein with 4 polypeptide chains , 2 alpha , 2 beta with each polypeptide chain associated with a haem group and a iron ion
how many oxygens can bind to one iron ion
1 oxygen molecule binds to one iron ion . therefore 4 o2 molecules can be carried by a single haemoglobin
what is the primary structure of haemoglobin
sequence of amino acids in the four polypeptide chains
what is the secondary structure of haemoglobin
each of these polypeptide chains is coiled into a helix
what is the tertiary structure of haemoglobin
each polypeptide chain is folded into a precise shape - an important factor in its ability to carry oxygen
what is the quaternary structure of haemoglobin
all 4 polypeptide chains are linked together to form an almost spherical molecule
when does haemoglobin dissociate and accociate with oxygen
haemoglobin associates with oxygen in the lungs and it dissociates in the tissues
what is the role of haemoglobin
to transport oxygen .
readily associate with oxygen at the surface where gas exchange takes place
readily dissociate from oxygen at those tissues requiring it
what is partial pressure of oxygen
p02 is a measure of oxygen concentration of dissoloved oxygen in cells
where is there a high p02
oxygen loads
where is there a low p02
oxygen unloads
will there be a high or low concentration of co2 in alveoli
low concentration
will there be a high or low concentration of co2 in the respiring tissue
high concentration
how does haeomoglobin change its affinity for oxygen
haemoglobin changes its affinity for oxygen under different conditions . it acheives this because its shape changes in the prescence of certain substances eg carbon dioxide
describe the quaternary structure of haemoglobin
four polypeptide chains joined 2 beta and 2 alpha . which link to form a spherical molecle each one with a haem group and fe2+ ion , meaning 4 o2 molecules can join to one haemoglobin
in the oxygen dissociation curve why is the partial pressure of oxygen low at the start
At the start there is a low po2 , haemoglobin had a high affinity for oxygen so there’s a low saturation , the shape of haemoglobin makes it difficult for the first oxygen molecule to bind , because the polypeptide subunits are closely United . This is in the respiring tissues ,
First oxygen binding causes a change in the quaternary structure which makes it easier for the other subunits to bind to an oxygen molecule . .
The curve shows positive cooperativista as it takes a smaller increase in the partial pressure of oxygen to bind to the second
Lastly it is difficult for o2 to load so slows down the rate , this is because high po2 , haemoglobin had a high affinity for o2 so there’s s high saturation . More binding sites occupied so gradient reduces and curve flattens off
What is partial pressure measured in
Kilopascals
What happens to the curve when co2 is higher
Shifts right
What happens when co2 is lower
Shifts left
Why does it shift right in prescence of co2
Ph decreases , tertiary structure changes and it unloads more . Never fully saturated , affinity for o2 is lower .
Why does it shift left with lower co2
Ph raised , less co2 , saturation of haemoglobin is higher , affinity is higher , it is loading more
What’s the shift called
The Bohr shift
What happens to the curve for the lugworm ( low o2 environment )
Shifts to the left , higher affinity for oxygen so has to load more and at a low partial prsssure of oxygen oxygen binds to haemoglobin very quickly . Another way is that it’s respiring less so less co2 is produced and needs to load more
What effect do hawks have on the curve ( they have a high respiratory rate)
More respiration , unloads at low partial pressures of oxygen there’s is a lot of co2 produced so shifts to the right
Mice curve
Shifts to the right as they have a high respiration rate and need to unload more oxygen for this
Describe and explain why the curves are different for the elephant and shrew ( shrew to the right of elephant
The curve for the elephant is shifted to the left , this is because it has a low metabolic rate and therefore a higher affinity for oxygen as it needs to load more oxygen than shrews . Additionally it has a lower surface area to volume ratio than the shrew therefore lower metabolic rate . Whereas the curve for the shrew is shifted to the right because it has a faster metabolic rate therefore a lower affinity for oxygen as it needs to unload more oxygen to the respiring tissues
Describe and explain the shape of the oxygen dissociation curve for humans
The curve at the start has a low partial pressure of oxygen and a low saturation of haemoglobin and this makes it more difficult for the first oxygen because of haemoglobins shape . As polypeptide chains are tightly bound . As partial pressure increases haemoglobin changes shape making it easier for oxygen to bind however as partial pressure gets higher the graph levels off has the difficulty to bind is increased as more harm groups are occupied and therefore a high saturation of oxygen
what does the superior vena cava do
