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Biology Alevel > mass transport (exchange > Flashcards

mass transport (exchange Flashcards

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1
Q

what is the structure of haemoglobin

A

quaternary structure protein with 4 polypeptide chains , 2 alpha , 2 beta with each polypeptide chain associated with a haem group and a iron ion

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2
Q

how many oxygens can bind to one iron ion

A

1 oxygen molecule binds to one iron ion . therefore 4 o2 molecules can be carried by a single haemoglobin

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3
Q

what is the primary structure of haemoglobin

A

sequence of amino acids in the four polypeptide chains

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4
Q

what is the secondary structure of haemoglobin

A

each of these polypeptide chains is coiled into a helix

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5
Q

what is the tertiary structure of haemoglobin

A

each polypeptide chain is folded into a precise shape - an important factor in its ability to carry oxygen

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6
Q

what is the quaternary structure of haemoglobin

A

all 4 polypeptide chains are linked together to form an almost spherical molecule

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7
Q

when does haemoglobin dissociate and accociate with oxygen

A

haemoglobin associates with oxygen in the lungs and it dissociates in the tissues

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8
Q

what is the role of haemoglobin

A

to transport oxygen .
readily associate with oxygen at the surface where gas exchange takes place
readily dissociate from oxygen at those tissues requiring it

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9
Q

what is partial pressure of oxygen

A

p02 is a measure of oxygen concentration of dissoloved oxygen in cells

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10
Q

where is there a high p02

A

oxygen loads

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11
Q

where is there a low p02

A

oxygen unloads

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12
Q

will there be a high or low concentration of co2 in alveoli

A

low concentration

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13
Q

will there be a high or low concentration of co2 in the respiring tissue

A

high concentration

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14
Q

how does haeomoglobin change its affinity for oxygen

A

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

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15
Q

describe the quaternary structure of haemoglobin

A

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

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16
Q

in the oxygen dissociation curve why is the partial pressure of oxygen low at the start

A

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

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17
Q

What is partial pressure measured in

A

Kilopascals

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18
Q

What happens to the curve when co2 is higher

A

Shifts right

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19
Q

What happens when co2 is lower

A

Shifts left

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20
Q

Why does it shift right in prescence of co2

A

Ph decreases , tertiary structure changes and it unloads more . Never fully saturated , affinity for o2 is lower .

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21
Q

Why does it shift left with lower co2

A

Ph raised , less co2 , saturation of haemoglobin is higher , affinity is higher , it is loading more

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22
Q

What’s the shift called

A

The Bohr shift

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23
Q

What happens to the curve for the lugworm ( low o2 environment )

A

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

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24
Q

What effect do hawks have on the curve ( they have a high respiratory rate)

A

More respiration , unloads at low partial pressures of oxygen there’s is a lot of co2 produced so shifts to the right

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25
Q

Mice curve

A

Shifts to the right as they have a high respiration rate and need to unload more oxygen for this

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26
Q

Describe and explain why the curves are different for the elephant and shrew ( shrew to the right of elephant

A

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

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27
Q

Describe and explain the shape of the oxygen dissociation curve for humans

A

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

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28
Q

what does the superior vena cava do

A

brings deoxygenated blood from head to right atrium from head

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29
Q

what does the inferior vena cava do

A

brings deoxygenated blood from lower parts of the body to the right atrium

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30
Q

what does the right ventricle do

A

pumps the blood through the pulmonary artery to the lungs

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31
Q

what does the pulmonary vein do

A

oxygenated blood is brought from the lungs and to the left atrium

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32
Q

what does the left ventricle do

A

pump blood through the aorta to the head and body cells

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33
Q

whats the septum

A

the septum prevents any blood from passing directly through

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34
Q

what is the right atrioventricular valve called

A

tricuspid valve

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35
Q

what is the left atrioventricular valve called

A

bicuspid valve

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36
Q

what do the valves do

A

prevent the backflow of blood into the atria when ventricles contract

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37
Q

what are some features of the atrium

A

its thin walled , elastic an stretches as it collects blood

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38
Q

why does the ventricle have a much thicker wall

A

thicker mucsular wall as it has to contract strongly to pump blood some distance , either to lungs or rest of body

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39
Q

what do the tendons attacthed to the atrioventricular valves do

A

ensure that the valves open in the right direction

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40
Q

whats the coronary artery

A

branches of aorta and supplies heart muscle with oxygen and nutrients

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41
Q

what is the cirulatory system of mammals

A

closed , double circulatory system

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42
Q

how many times does blood pass through the heart

A

twice

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43
Q

what happens when blood is passed through the lungs

A

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

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44
Q

What’s the first step in the cardiac cycle

A

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

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45
Q

Whats the next step in the cardiac cycle

A

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

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46
Q

What is the third step in the cardiac cycle

A

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 )

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47
Q

How do you calculate cardiac output

A

Stroke volume x heart rate

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48
Q

What is cardiac output

A

Volume of blood from 1 ventricle in 1 minute

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49
Q

What is heart rate

A

Rate at which the heart beats

50
Q

What is stroke volume

A

Volume of blood pumped out at each beat

51
Q

What’s cardiac output units

A

Dm3 min-1 or cm3min-1

52
Q

What’s contraction

A

Systole

53
Q

What’s relaxation

A

Diastole

54
Q

What happens to pressure during systole

A

Pressure increases

55
Q

What is the cardiac cycle

A

Sequence of events that is repeated in humans around 70 times each minute when at rest

56
Q

What happens to the pressure in the atrium during the cardiac cycle

A

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

57
Q

What happens to the prsssure in the ventricles

A

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

58
Q

What happens to the pressure in the aorta

A

Low pressure at the start then pressure increases when ventricles contract , pressure decreases as blood moves through

