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A-level Biology Longridge Towers School > Chapter 7 Mass Transport > Flashcards

Chapter 7 Mass Transport Flashcards

1
Q

Why do larger organisms require a circulatory system?

A

All cells require a constant supply of oxygen and glucose. Single celled organisms can access these through diffusion. Larger organisms have too many layers of cells to be able to use diffusion. The diffusion distances are too great and it would take too long. A mass transport system like a circulatory system delivers substances like oxygen and glucose to cells while removing waste products.

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2
Q

What is mass transport?

A

The bulk movement of liquids or gases in one direction.

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3
Q

What type of protein is haemoglobin?

A

Globular protein.

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4
Q

How many polypeptide chains make up a haemoglobin molecule?

A

4

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5
Q

What does haemoglobin transport?

A

Oxygen

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6
Q

What is the primary structure of haemoglobin?

A

The order of amino acids in the polypeptide chains.

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7
Q

What is the secondary structure of haemoglobin?

A

The coiling of the polypeptide chains into a helix

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8
Q

What is the tertiary structure of haemoglobin?

A

The folding of the polypeptide chains into a precise shape through ionic bonds, hydrogen bonds, and disulfide bridges.

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9
Q

What is the quaternary structure of haemoglobin?

A

The linking of the 4 polypeptide chains into an almost spherical molecule. Each polypeptide chain also has an associated haem group.

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10
Q

What ion does a haem group contain?

A

Fe2+

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11
Q

How many oxygen molecules does each Fe2+ ion combine with?

A

1 oxygen per Fe2+

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12
Q

How many oxygen molecules can a molecule of haemoglobin carry in humans?

A

4, one per Fe2+ ion in each haem group. 1 haem group in each polypeptide chain. 4 polypeptide chains.

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13
Q

What is the chemical equation for the binding of oxygen to haemoglobin?

A

Oxygen + Haemoglobin ⇄ Oxyhaemoglobin
4O2 +Hb ⇄ Hb4O2

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14
Q

What names are given to the process by which haemoglobin binds with oxygen?

A

Loading or associating.

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15
Q

What names are given to the process by which haemoglobin releases oxygen?

A

Unloading or dissociating.

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16
Q

What does affinity mean with respect to haemoglobin?

A

Affinity is the relative attraction of haemoglobin to oxygen.

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17
Q

If haemoglobin has high affinity, what does this mean?

A

Easier to take in oxygen, harder to lose oxygen.

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18
Q

If haemoglobin has a low affinity, what does this mean?

A

Harder to take in oxygen, easier to lose oxygen.

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19
Q

To be good at transporting oxygen, what 2 characteristics must haemoglobin have?

A

It must readily associate with oxygen where gas exchange occurs.

It must readily dissociate from oxygen in tissues which require it.

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20
Q

What happens to haemoglobin’s affinity for oxygen when carbon dioxide binds?

A

Haemoglobin will change shape when in the presence of carbon dioxide (and certain other molecules). Once the shape changes the affinity for oxygen reduces so it is easily dissociated.

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21
Q

What do we mean by partial pressure?

A

The pressure exerted by one component of a mixture of gases, if it alone occupied the volume. E.g. Atmospheric pressure is 100kPa. Oxygen is 21% of the atmosphere. It’s PP is 21kPa.

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22
Q

What does a dissociation curve represent?

A

It is a graph relating the partial pressure of oxygen, and how saturated the haemoglobin is with oxygen.

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23
Q

What shape does the oxygen dissociation curve take?

A

S

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24
Q

Why does the oxygen dissociation curve increase slowly to begin with?

A

The shape of the haemoglobin molecule makes binding the first oxygen molecule difficult.

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25
Q

Why does the oxygen dissociation curve increase sharply after a slow beginning?

A

The first oxygen molecule to bind changes the shape of the quaternary structure. This makes binding of subsequent molecules easier.

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26
Q

Why does the oxygen dissociation curve increase slowly at the end of the graph?

A

Probability. It is easier for the molecules to bind, but the likelihood of the 4th oxygen molecule to find an empty binding site is less likely.

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27
Q

What is the name given to the increase in ease of binding for 2nd, 3rd, 4th oxygen molecules?

A

Positive cooperativity.

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28
Q

If an oxygen dissociation curve is shifted to the left, how does that affect the affinity for oxygen?

A

Higher affinity for oxygen, loads more easily, unloads reluctantly.

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29
Q

If an oxygen dissociation curve is shifted to the right how does that affect the affinity for oxygen?

A

Lower affinity for oxygen, loads less readily, unloads easier.

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30
Q

What effect does carbon dioxide have on the affinity of haemoglobin?

A

The higher the concentration of carbon dioxide, the lower the affinity of haemoglobin to oxygen. Haemoglobin releases oxygen more readily.

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31
Q

What effect does a higher concentration of carbon dioxide have on the oxygen dissociation curve?

A

It is shifted to the right.

