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A-Level Biology - AQA > ✅7 - Mass Transport > Flashcards

✅7 - Mass Transport Flashcards

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1
Q

What is associating?

A

When haemoglobin binds with oxygen

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2
Q

Where does loading take place?

A

In the lungs

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3
Q

What is dissociating?

A

When haemoglobin releases its oxygen

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4
Q

Where does unloading take place?

A

The tissues

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5
Q

Haemoglobins with a high affinity for oxygen…

A

…take it up easily but release it less easily

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6
Q

Haemoglobins with a low affinity for oxygen…

A

…don’t take it up easily but release it easily

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7
Q

What is the role of haemoglobin?

A

To transport oxygen

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8
Q

What features must haemoglobin have to be efficient at transporting oxygen?

A

Readily dissociate with oxygen at the surface where gas exchange occurs
Readily dissociate from oxygen at the tissues requiring it

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9
Q

When does haemoglobin change affinity?

A

Under different conditions, such as O2 and CO2 concentrations

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10
Q

Why do different haemoglobins have different affinities for oxygen?

A

Because they have different shapes as each species produces a different amino acid sequence so the tertiary and quaternary structure are different

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11
Q

What is an oxygen dissociation curve?

A

The graph of the relationship between the saturation of haemoglobin and oxygen partial pressure

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12
Q

At low oxygen concentrations, why does little oxygen bind to haemoglobin?

A

Because the shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits because they are closely united

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13
Q

Why is it easier for the second oxygen molecule to bind to haemoglobin?

A

Because the binding of the first oxygen molecule changes the quaternary structure of the haemoglobin and makes it easier for other subunits to bind to an oxygen molecule

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14
Q

What is positive cooperativity?

A

Binding the first molecule makes binding of the second easier and so on

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15
Q

What happens after the binding of the third oxygen molecule?

A

It is harder to bind the fourth, as the majority of the binding sites are filled and it is less likely that a single oxygen molecule will find an empty site to bind to

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16
Q

What is the shape of the oxygen dissociation curve?

A

Sigmoidal

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17
Q

The further the curve is to the left…

A

…the greater the affinity of haemoglobin for oxygen

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18
Q

The further the curve is to the right…

A

…the lower the affinity of haemoglobin for oxygen

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19
Q

How does haemoglobin’s affinity for oxygen change in the presence of carbon dioxide?

A

Its affinity is reduced

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20
Q

What is the Bohr effect?

A

The greater the concentration of Carbon Dioxide, the more rapidly haemoglobin releases its oxygen

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21
Q

Why is a transport system required?

A

To take materials from cells to exchange surfaces and the environment

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22
Q

What factors does the presence of a transport system depend on?

A

The surface area to volume ratio

How active an organism is

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23
Q

What are the features of transport system?

A

A suitable medium in which to carry materials
A form of mass transport
A closed system of tubular vessels
A mechanism for moving the transport medium within vessels

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24
Q

What do animals use as transport mechanisms?

A

Muscular contraction either of the body muscles or of the organs eg heart

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25
Q

What do plants rely on for exchange?

A

Natural, passive processes such as evaporation

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26
Q

What kind of circulatory system to mammals have?

A

A closed, double system

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27
Q

Why does the blood pass through the heart twice for reach circuit of the body?

A

Because pressure is reduced when the blood is passed through the lungs, and it otherwise would circulate the body very slowly

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28
Q

What is the atrium?

A

A thin walled and elastic chamber which stretches as it collects blood

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29
Q

What is the ventricle?

A

A much thicker, more muscular chamber

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30
Q

Why do the ventricles have thicker more muscular walls?

A

Because they have to contract strongly to pump blood a further distance

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31
Q

Where does the right ventricle pump blood to?

A

The lungs

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32
Q

Where does the left ventricle pump blood to?

A

The rest of the body

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33
Q

What are the two valves?

