Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

a level biology > 3.3.4 Mass Transport > Flashcards

3.3.4 Mass Transport Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is meant by mass transport?

A

The bulk movement of materials from exchange surfaces to the cells throughout the organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Fick’s law?

A

concentration gradient x surface area
————————————————
diffusion pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does whether an organism need a mass transport system rely on?

A

how active the organism is (waste produced, material required), how far away is the external environment, calculated using Fick’s law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

when would a mass transport system be faster than diffusion?

A

when the majority of cells are too far away from exchange surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do efficient systems have to maximise diffusion?

A

A suitable transport medium (usually liquid but can be gas, materials such as oxygen and waste dissolve), a closed system of tubular vessels (contains/holds medium, branching to all parts, medium is close to cells), mechanisms for movement of tissue fluid (generates pressure, enables medium to move)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the medium in the circulatory system?

A

Blood containing haemoglobin to carry oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the closed system of tubular vessels in the circulatory system?

A

Veins, arteries and capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the mechanism for movement in the circulatory system?

A

The heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the four chambers of the heart?

A

Left ventricle, right ventricle, right atrium, left atrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the vessels coming to and from the heart?

A

Pulmonary artery, pulmonary vein, aorta, vena cava

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the function of valves?

A

to prevent the back flow of blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where is the SAN node located?

A

The top of the right atrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What type of muscle is the heart?

A

A cardiac muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What system is the heart part of?

A

The circulatory system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is meant by myogenic?

A

The heart naturally contracts and relaxes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is meant by a double circulatory system?

A

Blood passes through the heart twice, through two different circuits, circuit one links the heart to the rest of the body, circuit two links the heart to the lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe the journey of a red blood cell, naming the main blood vessels and chambers of the heart.

A

Deoxygenated red blood cells enter the right atrium via the vena cava, it then moves through an atrioventricular valve into the right ventricle and pushed through a semi lunar valve into the pulmonary artery and towards the lungs. At the lungs oxygen diffuses into the blood and carbon dioxide diffuses out. Oxygenated blood then re-enters the heart through the pulmonary veins into the left atrium, it then moves through the left atrioventricular valve into the left atrium and through the left semi lunar valve into the aorta where it is transported around the body for oxygen diffuses into the working muscles. The cycle then starts again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how does the wall thickness in the heart maximise mass transport?

A

The left ventricle is much thicker as it is more muscular for a more forceful contraction as it requires more pressure to pump oxygenated blood around the body to the respiring cells and then back to the heart. Right ventricle not as thick as blood only travels to the lungs so requires lower pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do the valves in the heart maximise mass transport?

A

They open and close between the atrium and ventricle and ventricle and vessels, they prevent the back flow of blood, to move the blood in one direction and only open when the chamber is filled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which valves are between the atrium and ventricle?

A

Right atrioventricular (bicuspid valve) and left atrioventricular (tricuspid valve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which valves are between the ventricles and vessels?

A

Semi-lunar valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How to the valves close?

A

Pressure is higher below the valve where concave, ventricle fills with blood, pushes the flexible, fibrous tissue together, tissue form a tight fit/no gap, causes the ‘lub dub’ sound, prevents blood from moving backwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do the valves open?

A

Pressure is higher above the valve, atrium fills with blood, ventricle empties, pushes the flexible, fibrous tissue apart, tissue form a gap, so blood can flow through

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is valve disease?

A

Leaky valve, can’t prevent the back flow , forms clots, doesn’t get enough oxygen as less pressure, lack energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the treatments for valve disease?

A

Mechanical valves, animal valves (pigs or cows)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are the advantages of using animal valves to treat valve disease?

A

Cows are in large supply, fairly well tested, fewer long term issue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the disadvantages of using animal valves to treat valve disease?

A

Unethical to use cows, not suitable for all, some feelings, can need replaced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How many times does the heart contact each minute at rest?

A

Around 70 times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is meant by diastole?

A

Relaxation of the heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is meant by systole?

A

Contraction of the heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is haemoglobin?

A

A quaternary structure protein, a respiratory pigment, transports oxygen in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the quaternary structure of haemoglobin?