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32
Q

What effect does a lower concentration of carbon dioxide have on the oxygen dissociation curve?

A

It is shifted to the left.

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33
Q

What is the name given to the shifting of the dissociation curve due to carbon dioxide?

A

Bohr effect.

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34
Q

What effect does the Bohr effect have at the gas exchange surface?

A

In low carbon dioxide concentrations, the affinity of haemoglobin for oxygen is increased, and the curve is shifted to the left.

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35
Q

What effect does the Bohr effect have at the respiring tissues?

A

In high carbon dioxide concentrations, the affinity of haemoglobin for oxygen is decreased, and the curve is shifted to the right.

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36
Q

Why does carbon dioxide cause the haemoglobin to lose oxygen more readily?

A

Dissolved carbon dioxide is acidic. The low pH causes the haemoglobin to change shape.

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37
Q

How might the oxygen dissociation curve appear for an animal adapted to live in an area with a very low pp of oxygen?

A

They would require haemoglobin with a higher oxygen affinity, so the curve would be further to the left

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38
Q

How is the heart described (in terms of being a pump)

A

A double pump

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39
Q

What does the left side of the heart deal with?

A

Oxygenated blood from the lungs

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40
Q

What does the right side of the heart deal with?

A

Deoxygenated blood from the body

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41
Q

Name the two chambers in each pump?

A

An atrium and a ventricle.

42
Q

Describe the structure and role of the atria?

A

Atria are thin walled and elastic. The wall stretches as blood enters.

43
Q

Describe the structure and role of the ventricles?

A

Ventricles have thick muscular walls to pump blood a good distance (Lung or body).

44
Q

Why is the heart a double pump system?

A

As the blood flows through the capillaries of the lungs, there is a massive drop in pressure. This would decrease the speed at which the blood would flow through the rest of the body. A second pump is required.

45
Q

What valve separates the left atrium and ventricle?

A

The left atrioventricular (bicuspid) valve.

46
Q

What valve separates the right atrium and ventricle?

A

The right atrioventricular (tricuspid) valve.

47
Q

Which chamber has the thickest walls and why?

A

The left ventricle is thicker because it has to pump blood through the aorta at high pressure all round the body.

48
Q

What supplies the blood to the heart?

A

Coronary arteries.

49
Q

What happens if the coronary arteries are blocked?

A

Myocardial infarction (heart attack) as the muscle cells have no oxygen so die as are unable to respire aerobically.

50
Q

The contraction of the atria is known as…?

A

Atrial systole.

51
Q

The relaxation of the heart is called…

A

Diastole.

52
Q

Contraction of the ventricles is known as…

A

Ventricular systole.

53
Q

What is the main job of valves?

A

To prevent the backflow of blood.

54
Q

How do the atrioventricular valves close?

A

As the ventricles contract, the ventricular pressure exceeds atrial pressure.

55
Q

Where are the semilunar valves?

A

Semilunar valves are found in the aorta and the pulmonary artery.

56
Q

How do the semilunar valves close?

A

When the elastic walls of the arteries recoil, it causes the pressure to exceed that of the relaxed ventricle. This forces blood through the artery.

57
Q

What are pocket valves?

A

These are valves located through the venous system.

58
Q

How do pocket valves close?

A

When the skeletal muscles contract, and the veins are squeezed, the valves only allow blood to flow towards the heart.

59
Q

How do you calculate cardiac output?

A

Cardiac output = Heart rate x Stroke volume

60
Q

What are the 4 types of blood vessels?

A

Arteries

Arterioles

Capillaries

Veins

61
Q

What is the 2nd most inner layer found in both arteries and veins called?

A

The elastic layer.

62
Q

What is one adaptation of arteries which allows them to withstand high pressures?

A

Thick elastic tissue that allows them to expand under high pressure.

63
Q

Which blood vessel carries blood from the heart to the body?

A

Aorta

64
Q

Which blood vessel carries blood from the body to the heart?

A

Vena cava

65
Q

Which blood vessel carries blood from the body to the kidneys?

A

Renal artery

66
Q

Which blood vessel carries blood from the kidneys to the vena cava?

A

Renal vein

67
Q

Which blood vessel carries blood from the heart to the lungs?

A

Pulmonary artery

68
Q

Name 5 substances that are found within tissue fluid.

A

Glucose

Amino acids

Fatty acids

Ions in solution

Oxygen.

69
Q

Describe how tissue fluid is returned to the circulatory system.
(5 stages)

A

Loss of tissue fluid causes a drop in hydrostatic pressure.

Therefore at the venous end of the capillary network pressure is lower than the tissue fluid outside.

Fluid is forced back in.

Also plasma which has lost water has a lower water potential.

Water moves from tissue fluid down a water potential gradient

70
Q

How does water move up the stem of a plant?

A

Cohesion-tension

71
Q

How is water lost through a leaf?

A

Water is lost by transpiration through stomata.