brings deoxygenated blood from head to right atrium from head
what does the inferior vena cava do
brings deoxygenated blood from lower parts of the body to the right atrium
what does the right ventricle do
pumps the blood through the pulmonary artery to the lungs
what does the pulmonary vein do
oxygenated blood is brought from the lungs and to the left atrium
what does the left ventricle do
pump blood through the aorta to the head and body cells
whats the septum
the septum prevents any blood from passing directly through
what is the right atrioventricular valve called
tricuspid valve
what is the left atrioventricular valve called
bicuspid valve
what do the valves do
prevent the backflow of blood into the atria when ventricles contract
what are some features of the atrium
its thin walled , elastic an stretches as it collects blood
why does the ventricle have a much thicker wall
thicker mucsular wall as it has to contract strongly to pump blood some distance , either to lungs or rest of body
what do the tendons attacthed to the atrioventricular valves do
ensure that the valves open in the right direction
whats the coronary artery
branches of aorta and supplies heart muscle with oxygen and nutrients
what is the cirulatory system of mammals
closed , double circulatory system
how many times does blood pass through the heart
twice
what happens when blood is passed through the lungs
its pressure is reduced , therefore if it was then passed to body cirulation would be very slow , the heart increases pressure and as a result substances are delivered to the rest of the body quickly, this is necessary as mammals have a high body temperature and hence a high rate of metabolism
What’s the first step in the cardiac cycle
Diastole , blood flowing into heart through vena cava and pulmonary vein , relaxation of atrium to let blood into ventricles , atrioventricular valves slightly open , semilunar valves closed ,atrial diastole and ventricular diastole . Ventricles recoil and reduce pressure
Whats the next step in the cardiac cycle
When pressure in atria is higher than in ventricles , atrioventricular valves open and atrium contract which forces blood into the ventricles . This is called atrial systole and ventricular diastole to let blood in . Semilunar valves shut
What is the third step in the cardiac cycle
Once pressure in ventricles rises , blood flows into aorta and pulmonary artery . Ventricular systole (walls contract ) and atrial diastole , semilunar valves open and atrioventricular valves shut (to prevent back flow of blood into atria because pressure in atria is also lower than ventricles )
How do you calculate cardiac output
Stroke volume x heart rate
What is cardiac output
Volume of blood from 1 ventricle in 1 minute
What is heart rate
Rate at which the heart beats
What is stroke volume
Volume of blood pumped out at each beat
What’s cardiac output units
Dm3 min-1 or cm3min-1
What’s contraction
Systole
What’s relaxation
Diastole
What happens to pressure during systole
Pressure increases
What is the cardiac cycle
Sequence of events that is repeated in humans around 70 times each minute when at rest
What happens to the pressure in the atrium during the cardiac cycle
Pressure increases when they start to contact , then pressure decreases as blood flows into ventricles , then the pressure increases again as they refill with blood . Then pressure decreases as some blood leaks and starts to flow into ventricles . The pressure in the atria is usually relatively low as thin walls cannot create much force
What happens to the prsssure in the ventricles
Increase in pressure when they start to fill , massive increase in pressure when they contact , decrease as they empty , slight increase when they refill again
What happens to the pressure in the aorta
Low pressure at the start then pressure increases when ventricles contract , pressure decreases as blood moves through
What do the atrioventricular valves do
Prevent back flow of blood when ventricles contract into atria making sure blood is forced into the aorta and pulmonary artery
What do semilunar valves do
Prevent back flow of blood into ventricles when pressure is lower in ventricles
What are pocket valves
Valves in veins which ensure when veins are squeezed blood flows to the heart and not away from it
What are valves made of
A number of flaps of tough , flexible , fibrous tissue
What are the different types of blood vessels and their functions
Arteries - carry blood away from the heart and into aterioles
Arterioles- smaller arteries that control blood flow from arteries to capillaries
Capillaries - tiny vessels that link aterioles to veins
Veins - carry blood from capillaries back to the heart
Describe the structure of an artery
-They have a thick muscle layer which is thicker than veins so that constriction and dilation can occur to control the volume of blood
-they have a thick elastic layer which is thicker than in veins to help maintain high blood pressure , the walls can stretch and recoil in response to the heart beat
