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

Chapter 7 - Mass Transport Flashcards

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1
Q

Where is haemoglobin found?

A

Inside red blood cells

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2
Q

What is haemoglobin made from?

A

Protein

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3
Q

What type of structure does haemoglobin have?

A

Quaternary

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4
Q

What is the primary structure of haemoglobin?

A

The sequence of amino acids in the four polypeptide chains

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5
Q

What is the secondary structure of haemoglobin?

A

Each of the polypeptide chains are made into a helix

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6
Q

How many polypeptide chains are there in haemoglobin?

A

4

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7
Q

What is the tertiary structure of haemoglobin?

A

Each polypeptide chain is folded into a precise shape

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8
Q

What is the quaternary structure of haemoglobin?

A

The four polypeptide chains are linked together. Each polypeptide chain is associated with a haem group (a Fe2+ ion) and so the molecule can carry 4 oxygen molecules

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9
Q

What does a haem group contain?

A

A ferrous (Fe2+) ion

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10
Q

What is the name of the process of binding with oxygen?

A

Loading (or associating)

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11
Q

What is the name of the process of haemoglobin releasing oxygen?

A

Unloading (or dissociating)

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12
Q

Where does association with oxygen take place?

A

Lungs

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13
Q

Where does dissociation of oxygen take place?

A

Tissues

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14
Q

What does affinity mean?

A

Look in text book 😞😮😭🤣🤣😉🙏😬😉😭😭🤣

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15
Q

Does haemoglobin have a high or low affinity for oxygen?

A

High - it combines with it easily but releases it less easily

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16
Q

What does haemoglobin form when it associated with oxygen?

A

Oxyhaemoglobin

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17
Q

What properties does haemoglobin have that makes it successful at transporting oxygen?

A

It readily binds to oxygen in the lungs and readily dissociates with oxygen in the tissues

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18
Q

How does haemoglobin obtain its contradicting properties?

A

Its tertiary structure (and so, therefore, the shape of active site) change under certain conditions, like carbon dioxide concentration

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19
Q

What is partial pressure?

A

A measure of oxygen concentration

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20
Q

When will oxyhaemoglobin release its oxygen?

A

When there is a low concentration of oxygen

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21
Q

Why do different haemoglobins have different affinities for oxygen?

A

The DNA base sequence differs between species. As a result of this, the mRNA and tRNA sequences will be different too. Therefore, the amino acid sequence constructed by the ribosome will be different. Bonds will form in different places and so the tertiary and quaternary structures will be different. This impacts the haemoglobin’s ability to bind to oxygen

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22
Q

Whats is an oxygen dissociation curve?

A

It shows how saturated haemoglobin is with oxygen at any given partial pressure

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23
Q

Why is the gradient of the oxygen dissociation curve shallow initially?

A

At low oxygen concentrations, the haemoglobin has a low affinity for oxygen (so it releases it rather than associating with it). This is because it changes its shape to make it harder for oxygen to bind to it

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24
Q

What happens once the first molecule of oxygen has bonded to the haemoglobin?

A

The binding of the oxygen molecule makes the haemoglobin change its shape so that is easier for the other haem groups to bind to an oxygen molecule

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25
Q

Why does the gradient of the oxygen dissociation curve steepen?

A

Once the first molecule of oxygen has bound to the haemoglobin, it only takes a small increase in partial pressure to bind the second molecule. This is an example of positive cooperativity (binding the first makes the second easier and so on)

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26
Q

Why does the gradient of the oxygen dissociation curve level out?

A

Probability - three of the binding sites are occupied so the probability of an oxygen molecule binding with the fourth is small

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27
Q

What does an oxygen dissociation curve that is further to the left show?

A

The greater the affinity for oxygen (loads easily, unloads with difficulty)

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28
Q

What does an oxygen dissociation curve that is further to the right show?

A

The lower the affinity for oxygen (loads with difficulty, unloads easily)

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29
Q

Why does a mouse’s haemoglobin have a lower affinity for oxygen?