72
Q

How is water lost through the stomata?

A

Diffusion. The humidity of the atmosphere is lower than that inside the leaf.

73
Q

How does water move through the cells of a leaf?

A

Mesophyll cells lose water through evaporation into the air spaces.
This lowers their water potential causing movement of water via osmosis from neighbouring cells due to water potential difference.

74
Q

How does water move up the stem in the xylem?

A

Water evaporates from the mesophyll.
The hydrogen bonds between water molecules cause cohesion joining water molecules to each other.
Water makes a continuous chain from the mesophyll down the xylem.
The loss of water draws up new water molecules through the xylem.
This is called transpiration pull.

75
Q

What is the cohesion-tension theory?

A

The idea that the xylem is under tension, as the pull from transpiration puts them under negative pressure.

76
Q

Give 3 pieces of evidence for the cohesion - tension theory.

A

Change in the diameter of tree trunks based on the rate of transpiration.

If air enters the xylem, transpiration no longer occurs as there is no continuous column of water.

Water doesn’t leak out if the xylem is broken. The negative pressure draws air in instead.

77
Q

Why is transpiration pull a passive process?

A

It occurs due to evaporation so requires no metabolic energy.

78
Q

Where does the energy come from to drive the process of transpiration?

A

The sun.

79
Q

When talking about the movement of water in plants, what is the cell wall pathway (sometimes called the apoplast pathway)?

A

The cell wall pathway is the movement of water around the cells, through the cell walls (water doesn’t enter the cells.

80
Q

When talking about the movement of water in plants, what is the cytoplasmic pathway?

A

The movement of water through the cells via osmosis as the water potential changes.

81
Q

Does sucrose affect water potential and if so how does the plant combat this?

A

Sucrose lowers water potential in the phloem sieve tubes, water moves from the xylem to sieve tubes.

82
Q

What is a potometer?

A

A piece of equipment used to measure the movement of water into a plant.

83
Q

What is it that moves in a potometer?

A

Water moves through the potometer, this is observed by trapping an air bubble which is drawn through a capillary tube.

84
Q

Why is the plant to be investigated, cut underwater?

A

So as not to get air trapped in the xylem vessels

85
Q

What is measured when using a potometer?

A

The movement of a trapped air bubble along a capillary tube, and the time taken. Then the volume of water taken in by the plant can be calculated, and the time taken used to calculate the rate of uptake as well.

86
Q

What are assimilates?

A

Assimilates are substances that will become part of biological molecules (example: sucrose).

87
Q

What is translocation with respect to the phloem?

A

Translocation within phloem is the transport of assimilates from source to sink and requires ATP.

88
Q

How does sucrose enter the sink from the phloem?

A

Active transport

89
Q

How is sucrose moved from the source to the sieve elements?

A

Diffuses down the concentration gradient by facilitated diffusion into companion cells.

H+ ions are actively transported out of companion cells.

H+ ions and sucrose molecules are transported into sieve tube elements by co-transport.

90
Q

How is sucrose moved through the sieve elements?

A

Sucrose that moves in at the source (leaf cell). This decreases water potential.

Water moves in from the xylem.

At the sinks (root cell), sucrose moves into the respiring cells, as does water.

This creates a hydrostatic pressure difference, so the sucrose solution is forced from source to sink.

91
Q

How is sucrose moved from the sieve elements to the storage or sink cells?

A

Active transport from sieve to sink by the companion cells

92
Q

Why is mass flow described as passive?

A

It does not use metabolic energy to directly move the substances.

93
Q

Is translocation active or passive? Why?

A

It is active, as it is driven by the active transport of sugars.

94
Q

In a woody stem, what lies just under the bark?

A

The phloem.

95
Q

What happens in a ringing experiment?

A

A complete ring of bark and phloem is removed from the stem.

96
Q

What would you observe after a ringing experiment?

A

There is a swollen region in the bark just above where the ring of stripped stem is.

97
Q

What happens to the parts of the plant above and below the stripped area of bark in a ringing experiment?

A

The non-photosynthetic parts below the ring start to die. Those above stay alive.

98
Q

How does removing the phloem affect the plant? What does it mean?

A

Sugars accumulate above the ring causing the swelling.
The interruption of the sugars cause the parts below the ring to die.
It shows that the phloem, not the xylem, is involved in the movement of sugars.

99
Q

What is an isotope?

A

An element with the same number of protons and electrons, but a different number of neutrons.

100
Q

What are radioactive isotopes used for in plant investigations?

A

They can be used to trace the movement of these isotopes and the substances they become through the plant.

101
Q

What is an example of a radioactive isotope? What happens to it in a plant?

A

14C is different from a typical 12C. It can be converted to CO2 which is then used in the plant to create sugars.

102
Q

What can be used to identify the presence of the radioisotopes?

A

X-Ray film. It will be blackened when exposed to the radiation.

A-level Biology Longridge Towers School (37 decks)

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