A

2 beta and alpha polypeptides and each subunit has a haem group that contains a Ferrous ion (Fe2+) has four haem groups, each carries one O2 molecule, when combined with oxygen makes oxyhaemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What must haemoglobin do to be efficient?

A

Readily associate with oxygen at the exchange surface, readily dissociate with oxygen at the tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is meant by affinity?

A

The attractive force binding atoms in molecules; chemical attraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is meant if haemoglobin has a high affinity?

A

Readily associates to oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is meant if haemoglobin has a low affinity?

A

Take up O2 less readily BUT release more readily (easily dissociates)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is the oxygen concentration at the exchange surface i.e the lungs?

A

High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the carbon dioxide concentration at the exchange surface i.e the lungs?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is the affinity for oxygen at the exchange surface i.e the lungs?

A

High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the result at the exchange surface i.e the lungs?

A

Oxygen is more readily associated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is the oxygen concentration at the respiring tissue i.e muscle?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the carbon dioxide concentration at the respiring tissue i.e muscle?

A

High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is the affinity for oxygen at the respiring tissue i.e muscle?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is the result at the respiring tissue i.e muscle?

A

Oxygen is more readily dissociated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What does affinity differ due to?

A

Metabolic rate and oxygen availability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is meant by the environment affecting the affinity for oxygen?

A

How much oxygen is available, partial pressure of oxygen (the amount of a gas present in a mixture of gases, measured in kPa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is meant by metabolic rate affecting affinity for oxygen?

A

How much oxygen is required by the organism, sum of chemical reactions in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What happens with haemoglobin if the environment has a low partial pressure of oxygen?

A

Need haemoglobin to hold onto oxygen, high affinity for oxygen, holds onto oxygen more tightly but means that oxygen will not be used as readily, organisms have a low metabolic rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What happens with haemoglobin if the environment has a high partial pressure of oxygen?

A

Oxygen is readily available, do not need to hold onto oxygen (weak attraction), low affinity for oxygen so oxygen dissociates easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is meant by partial pressure?

A

The amount of a gas present in a mixture of gases, how much pressure is caused by the molecule, measured in kPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Why is the first oxygen difficult to attach to haemoglobin?

A

Because of bonds and tight structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Why are the second and third oxygens easier to bind to haemoglobin?

A

Changed shape means can easily associate, disrupts bonds in the structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Why is the last oxygen difficult to attach to haemoglobin?

A

Fewer binding sites so difficult to fully saturate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Wha is an oxygen dissociation curve?

A

Shows the relationship between the saturation of haemoglobin and the partial pressure of oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What happens in stage one of an oxygen dissociation curve?

A

The saturation increases slowly because at low partial pressure it is difficult for the first oxygen to attach as there is less collisions as there is less oxygen, also because there is more bonds and a tight structure of haemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What happens in stage two of an oxygen dissociation curve?

A

The saturation increases rapidly as the first oxygen has disrupted the bonds, the changed shape means that oxygen can easily associate because of positive cooperativity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What happens in stage 3 of an oxygen dissociation curve?

A

There is only one binding site and a high partial pressure meaning there is more competition so it is difficult to fully saturate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What causes an oxygens dissociation curve to shift to the right?

A

Lower oxygen affinity, lower saturation or lower partial pressure, needs higher partial pressure for saturation, takes longer to become saturated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What causes an oxygen dissociation curve to shift to the left?

A

Higher affinity to oxygen so reaches saturation quicker, higher saturation at lower partial pressure, holds onto oxygen tightly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What happens when haemoglobin is exposed to different partial pressures of oxygen?

A

It does not absorb the oxygen evenly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What happens at very low concentrations of oxygen?

A

The four polypeptides of the haemoglobin molecule are closely united so it is difficult to absorb the first oxygen molecule, however this oxygen molecule causes the polypeptides to load the remaining oxygen molecules very easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What does the shape of an oxygen dissociation curve reveal?