A

It has a high surface area to volume ratio so loses heat easily. This means it must have a high metabolic rate (and therefore require lots of aerobic respiration to create energy)

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30
Q

Why might the affinity of haemoglobin of a carp be higher than that of a mackerel?

A

The carp is found in deep, freshwater lakes where there isn’t much oxygen, whereas the mackerel lives at the surface of the lake where there is lots of oxygen

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31
Q

What is the Bohr effect?

A

When cells respire, they release CO2
This reduces the partial pressure of oxygen
This increases the rate of oxygen unloading and so the dissociation curve shifts to the right. More CO2 is released

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32
Q

Why would the oxygen dissociation curve at the lungs be shifted to the left?

A

The concentration of CO2 is low because it is excreted from the lungs. The affinity of haemoglobin increases because of the high concentration of oxygen in the lungs, shifting the curve to the left

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33
Q

Why would the dissociation curve for the muscles be shifted to the right?

A

The concentration of CO2 is high because of the increased levels of respiration. The affinity of haemoglobin and the concentration of oxygen is lower, which means oxygen is easily unloaded into muscle cells, shifting the curve to the right

34
Q

Why does carbon dioxide change the shape of a haemoglobin molecule?

A

Dissolved CO2 is acidic and the low pH changes the shape of haemoglobin by breaking bonds

35
Q

How does pH influence the affinity of haemoglobin?

A

In the lungs, CO2 is constantly removed. This raises the pH, which changes the shape of haemoglobin into one that loads oxygen easily and has a high affinity for it, so it isn’t released on the way to respiring tissues. In these tissues, respiring cells produce carbon dioxide. This lowers the pH and changes the shape of the haemoglobin into one that has a lower affinity for oxygen and releases it more easily. Oxygen is released into the tissues

36
Q

Why is more oxygen released from haemoglobin in cells with a fast rate of respiration?

A

More CO2 = lower pH = greater the haemoglobin shape change = more readily oxygen is unloaded

37
Q

Why do lugworms’ haemoglobin have a high affinity for oxygen?

A

Lugworms live in burrows in the sand. They get their oxygen from the fresh seawater that washes over them in the burrow. When the tide goes out, however, the concentration of oxygen in the remaining water is very low. The affinity of its haemoglobin must be very high to extract as much of this oxygen as possible

38
Q

Why does the haemoglobin of llamas have a high affinity for oxygen?

A

It lives at high altitudes where the partial pressure of oxygen is much lower. Therefore, its haemoglobin must be able to extract as much oxygen as possible

39
Q

What is important to remember about haemoglobin releasing oxygen?

A

In normal circumstances, only one oxygen molecule will be released. However, when the partial pressure of oxygen is very low, 3 molecules may be. Either way, the haemoglobin still contains some oxygen when it travels back to the lungs

40
Q

Why is a mass transport system needed?

A

Mammals have a low surface area to volume ratio, so simple diffusion isn’t effective at moving large quantities of materials over large distances

41
Q

What is the circulatory system made up of?

A

The heart and blood vessels

42
Q

What is the function of the heart?

A

It pumps blood through the blood vessels to reach different parts of the body

43
Q

What is the function of the blood?

A

Transports respiratory gases, products of digestion, metabolic waste and hormones around the body

44
Q

What are the two paths blood can take in the circulation system?

A

One loop takes blood from the heart to the lungs, then back to the heart
One loop takes blood around the rest of the body and back

45
Q

What blood vessels supply blood to the heart?

A

Coronary arteries

46
Q

Why is the transport system essential? (2)

A

It must absorb nutrients and respiratory gases and excrete products
Takes materials from cells to the exchange surface and from the exchange surface to cells

47
Q

What two factors decide whether a specialist transport system is needed?

A

The surface area to volume ratio

How active the organism is

48
Q

What four characteristics must a successful exchange system have?

A

A suitable medium in which to carry materials
A form of mass transport which is more rapid than diffusion
A closed system of tubular vessels
A mechanism for moving the transport medium between vessels

49
Q

Why are transport mediums mainly water based?

A

Water readily dissolves substances and can be moved around easily

50
Q

How is the mechanism for moving the transport medium between vessels achieved?