-they have a thick wall , thicker than in veins to help prevent the vessels bursting due to high pressure
-they have a smaller lumen than veins as thicker walls
-they have no valves as blood tends to flow in correct direction due to high pressure
-artery walls are thick and muscular and have elastic tissue to stretch and recoil as the heart beats which helps maintain high pressure
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What are the layers of the artery
They have a lumen which is the central cavity of blood vessel through which blood flows , an inner lining which is smooth to reduce friction and thin to allow diffusion , an elastic layer , muscle layer and tough outer layer
All arteries carry oxygenated blood except pulmonary artery
Describe the structure of veins
-They have a thin elastic layer , as pressure is lower than arteries so won’t burst
-thin muscle layer , compared to arteries so cannot control blood flow
Overall thickness of wall is thin , as low pressure within veins so no risk of bursting , it also allows them to be flattened easily , aiding the flow of blood within them
-they have valves , throughout to ensure that blood does not flow backwards , which might happen as pressure is low
-when body muscles contract veins are compressed , pressurising the blood within them , the valves ensure that the pressure directs the blood in one direction only , towards the heart
Describe the structure and function of aterioles
They carry blood under low pressure , they control the flow of blood between arteries and capillaries
They have a thicker muscle layer than arteries which allows constriction of lumen , this constricts the flow of blood and so controls it’s movement into the capillaries that supply the tissues with blood
They have a thinner elastic layer because blood pressure is lower
What’s the structure and function of capillaries
Capillaries form capillary beds as exchange surfaces , which are many branched capillaries
They are one cell thick and red blood cells can only just fit through as they have a narrow diameter to slow blood flow
This means the red blood cells are squashed against the walls , maximising diffusion
They have no muscle layer
No elastic layer
One cell thick lining layer ,which allows rapid diffusion of materials between the blood and the cells
No valves
Narrow lumen
What is tissue fluid
Fluid containing glucose , amino acids , fatty acids , ions and oxygen in solution
What is tissue fluid able to do
Able to receive co2 and other waste materials from the tissues
What is tissue fluid formed from
Blood plasma
How is tissue fluid formed
Hydrostatic pressure is high in the anteriores side of capillaries which causes ultrafiltration so small molecules are forced out of the capillaries eg water , glucose , oxygen and go to tissues
and high water potential so water leaves my osmosis
what molecules dont leave the capillaries
red blood cells , platelets and large proteins as they are too large
how is tissue fluid then re absorbed
water potential is now lower in the capillaries than the tissues so water moves in by osmosis at the venule end . we have a low hydrostatic pressure as loss of tissue fluid reduces hydrostatic pressure , so water moves back in . additionally as cells are respiring they are producing co2 and urea which moves into the capillaries by diffusion .
what happens to the excess water in the tissues and why
once equilibrium is reached no more water will move into the capillaries . therefore the rest of the liquid is absorbed into the lymphatic system which surround blood vessles and eventually bring it into the blood
how does fluid move through the lymphatic vessels
contraction of body mucscles squezes and moves the fluid towards the direction of the heart
what feature of water causes cohesion
water being dipolar and therefore has hydrogen bonds which sticks molecules together. this keeps the transpiration stream going
why is adhesion a benefit of transpiration
can form hydrogen bonds with other molecules eg the wall of the xylem
how is water transported up the xylem . explain in terms of water poteintial and pressure
- water potential at the stomata is higher than in the atmosphere and therefore water diffuses out of leaves by osmosis . called evaportation
- theres a water potential gradient between cells and leaf as water potential is higher in the xylem so moves into cells
-water is pulled up in the xylem which is called negative pressure . cohesion of water molecules pull them up by hydrogen bonds creating a constant transpiration stream
-as water moves into the roots pressure increases and takes water up . gradient between soil and root hair cells , higher in soil than cells so water moves in by osmosis
what are the features of the xylem
- strengthened by lignin and has no internal cell walls , and made of dead cells
how do we measure rate of transpiration
with a potometer
how does a potometer work
-record distance of air bubble at start and end , to calculate rate.