A

A very small decrease in the partial pressure leads to a lot of oxygen becoming dissociated from haemoglobin, the graph tails off at very high oxygen concentrations because haemoglobin is almost saturated with oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what effect does carbon dioxide have on haemoglobin?

A

haemoglobin has a reduced affinity for oxygen in the presence of CO2- the greater the concentration of CO2, the more readily oxygen is released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

what is the Bohr effect?

A

explains why the behaviour of haemoglobin changes in different regions of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what does the Bohr effect say happens at the gas exchange surface?

A

at the gas exchange surface (e.g. the lungs), the level of carbon dioxide is low because it diffuses across the exchange surface and is expelled from the organism, the affinity of haemoglobin for oxygen is increased, which coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded to haemoglobin, the reduced CO2 level has shifted the oxygen dissociation curve to the left

66
Q

what does the Bohr effect say happens at rapidly respiring tissue?

A

in rapidly respiring tissues (e.g. muscles), the level of carbon dioxide is high, the affinity of haemoglobin for oxygen is reduced, which coupled with the low concentration of oxygen at the muscles, means that oxygen is readily unloaded into the muscle cells, the increased CO2 level has shifted the oxygen dissociation curve to the right

67
Q

why does the Bohr effect occur?

A

because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape

68
Q

what is the process of loading, transport and unloading of oxygen?

A

at the gas exchange surface carbon dioxide is constantly being removed, the pH is raised due to the low level of carbon dioxide, the higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily, this shape also increases the affinity for oxygen so it is not released while being transported, in the tissues carbon dioxide is produced by respiring cells, this lowers the pH changing the shape of haemoglobin to one that readily releases the oxygen to the respiration

69
Q

how does the process of loading, transport and unloading of oxygen ensure that there is always sufficient oxygen for respiring tissues?

A

the more active a tissue the more oxygen is unloaded; the higher the rate of respiration, the more CO2 produced, the lower the pH, the greater the haemoglobin shape change, the more readily oxygen is unloaded, the more oxygen is available for respiration

70
Q

how does the saturation of haemoglobin change through the body?

A

fully saturated at the lungs (four oxygen molecules), unloads one molecule at a tissue with a low respiratory rate (75% saturated), unloads three molecules at a very active tissue (25% saturated when returning to the lungs)

71
Q

how is water absorbed in plants?

A

by the roots through extensions called root hairs

72
Q

where is most water transported through in flowering plants?

A

thick walled tubes called xylem vessels

73
Q

what happens in the process of transpiration?

A

water is pulled through the xylem vessels through the evaporation of water from the leaves

74
Q

where does the energy come from for traspiration?

A

it is supplied by the sun making it a passive process

75
Q

how does water move out through the stomata?

A

the humidity of the atmosphere is usually less than the air spaces next to the stomata creating a water potential gradient from the air spaces through the stomata to the air, when the stomata are open, water vapour molecules diffuse out of the air spaces into the surrounding air, water lost by diffusion from the air spaces is replaced by water evaporating from the cell walls of the surrounding mesophyll cells, by changing the size of their stomatal pores plants can control the rate of transpiration

76
Q

how does water move in and out of mesophyll cells?

A

water is lost from mesophyll cells by evaporation from their cell walls to the air spaces of the leaf, this is replaced by water reaching the mesophyll cells from the xylem either via cell walls or via the cytoplasm

77
Q

why does water movement occur in the cytoplasmic route of transpiration?

A

mesophyll cells lose water to the air spaces by evaporation due to the heat supplied by the sun, these cells now have a lower water potential and so water enters via osmosis from neighbouring cells, the loss of water from these neighbouring cells lowers their water potential, they in turn take water from their neighbours by osmosis, in this way a water potential gradient is established that pulls water from the xylem, across the leaf mesophyll and finally out into the atmosphere

78
Q

what is the main factor responsible for the movement of water in the xylem?

A

cohesion-tension

79
Q

how does the movement of water occur in the stem?