A

The left atrioventricular (bicuspid)

The right atrioventricular (tricuspid)

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34
Q

What is the problem with the large surface area needed for the capillaries in the lungs?

A

There has to be a significant drop in pressure

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35
Q

What is the aorta connected to?

A

The left ventricle

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36
Q

What does the aorta do?

A

Carries oxygenated blood to all parts of the body except the lungs

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37
Q

What is the vena cava connected to?

A

The right atrium?

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38
Q

What does the vena cava do?

A

Brings deoxygenated blood back from the tissues of the body

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39
Q

What is the pulmonary artery connected to?

A

The right ventricle

40
Q

What does the pulmonary artery do?

A

Carried deoxygenated blood to the lungs where it is replenished with oxygen and carbon dioxide removed

41
Q

What is the pulmonary vein connected to?

A

The left atrium

42
Q

What does the pulmonary vein do?

A

Brings oxygenated blood back from the lungs

43
Q

Which blood vessels supply the heart?

A

The coronary arteries

44
Q

What is a myocardial infarction?

A

A heart attack

45
Q

Where do the coronary arteries branch off from?

A

The aorta

46
Q

What is systole?

A

Contraction

47
Q

What is diastole?

A

Relaxation

48
Q

What happens in diastole?

A

Blood returns to atria, pressure rises. AV valves open, blood passes into ventricles, pressure drops and semi lunar valves close

49
Q

What happens in atrial systole?

A

Contraction of atrial walls forces blood into ventricles from atria

50
Q

What happens in ventricular systole?

A

Ventricles fill with blood, wall contract, increasing pressure. AV valves shut and backflow prevented. Blood forced out into arteries

51
Q

Where are the atrioventricular valves located?

A

Between the left atrium and ventricle and the right atrium and ventricle

52
Q

What do the atrioventricular valves do?

A

Prevent backflow of blood when contraction of ventricles means that ventricular pressure exceeds atrial pressure

53
Q

Where are the semi-lunar valves?

A

In the aorta and pulmonary artery

54
Q

What do the semi-lunar valves do?

A

Prevent backflow of blood into ventricles when pressure in the vessels exceeds the pressure in the ventricles

55
Q

Where are the pocket valves?

A

In veins

56
Q

What is cardiac output?

A

The volume of blood pumped by one ventricle of the heart in one minute?

57
Q

How would you calculate cardiac output?

A

heart rate x stroke volume

58
Q

What do arteries do?

A

Carry blood away from the heart to the arterioles

59
Q

What do arterioles do?

A

Smaller arteries that control the blood flow from arteries to capillaries

60
Q

What do capillaries do?

A

Tiny vessels that link arterioles to veins

61
Q

What do veins do?

A

Carry blood from capillaries back to the heart

62
Q

What is the basic structure of arteries, arterioles and veins?

A 
Tough fibrous outer layer
Muscle layer
Elastic layer
Thin inner lining
Lumen
63
Q

What is the function of the tough fibrous layer?

A

Resists pressure changes from both within and outside

64
Q

What is the function of the muscle layer?

A

Can contract and so control the flow of blood

65
Q

What is the function of the elastic layer?

A

Helps maintain blood pressure by stretching and springing back

66
Q

What is the function of the thin inner lining?

A

Smooth to reduce friction and thin to allow diffusion

67
Q

What is the function of the lumen?

A

The central cavity, allows blood to flow

68
Q

How are arteries adapted to their function?

A

Thick muscle layer to constrict and dilate
Thick elastic layer to come with high blood pressure
Thick wall to resist pressure
No valves

69
Q

How are arterioles adapted for their function?

A

Muscle layer is thicker to allow constriction

Thin elastic layer because blood pressure is lower

70
Q

How are veins adapted for their function?

A

Muscle layer is relatively thin as constriction and dilation can’t control blood flow
Elastic layer is thin due to low pressure
Overall thickness is small, low pressure
Valves throughout

71
Q

How are capillaries adapted for their function?