- use different factors which will effect transpiration
why do we have a reservoir at the middle and a tap on the potometer
- moves bubble to the right , back to the start of the zero end so you can do repeats
why must the shoot be cut under water
so you dont break the transpiration stream with air getting into the xylem
Why do the leaves need to be dry at the start of the potometer experiment
You want to start with a concentration gradient , and you don’t want the water potential on the outside to effect the results
What are the different environmental factors we can investigate
-humidity
-temperature
-wind intensity
-light intensity
how do you calculate the rate of water uptake in a potometer
pi x r2 x l
r =radius of capillary tube
l= distance bubble moved
what are the units for water uptake
mm3min-1
what happens to a tree trunk diameter at night and day
at night the diameter of a tree trunk increases whereas in the day it is smaller. this is because of adhesion .in the day transpiration occurs and therefore the walls of the xylem are pulled in whereas at night theres less adhesion because photosynthesis is not occuring
a student used the appartus shown and a digital balance to determine the rate of water movement in a celery stalk in grams per hour per group of xylem vessels. the student measured the time taken for the water movement .
give two other measurements he made to calculate the rate of water movement
-the initial and final mass
-the amount of xylem vessels
give the reason for adding a layer of oil to the water in the beaker
to prevent evapouration
how is the phloem adadpted
sieve tube element , with sieve plates which have pores. they reduce the amount of organelles they have by having a companion cell with all the organelles needed
eg translocation requires ATP and this is provided by mitocondria in the companion cells.
what is the source
-where the organic substance is created eg sucrose in a leaf cell as photosynthesis occurs
what is the sink
where the organic substance is transported eg sucrose in respiring cells
what is mass transport of organic substances in the phloem called
translocation
what happens first between the source cells and phloem
sucrose in source cell is transported into the companion cell by facilitated diffusion. then h+ ions in the phloem are actively transported into the companion cell and then with sucrose transported out again
what is the mass flow hypothesis
1) source cell creates sucrose which lowers water potential so water enters by osmosis
2) at sink cell its respiring so using sugars and therefore has more positibe water potential and water leaves by osmosis
3)source cell has an increase in hydrostatic pressure as water moves in whereas sink cell has decreased hydrostatic pressure as water and liquid moves out
4) therefore solution is forced towards sink cell via the phloem
describe translocation
1) after co transport of H+ with sucrose , water moves by osmosis into phloem as low water potential in the phloem(xylem has higher water potential)
2) high hydrostatic in phloem due to sucrose and water and so sucrose moves by facilitated diffusion at first and then active transport once equilibrium reached, into the sink cell
3) lower hydrostatic pressure at the bottom and higher water potential as sucrose conc lowered near sink cell therefore water moves back into xylem and water potential is higher in phloem
why can we not just use facilitated difusion to get all sucrose into phloem
because conc of sucrose is building up in phloem and so we have a higher conc inside phloem so need to use active transport
explain why some insects can take up sap from the phloem without using their jaw muscles
there is a high hydrostatic pressure in the phloem as high conc of water which enters b osmosis and sugars and this means the high pressure pushes the organic substances out into the insects mouth
some insects polymerise these sugars into polysaccharies suggest the advantage of this
polysacchardies are insoluble therefore do not affect water potential
what are the 3 experiments for evidence for mass flow
-using radioisotopes(tracer experiments)
-ringing experiment
-aphids
describe the tracer experiment
- radioactive carbon is used for a photosynthesising plant
-we can take a thin cross section of stem and place on x ray film - we will find that the phloem contains radiation
-this shows that the product of photosynthesis are being transported in the phloem
describe the ringing experiment