A

water evaporates from mesophyll cells due to heat from the sun, leading to transpiration, water molecules form hydrogen bonds between one another and hence tend to stick together, this is known as cohesion, water forms a continuous, unbroken column across mesophyll cells and down the xylem, as water evaporates from the mesophyll cells in the leaf to the air spaces beneath the stomata, more molecules of water are drawn up behind as a result of this cohesion a column of water is therefore pulled up the xylem as a result of transpiration, this is called the transpiration pull, transpiration pull puts the xylem under tension , there is a negative pressure within the xylem hence the name cohesion-tension theory

80
Q

how does the changing diameter of tree trunks support the cohesion-tension theory?

A

change in the diameter of tree trunks according to the rate of transpiration, during the day, when transpiration is at its greatest there is more tension (more negative pressure) in the xylem, this pulls the walls of the xylem vessels inwards and causes the trunk to shrink in diameter, at night transpiration is lower so less tension causes the diameter of the trunk to increase

81
Q

what other evidence (apart from the diameter of tree trunks) is there to support the cohesion-tension theory?

A

if a xylem vessel is broken and air enters it, the tree can no longer draw up water, this is because the continuous column of water is broken and so the water molecules can no longer stick together. when a xylem vessel is broken, water does not leak out as would be the case if it were under pressure, instead air is drawn in which is consistent with it being under tension

82
Q

how is the xylem adapted for transpiration?

A

transpiration pull is a passive process and therefore does not require metabolic energy to take place, the xylem vessels are dead and therefore cannot actively move the water, xylem vessels have no end walls which means that xylem forms a series of continuous, unbroken tubes from root to leaves, which is essential to the cohesion-tension theory of water flow up the stem, energy is still needed for transpiration but this is in the form of heat from the sun to evaporate water from the leaves

83
Q

how are root hair cells adapted for their function?

A

thin cell wall, large surface area from long, hair like extensions, have mitochondria to create ATP for active transport

84
Q

what is osmosis?

A

the net movement of water molecules from an area of less negative to an area of more negative water potential through a selectively permeable membrane

85
Q

how are xylem vessels adapted for their function?

A

they have thick walls to prevent the vessels from collapsing, hollow, elongated, no cell surface membrane as they are dead, waterproofing,

86
Q

why can we measure the water uptake using a potometer?

A

about 99% of the water taken up by a plant is lost during transpiration, which means that the rate of uptake is almost the same as the rate of transpiration, we can then measure water uptake by the same shoot under different conditions (humidity’s, wind speed or temperatures) to get a reasonably accurate measure of the effects of these conditions on the rate of transpiration

87
Q

how is a potometer used to measure the rate of water loss in a plant?

A

a leafy shoot is cut under water, care is taken not to get water on the leaves, the potometer is filled completely with water, making sure there are no air bubbles, using a rubber tube, the leafy shoot is fitted to the potometer under water, the potometer is removed from under water and all joints are sealed with waterproof jelly, an air bubble is introduced into the capillary tube, the distance moved by the air bubble in a given time is measured multiple times to calculate a mean, once the air bubble nears the junction of the reservoir tube and the capillary tube, the tap on the reservoir is opened and the syringe is pushed down until the bubble is pushed back to the start of the scale on the capillary tube, measurements can continue as before, the experiment can be repeated to compare the rates of water uptake under different conditions

88
Q

how are results displayed for the potometer experiment?

A

using the mean value, the volume of water lost is calculated, the volume of water lost against time can be plotted in a graph

89
Q

what conditions can be investigated for the potometer practical?

A

different temperature, humidity, light intensity or the difference in water uptake between different species under the same conditions

90
Q

what is translocation?

A

the process by which organic molecules and some mineral ions are transported from one part of a plant to another

91
Q

what is the phloem?

A

the tissue that transports biological molecules in flowering plants, made up of sieve tube elements, long thin structures arranged end to end, their end walls are perforated to form sieve plates, companion cells are associated with sieve tube elements

92
Q

what are sources?

A

the sites of production of sugars through photosynthesis

93
Q

what are sinks?

A

the places where sugars will be directly used or stored for future use, can be located anywhere in the plant, above or below the source, so translocation can be in either direction

94
Q

which molecules does translocation include?