A

Walls consist mostly of the lining layer
Numerous and highly branched
Narrow diameter to permeate tissues
Narrow lumen to squeeze RBCs flat

72
Q

What is tissue fluid?

A

A watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen

73
Q

How is tissue fluid formed?

A

High hydrostatic pressure at the artery end forces the fluid out through the capillary

74
Q

What is ultrafiltration?

A

Filtration under pressure

75
Q

How is tissue fluid returned to the circulatory system?

A

The loss of tissue fluid reduces hydrostatic pressure in capillaries, so higher hydrostatic pressure outside forces fluid back in. Water also leaves the tissue by osmosis.

76
Q

How are fluids moved around the body?

A

Hydrostatic pressure o the tissue fluid

Contraction of body muscles

77
Q

How does water move across the cells of the leaf?

A

Water from mesophyll cells is lost by evaporation from their cell walls to the air spaces in the leaf, then water moves by osmosis into the drier cells

78
Q

What is the main factor responsible for the movement of water up the xylem?

A

Cohesion tension

79
Q

How does water move up the xylem?

A

Water evaporates from mesophyll
Water molecules form hydrogen bonds and have cohesion
Water forms a continuous column down the xylem
The column is pulled up the xylem

80
Q

What is transpiration pull?

A

When a column of water is pulled up the xylem as a result of transpiration

81
Q

What evidence supports cohesion-tension theory?

A

Tree trunks change in diameter according to the rate of transpiration
If a xylem vessel is broken and air enters, a tree can no longer take up water
When a xylem vessel is broken, water does not leak out as it would if it was under pressure

82
Q

What is needed to drive the process of transpiration?

A

Energy from the sun

83
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

84
Q

What is the phloem?

A

The tissue that transports biological molecules in flowering plants

85
Q

What are sources?

A

The sites of production of sugars

86
Q

What are sinks?

A

The site of use or storage of sugars

87
Q

What are the three stages of 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

88
Q

What happens in transfer of sucrose into sieve elements?

A

Sucrose diffuses down a concentration gradient into companion cells from photosynthesising ones
Hydrogen ions actively transported using ATP into the companion cells
H+ diffuse down conc gradient into sieve tube elements
Co transport of sucrose with H+

89
Q

What happens in the mass flow of sucrose through sieve tube elements?

A

Sucrose produced by source is actively transported into sieve tubes
Causes sieve tubes to have lower water potential
Water moves from xylem into sieve tubes by osmosis, creating high hydrostatic pressure
Sucrose and water actively enter sink due to low water potential and sucrose concentration
High hydrostatic pressure at source and low at sink causes mass flow of sucrose solution down gradient

90
Q

What evidence supports mass flow theory?

A

There is a pressure within sieve tubes, shown by release of sap
Concentration of sucrose is higher in leaves (source) than roots (sink)
Downwards flow in phloem occurs in daylight but not at night

91
Q

What evidence goes against the theory?

A

Function of sieve plates in unclear as they would seem to hinder mass flow
Not all solutes move at the same speed, they should do if the movement is by mass flow

92
Q

What happens in transfer of sucrose from sieve tube elements into sink?

A

Sucrose is actively transported by companion cells out of sieve tubes and into sink cells

93
Q

How can ringing be used to investigate mass transport in plants?

A

When woody stems are ringed, the upper region is seen to swell and the sap is seen to be rich in sugars and dissolved substances

94
Q

What do ringing experiments show?

A

That the phloem is responsible for transport of sugars rather than they xylem

95
Q

How can radioactive isotopes be used to investigate mass transport in plants?

A

Radioactively labelled CO2 can be used as it will be taken up by the plant and then incorporated into sugars. They can then be traced

96
Q

What is evidence for the fact that translocation occurs in the phloem?

A

When phloem is cut, a solution of organic molecules flows out
Plants provided with radioactive carbon dioxide can be shown to have radioactively labelled phloem

A-Level Biology - AQA (22 decks)

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