A

Maintaining a pressure difference

51
Q

What are the two ways in which a successful transport system is achieved?

A

Animals use a muscular contraction (can be heart or other muscles)
Plants rely on natural, passive processes like the evaporation of water

52
Q

What three important mechanisms must be present in the circulatory system?

A

A way to stop backflow (e.g. valves)
A way of controlling the flow of the medium which suits the changing needs of different body parts
A mechanism for the mass transport of gases or water

53
Q

What does the phrase ‘closed, double circulatory system’ mean?

A

The blood is confined to blood vessels and passes through the heart twice for each complete circuit of the body

54
Q

Why does blood not go directly from the lungs to the tissues that require it?

A

In the lungs, the pressure of the blood is very low. If this was to travel around the body, the rate of circulation would be too slow. Returning the blood to the heart increases its pressure and so it reaches the tissues of the body faster

55
Q

Why is it important that blood reaches the tissues that need it quickly?

A

Mammals have a high body temperature and so high metabolism

56
Q

What does the left-hand pump of the heart deal with?

A

Oxygenated blood from the lungs

57
Q

What does the right-hand side pump of the heart deal with?

A

Deoxygenated blood from the body

58
Q

What are the two chambers found in each pump?

A

The atrium and the ventricle

59
Q

Characteristics of the atrium

A

Thin-walled and elastic and stretches to collect blood

60
Q

Characteristics of the ventricle

A

Thick muscular wall to pump blood long distances

61
Q

Why is it important that the heart has two separate pumps?

A

The blood has to pass through the tiny capillaries in the lungs, which vastly reduces the pressure. This means that the flow of blood to the rest of the body would be very slow

62
Q

Why does the right ventricle have a thinner muscular wall?

A

It only pumps blood to the lungs

63
Q

Why does the left ventricle have a thicker muscular wall?

A

It pumps blood around the body

64
Q

What are the two valves found in the heart?

A

The left atrioventricular (bicuspid) valve

The right atrioventricular (tricuspid) valve

65
Q

Why do ventricles have thicker walls than the atria?

A

They have to push blood a longer distance

66
Q

What does the aorta do?

A

Connected to the left ventricle and caries oxygenated blood to all parts of the body

67
Q

What does the vena cava?

A

Connected to the right atrium bringing deoxygenated blood back from the tissue

68
Q

What does the pulmonary artery do?

A

Connected to right ventricle where the deoxygenated blood is carried to the lungs.

69
Q

What does the pulmonary vein do?

A

Connected to the left ventricle where oxygenated blood is carried back from the lungs

70
Q

How is oxygen supplied to the heart?

A

The coronary arteries

71
Q

What is myocardial infarction?

A

A heart attack

72
Q

What causes a heart attack?

A

Blockage to the coronary artery as the heart muscle is deprived of blood therefore oxygen. Causing the muscles to be unable to respire so they die

73
Q

Why is too much salt bad?

A

Raises blood pressure

74
Q

Why is too much saturated fat bad?

A

Increase low-density lipoprotein levels and blood cholesterol concentration

75
Q

Why does high blood pressure risk of heart disease?

A
  • heart has to work harder so more likely to fail
  • arteries more likely to develop aneurysm (wearing of the walls) and burst causing an haemorrhage
  • to resit the high pressure, artery walls thicken and harden, restricting the flow of blood
76
Q

How many more times are you likely to be at risk of heart disease when smoking?

A

2 to 6 times more likely

77
Q

Why does CO cause heart attaches or agina?

A

It combines easily with haemoglobin in red blood cells. Reducing the oxygen-carrying capacity. Meaning the heart has to work faster, raising blood pressure. Insufficient supply to the heart muscles during exercise.

78
Q

Why does nicotine cause thrombosis or stokes or myocardial infarction?

A

It stimulates production of hormones (adrenaline) causing heart rate and blood pressure to rise. Also causes platelets in blood to become sticky.

79
Q

What is the cardiac cycle?

A

Heart undergoes a sequence of events which are repeated

80
Q

What the two main phases of beating the heart?

A
  • systole (contracting)

* diastole (relaxing)

AQA A-Level Biology (22 decks)

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