A

organic molecules such as sucrose and amino acids and inorganic ions such as potassium, chloride, phosphate, and magnesium

95
Q

where are sugars transported between during translocation?

A

from the source to the sink

96
Q

why can’t the transport of materials in the phloem be explained by diffusion?

A

it is too fast

97
Q

what is the current theory for the mechanism by which translocation is achieved?

A

the mass flow theory

98
Q

what are the three phases of the mass flow theory?

A

transfer of sucrose into sieve elements from photosynthesising tissue, mass flow of sucrose through sieve tube elements, transfer of sucrose from the sieve tube elements into storage or other sink cells

99
Q

what happens in the first phase of the mass flow theory (transfer of sucrose into sieve elements from photosynthesising tissue)?

A

sucrose is manufactured from the products of photosynthesis in cells with chloroplasts, the sucrose diffuses down a concentration gradient by facilitated diffusion from photosynthesising cells into companion cells, hydrogen ions are actively transported from companion cells into the spaces within cell walls using ATP, these hydrogen ions then diffuse down a concentration gradient through carrier proteins into the sieve tube elements, sucrose molecules are transported along with hydrogen ions in co-transport so the protein carriers are also co-transport proteins

100
Q

what happens in the second phase of the mass flow theory (mass flow of sucrose through sieve tube elements)?

A

the sucrose produced by photosynthesising cells is actively transported into the sieve tubes as described, this causes the sieve tubes to have a lower (more negative) water potential, as the xylem has a much higher (less negative) water potential, water moves from the xylem into the sieve tubes by osmosis creating a high hydrostatic pressure within them, at the respiring cells (sink), sucrose is either used up during respiration or converted into starch for storage, these cells therefore have a low sucrose content so sucrose is actively transported into them from the sieve tubes, lowering their water potential, meaning water moves into the respiring cells via osmosis, this lowers the hydrostatic pressure of the sieve tubes in this region, as a result of water entering the sieve tubes at the source and leaving at the sink, there is a high hydrostatic pressure at the source and a low one at the sink, there is therefore a mass flow of sucrose solution down this hydrostatic gradient in the sieve tubes

101
Q

what is mass flow?

A

the bulk movement of a substance through a given channel or area in a specified time

102
Q

why is mass flow affected by temperature and metabolic poisons?

A

because mass flow is a passive process but the process as a whole is active as it occurs as a result of the active transport of sugars

103
Q

what is the evidence for mass flow theory?

A

there is a pressure within the sieve tubes as shown by sap being released when cut, the concentration of sucrose is higher in leaves (source) than in roots (sink), downward flow in the phloem occurs in daylight but ceases when leaves are shaded at night, increases in sucrose levels in the leaf are followed by similar increases in sucrose levels in the phloem, metabolic poisons/lack of oxygen inhibit translocation of sucrose in the phloem, companion cells possess many mitochondria and readily produce ATP

104
Q

what is the evidence against mass flow theory?

A

the function of sieve plates is unclear as they would seem to hinder mass flow (it has been suggested that they provide structure and prevent tubes from bursting), not all solutes move at the same speed, they should do so if movement is by mass flow, sucrose is delivered more or less at the same rate to all regions, rather than going more quickly to the ones with the lowest sucrose concentration which is what the mass flow theory would suggest

105
Q

what happens in the third phase of the mass flow theory (transfer of sucrose from the sieve tube elements into storage or other sink cells)?

A

the sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells

106
Q

what is involved in a ringing experiment?

A

t of a ringing experiment, a section of the outer layer (protective layer and phloem) is removed around the complete circumference of a woody stem while it is still attached to the rest of the plant, after a period of time the region of the stem immediately about the missing ring of tissue swells, samples of the liquid accumulated in the swollen region are rich in sugars and other dissolved organic substances, some non-photosynthetic tissues below the ring wither and die while those above the ring continue to grow

107
Q

how are xylem and phloem arranged in woody stems?

A

woody stems have an outer protective layer of bark on the inside of which is a layer of phloem that extends all round the stem, inside the phloem layer is xylem.

108
Q

what do ringing experiments suggest that removing the phloem around the stem has led to?