59
Q

What do the atrioventricular valves do

A

Prevent back flow of blood when ventricles contract into atria making sure blood is forced into the aorta and pulmonary artery

60
Q

What do semilunar valves do

A

Prevent back flow of blood into ventricles when pressure is lower in ventricles

61
Q

What are pocket valves

A

Valves in veins which ensure when veins are squeezed blood flows to the heart and not away from it

62
Q

What are valves made of

A

A number of flaps of tough , flexible , fibrous tissue

63
Q

What are the different types of blood vessels and their functions

A

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

64
Q

Describe the structure of an artery

A

-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
-

65
Q

What are the layers of the artery

A

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

66
Q

All arteries carry oxygenated blood except pulmonary artery

A
67
Q

Describe the structure of veins

A

-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

68
Q

Describe the structure and function of aterioles

A

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

69
Q

What’s the structure and function of capillaries

A

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

70
Q

What is tissue fluid

A

Fluid containing glucose , amino acids , fatty acids , ions and oxygen in solution

71
Q

What is tissue fluid able to do

A

Able to receive co2 and other waste materials from the tissues

72
Q

What is tissue fluid formed from

A

Blood plasma

73
Q

How is tissue fluid formed

A

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

74
Q

what molecules dont leave the capillaries

A

red blood cells , platelets and large proteins as they are too large

75
Q

how is tissue fluid then re absorbed

A

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 .

76
Q

what happens to the excess water in the tissues and why

A

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

77
Q

how does fluid move through the lymphatic vessels

A

contraction of body mucscles squezes and moves the fluid towards the direction of the heart

78
Q

what feature of water causes cohesion

A

water being dipolar and therefore has hydrogen bonds which sticks molecules together. this keeps the transpiration stream going

79
Q

why is adhesion a benefit of transpiration

A

can form hydrogen bonds with other molecules eg the wall of the xylem

80
Q

how is water transported up the xylem . explain in terms of water poteintial and pressure

A
  • 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
81
Q

what are the features of the xylem

A
  • strengthened by lignin and has no internal cell walls , and made of dead cells
82
Q

how do we measure rate of transpiration

A

with a potometer

83
Q

how does a potometer work

A

-record distance of air bubble at start and end , to calculate rate.
- use different factors which will effect transpiration

84
Q

why do we have a reservoir at the middle and a tap on the potometer

A
  • moves bubble to the right , back to the start of the zero end so you can do repeats
85
Q

why must the shoot be cut under water

A

so you dont break the transpiration stream with air getting into the xylem

86
Q

Why do the leaves need to be dry at the start of the potometer experiment

A

You want to start with a concentration gradient , and you don’t want the water potential on the outside to effect the results

87
Q

What are the different environmental factors we can investigate

A

-humidity
-temperature
-wind intensity
-light intensity

88
Q

how do you calculate the rate of water uptake in a potometer

A

pi x r2 x l
r =radius of capillary tube
l= distance bubble moved

89
Q

what are the units for water uptake

A

mm3min-1

90
Q

what happens to a tree trunk diameter at night and day

A

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

91
Q

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

A

-the initial and final mass
-the amount of xylem vessels

92
Q

give the reason for adding a layer of oil to the water in the beaker

A

to prevent evapouration

93
Q

how is the phloem adadpted

A

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.

94
Q

what is the source

A

-where the organic substance is created eg sucrose in a leaf cell as photosynthesis occurs

95
Q

what is the sink

A

where the organic substance is transported eg sucrose in respiring cells

96
Q

what is mass transport of organic substances in the phloem called

A

translocation

97
Q

what happens first between the source cells and phloem

A

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

98
Q

what is the mass flow hypothesis

A

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

99
Q

describe translocation

A

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

100
Q

why can we not just use facilitated difusion to get all sucrose into phloem

A

because conc of sucrose is building up in phloem and so we have a higher conc inside phloem so need to use active transport

101
Q

explain why some insects can take up sap from the phloem without using their jaw muscles

A

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

102
Q

some insects polymerise these sugars into polysaccharies suggest the advantage of this

A

polysacchardies are insoluble therefore do not affect water potential

103
Q

what are the 3 experiments for evidence for mass flow

A

-using radioisotopes(tracer experiments)
-ringing experiment
-aphids

104
Q

describe the tracer experiment

A
  • 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
105
Q

describe the ringing experiment

A

-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

106
Q

how does the ringing experiment show that transport of organic substances is via the phloem and not xylem

A

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

107
Q

describe the aphid experiment

A

-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

108
Q

what is evidence for mass flow

A

-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)

109
Q

what is mass flow

A

mass flow involves the generation of high hydrostatic pressure at the source by loading sucrose into the phloem

110
Q

what is the evidence against mass flow

A

-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

111
Q

how do you calculate heart rate from a table of times and volume of blood in ventricle

A

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

112
Q

how do you calculate stroke volume from these results

A

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

113
Q

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

A

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

114
Q

how does elastic tissue help to smooth out the flow of blood in the blood vessel

A

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

115
Q

explain the role of the heart in the formation of tissue fluid

A

contraction of ventricles produces high hydrostatic pressure. this forces water and some dissolved substances out of blood capillaries

116
Q

suggest how a blockage in the lymphatic system could cause lymphodema

A

excess tissue fluid cannot be reabsorbed and therefore builds up

117
Q
A
118
Q

What effect does carbon dioxide have on PH have on the blood

A

With increasing carbon dioxide concentration , the PH of the blood decreases as acidity increases

119
Q

What are some adaptations of the capillaries

A

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

120
Q

What are some adaptations of the capillaries

A

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

Biology Alevel (18 decks)

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