-remove ring of bark , bark contains the phloem and xylem left in tact
-fluid accumulates in the phloem on source side of ring which causes swelling
-tissues below the ring will die as cannot get organic substances required for respiration
-this shows transport of organic substances is via the phloem and not the xylem
how does the ringing experiment show that transport of organic substances is via the phloem and not xylem
if the xylem transported organic substances you would have expected fluid to not accumulate and tissues below ring will not die as xylem is stilll intact
describe the aphid experiment
-aphids feed by inserting their stylet into the phloem and then body of aphid is removed . sap leakes out of the mouthpart
-this shows the phloem is under positive pressure and transports organic substances as sap contains organic substances
what is evidence for mass flow
-pressure within sieve tubes as shown by sap being released when they are cut
-the concentration of sucrose is higher in leaves than roots
-downward flow in phloem occurs in daylight but ceases when leaves are shaded
-increases in sucrose levels are followed by similar increases in phloem a little later
-metabolic poisons /lack of oxygen inhibit translocation of sucrose in phloem (as lack of respiration in sink)
-companion cells posess many mitocondria and readily produce ATP)
what is mass flow
mass flow involves the generation of high hydrostatic pressure at the source by loading sucrose into the phloem
what is the evidence against mass flow
-not all solutes move at the same speed - should do if by mass flow
-function of sieve plates is unclear
- sucrose is delivered at more or less the same rate at all regions rather than faster where there is the lowest conc of sucrose which mass theory would suggest
how do you calculate heart rate from a table of times and volume of blood in ventricle
find how many seconds it takes to get back to the same value and then this time is 1 heart beat . divide 60 by this value
how do you calculate stroke volume from these results
stroke volume is the volume of blood pumped out of the left ventricle during one cardiac cycle. so find the highest value and lowest value and minus them
some people produce a much higher ventricular blood pressure than normal. this can cause tissue fluid to build up outside the blood capillaries of these people . explain why
more fluid is forced out of capillary due to high pressure and therefore less return of fluid to capillary due to already high pressure . additionally lymphatic system cannot drain away all excess fluid
how does elastic tissue help to smooth out the flow of blood in the blood vessel
the elastic tissue can expand to accomodate increase in blood volume as blood volume increases when ventricle contracts. and the elastic tissue recoils when blood volume decreases as veltricle relaxes
explain the role of the heart in the formation of tissue fluid
contraction of ventricles produces high hydrostatic pressure. this forces water and some dissolved substances out of blood capillaries
suggest how a blockage in the lymphatic system could cause lymphodema
excess tissue fluid cannot be reabsorbed and therefore builds up
What effect does carbon dioxide have on PH have on the blood
With increasing carbon dioxide concentration , the PH of the blood decreases as acidity increases
What are some adaptations of the capillaries
Capillary wall is one cell thick , therefore provides a short diffusion distance for faster diffusion
Capillary has a narrow lumen which reduces flow rate giving more time for diffusion
Permeable wall
What are some adaptations of the capillaries
Capillary wall is one cell thick , therefore provides a short diffusion distance for faster diffusion
Capillary has a narrow lumen which reduces flow rate giving more time for diffusion
Permeable wall
describe mass flow
- sucrose actively transported into phloem by companion cells]
- or sucrose is co transported into phloem
this lowers the water potential of the phloem and water enters the phloem by osmosis from the xylem
-this produces higher hydrostatic pressure
-mass flow to respiring cells
-unloaded from phloem by active transport
what is the structure of the aorta wall
-smooth muscle in the aorta wall withstands the high blood pressure.
-elastic tissue smooths and maintains blood pressure
-( stretches during systole-blood pumped out and relaxes during diastole )
-smooth endothelium helps reduce friction
-collagen prevents wall splitting