A

the sugars of the phloem accumulating above the ring leading to swelling, the interruption of flow of sugars below the ring and the death of tissues here concludes that it is the phloem rather than xylem that is responsible for translocation of sugars in plants

109
Q

what happens in tracer experiments?

A

radioactive isotopes are useful for tracing the movement of substances in plants, for example the isotope carbon-14 can be used to radioactively label carbon dioxide (14CO2), if a plant is grown in an atmosphere containing 14CO2, the carbon-14 isotope will be incorporated into the sugars produced during photosynthesis, these radioactive sugars can be traced as they move within the plant using autoradiography, for example this could involve taking thin cross sections of the plant stem and placing them on a piece of x-ray film, the film becomes blackened where it has been exposed to the radiation produced by the carbon-14 in sugars, the blackened regions are found to correspond with where the phloem is in the stem, as the other tissues do not blacken the film, it follows that they do not carry sugars and that phloem alone is responsible for their translocation

110
Q

what is the evidence that translocation of organic molecules occurs in phloem?

A

when phloem is cut a solution of organic molecules flows out, plants provided with radioactive carbon dioxide can be show to have radioactively labelled carbon in phloem after a short time, aphids are a type of insect that feed on plant they have needle like mouthparts which penetrate the phloem, they can therefore be used to extract the contents of the sieve tubes, these contents show daily variations in the sucrose content of the leaves that are mirrored a little later by identical changes in the sucrose content of the phloem, the removal of a ring of phloem from around the whole circumference of a tem leads to the accumulation of sugars above the ring and their disappearence from below it

111
Q

where does the pulmonary artery take blood?

A

to the lungs

112
Q

where does the pulmonary vein take blood?

A

from the lungs to the heart

113
Q

where does the vena cava take blood?

A

from the body to the heart

114
Q

where does the aorta take blood?

A

to the body

115
Q

what are the three main blood vessels that make up the mammalian circulatory system?

A

arteries, capillaries and veins

116
Q

what features do blood vessels have?

A

tough outer layer, muscle layer, elastic layer, lumen (a cavity)

117
Q

what is the function of the tough outer layer of blood vessels?

A

resist pressure changes from both within and outside

118
Q

what is the function of the muscle layer of blood vessels?

A

contract to control flow of blood, maintains pressure

119
Q

what is the function of the elastic layer of blood vessels?

A

stretches and recoils to help maintain pressure

120
Q

what is the function of the lumen of blood vessels?

A

passage for the blood to travel through

121
Q

what are the features of arteries?

A

thick elastic layer, thick muscle layer, narrow lumen, high blood pressure, no valves

122
Q

what are the features of arterioles?

A

thinner elastic layer, thickest muscle layer, wider lumen than artery, low blood pressure, no valves

123
Q

what are the features of veins?

A

thin elastic layer, thin muscle layer, largest lumen, low blood pressure, has valves

124
Q

what are the features of capillaries?

A

no elastic layer, no muscle layer, very narrow lumen, very low blood pressure, no valves

125
Q

why does the artery have a much thicker elastic layer than veins?

A

to keep the blood pressure high, stretching at systole and springing back at diastole

126
Q

why do arteries have no valves but veins do?

A

blood is under high pressure in arteries but low pressure in veins so backflow is much more likely

127
Q

why do veins have a thinner muscle layer?

A

as carrying blood away from the tissues therefore constriction and dilation is not needed to control flow

128
Q

why are capillaries thin, branched and numerous?

A

the short diffusion pathway and increased surface area increases the rate of diffusion

129
Q

explain how the structure of the walls of arteries and arterioles are related to their function

A

elastic tissue stretches under pressure and then recoils which evens out pressure, the muscle wall contracts causing vasoconstriction which changes the flow, the epithelium is smooth to reduce friction

130
Q

what is the function of veins?

A

carry blood towards the heart

131
Q

what is the function of venules?

A

control blood flow from capillaries to veins

132
Q

what is the function of capillaries?

A

link arterioles to veins

133
Q

what is the function of arterioles?

A

control blood flow from arteries to capillaries

134
Q

what is the function of arteries?

A

carry blood away from the heart

135
Q

when does the cardiac cycle start?

A

when the SAN sends an electrical wave to the septum (base), via the atrium

136
Q

what is the SAN node?

A

the heart’s pacemaker, initiates an electrical wave of activity

137
Q

what is the AVN?

A

the second node for contraction, initiates an electrical wave down the septum

138
Q

what are the three waves shown by ECGs?

A

p wave (atrial systole, contraction is weaker), PR (delay from SAN to AVN), QRS complex (ventricular systole, stronger contraction), T wave (ventricular diastole)

139
Q

how do you calculate cardiac output?

A

cardiac output = heart rate x stroke volume

140
Q

why can individuals survive healthily despite having differing resting heart rates?

A

they have increased muscular wall of the heart and improved the affinity of haemoglobin so require less blood

141
Q

what is cardiovascular disease?

A

degenerative diseases of the heart and circulatory system

142
Q

what are examples of cardiovascular disease?

A

strokes, angina, heart attacks/failure, atherosclerosis

143
Q

what is meant by degenerative?

A

causes a decline in health/situation declines

144
Q

what is a risk factor?

A

any characteristic or exposure of an individual that increases the likelihood of developing a disease or injury (not causes)

145
Q

what is meant by correlation?

A

a change in one of two variables is reflected in the other, risk factors are correlations

146
Q

what is tissue fluid?

A

a water liquid that bathes all of the tissues in our body, allows the exchange of substances between the blood and cells, contains molecules required and the waste produced, unlike the blood it does not contain large molecules (red blood cells, plasma proteins)

147
Q

which molecules required does tissue fluid contain?

A

glucose, amino acids, fatty acids, ions, oxygen

148
Q

which waste products does tissue fluid contain?

A

carbon dioxide, urea, water

149
Q

what does the blood contain that tissue fluid does not?

A

large molecules such as red blood cells, plasma proteins

150
Q

which two pressures is the formation of tissue fluid a result of the balance between?

A

hydrostatic pressure and water potential (osmotic pressure)

151
Q

what is hydrostatic pressure?

A

result of the heart pumping, forces small molecules out and prevents the movement of liquid in, become narrower = pressure increases

152
Q

how is tissue fluid formed?

A

hydrostatic pressure inside the capillary is greater, fluid from the blood is forced out of the capillaries, blood contains plasma proteins that lower the water potential, some water moves into capillaries from tissue fluid, hydrostatic pressure can only force small molecules out of the capillary so larger molecules and proteins remain in the blood, this type of filtration is known as ultra filtration

153
Q

how is waste returned into the blood from the tissue fluid?

A

tissue fluid must then return to the blood plasma to remove waste, water potential is lower inside the capillary so water moves back in, hydrostatic pressure is reduced at the venule end so tissue fluid containing waste products is forced back in

154
Q

what happens at the arteriole end (tissue fluid)?

A

higher hydrostatic pressure, lower osmotic pressure, net loss of water/fluid out, tissue fluid is formed

155
Q

what happens at the venule end (to the veins) with tissue fluid?

A

lower hydrostatic pressure, higher osmotic pressure, net movement in, removal of waste

156
Q

what percentage of tissue fluid enters the lymphatic system?

A

10%

157
Q

what is the lymphatic system?

A

separate to the circulatory system, made up of lymph capillaries, contains accumulated tissue fluid (lymph), drains back into the blood via two ducts that join veins close to the heart

158
Q

how is lymph moved?

A

by hydrostatic pressure of tissue fluid, contraction of body muscles squeezes lymph vessels

159
Q

what is the fluid in the blood?

A

plasma

160
Q

what is the fluid that surrounds cells?

A

tissue fluid

161
Q

what is the fluid in the lymphatic system?

A

lymph

162
Q

How are sieve cells adapted for mass transport?

A

Few or no organelles, not much cytoplasm, does not have to diffuse/be actively transported through organelle,large vacuoles, more space for mass flow to occur, thick cell walls to withstand pressure created by mass flow

a level biology (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions