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A Level Biology OCR A UPDATED > 7 - Exchange Surfaces > Flashcards

7 - Exchange Surfaces Flashcards

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1
Q

Why can’t fish breathe in and out via ventilation?

A

Water is denser, more viscous and has a lower oxygen content than air, so requires too much energy to be efficiently moved by a 2-way ventilation system

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2
Q

Do prokaryotes need specialised exchange surfaces?

A

No as they are small enough to get the resources they need via osmosis, diffusion etc.

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3
Q

Why do larger, eukaryotic organisms need specialised exchange surfaces?

A

Because they have greater metabolisms so need more resources and have lower SA:V ratios so cannot get all of these resources via simple diffusion, osmosis etc. as the substances need to travel further to get to our internal cells

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4
Q

What are 4 things all good exchange surfaces should have/be?

A
  1. Large surface area 2. Thin 3. Good ventilation 4. Good blood supply
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5
Q

How does having a large surface area aid exchange surfaces?

A

Allows more substances to travel across at a time, increasing exchange rate

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6
Q

How does being thin aid exchange surfaces?

A

Allows substances to travel across them more quickly, increasing exchange rate

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7
Q

How does having a good blood supply aid exchange surfaces?

A

Allows optimal concentration gradient to be maintained by bringing/taking away substances quickly

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8
Q

How does having good ventilation aid exchange surfaces?

A

Allows a steep concentration gradient to be maintained

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9
Q

Why can a single-celled organism only reach a certain size?

A

Because any larger and it’s SA:V ratio would be too small for it to support its metabolism when only transporting materials via diffusion, osmosis etc.

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10
Q

What is an exotherm?

A

A cold-blooded organism

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11
Q

What is an endotherm?

A

A warm-blooded animal

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12
Q

Why do mammals need excellent exchange surfaces?

A

Because they have large metabolisms

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13
Q

What is the exchange surface area of the lungs?

A

Around 55-57 metres squared

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14
Q

What is the biological name for the mouth?

A

The buccal cavity

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15
Q

What is the purpose of the nasal cavity?

A

Increases the temperature and moisture content of inhaled air. It’s hairy, mucus-secreting lining also traps pathogens and irritants

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16
Q

What is the membrane on the surface of the lungs called?

A

Pleural Membrane

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17
Q

What are the muscles between the ribs called?

A

Intercostal muscles

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18
Q

What is the sequence of airways that air passes down?

A

Mouth/Nostril—>Buccal/nasal cavity—>Trachea—>Bronchus—>Bronchioles—>Alveoli

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19
Q

Which bones protect the chest cavity?

A

The ribs

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20
Q

Why does the trachea have c-shaped rings of cartilage?

A

To prevent it from collapsing due to pressure changes in the lungs

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21
Q

What two types of cells is the trachea lined by?

A

Goblet and Ciliated Epithelial cells

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22
Q

What is the purpose of goblet cells?

A

They secrete mucus, which traps dust and microbes

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23
Q

What is the purpose of ciliated epithelial cells?

A

They are adjoining to goblet cells, and use their cilia to sweep mucus and whatever is trapped within it out into the throat

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24
Q

What is the structure of the bronchi and trachea?

A

bronchi are
narrower than trachea. They are composed of several layers which together make up a thick wall. The
wall is mostly composed of cartilage, in the form of incomplete C rings (bronchi have trachea but do not form c-rings but can form full rings and irregular blocks). Inside surface of
the cartilage is a layer of glandular and connective tissue, elastic fibres, smooth muscle
and blood vessels. This is referred to as the ‘loose tissue’. The inner lining is an epithelial
layer composed of ciliated epithelium and goblet cells.

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25
Q

Which bronchioles have cartilage?

A

Those with a diameter greater than 1mm

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26
Q

What is the purpose of smooth muscle cells contained in the walls of the bronchioles?

A

To allow them to dilate and constrict

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27
Q

Are ciliated cells present in the bronchioles and alveoli?

A

No

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28
Q

Is gas exchange possible in the bronchioles?

A

Some, through the flattened epithelial lining

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29
Q

What is the diameter of alveoli?

A

200-300 micrometers

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30
Q

What are the walls of alveoli made up of?

A

Squamous epithelial cells, some collagen and elastic fibres made from elastin

31
Q

What is the purpose of the elastic tissues in alveoli?

A

They allow the alveoli to stretch when air enters, and recoil in order to help force air out

32
Q

Where is lung surfactant found?

A

Coating the inside of alveoli

33
Q

What are the 2 purposes of lung surfactant?

A

Prevent the alveoli from collapsing and help prevent water loss

34
Q

What is the purpose of external intercostal muscles?

A

When they contract, they lift the ribcage up and out (during inhalation)

35
Q

What is the purpose of internal intercostal muscles?

A

They push the ribcage downwards and inwards during forced exhalation

36
Q

What 2 steps occur during inspiration?

A
  1. Intercostals contract, making ribcage move upwards and outwards 2. Around the same time, diaphragm contracts and flattens
37
Q

What effect does the movements of the diaphragm and intercostal muscles have during inspiration?

A

Increases the volume of the chest cavity, causing its pressure to become lower than atmospheric pressure, meaning air moves into the lungs

38
Q

What 2 steps occur during expiration?

A
  1. The intercostal muscles relax, making the ribcage move downwards and inwards 2. The diaphragm relaxes and expands into a dome shape
39
Q

What effect does the movements of the diaphragm and intercostal muscles have during expiration?

A

They decrease the volume of the chest cavity, causing its pressure to increase to more than atmospheric pressure and, with the help of the recoil of the elastic fibres in the alveoli, forcing air out of the lungs

40
Q

What are 3 methods of measuring the volume of gas drawn into the lungs?

A
  1. A peak flow meter 2. A vitalograph 3. A spirometer
41
Q

What is a peak flow meter?

A

A plastic tube with an analog measuring device to record peak flow rate, which you blow into. Sharp exhalation needed.

42
Q

What is a vitalograph?

A

Essentially the same thing as a peak flow meter but with a digital data logger which produces a graph of force over time as well as ‘forced expiratory volume in 1 second’

43
Q

How does a spirometer work?

A

It is a lid bobbing on a tank of water. A person puts in a mouthpiece (whilst wearing a nose clip) attached to a tube which leads into the water. Their breathing thus causes the lid to bob up and down, and it is attached to a pen which creates a trace on a revolving drum of paper

44
Q

Why does a spirometer have a canister of soda lime?

A

To filter the CO2 from the user’s limited air supply so that they don’t suffer CO2 poisoning

45
Q

Why does a person using a spirometer wear a nose clip?

A

To ensure that the flow of air occurs only through their mouth, thus allowing for accurate readings

46
Q

What is tidal volume?

A

The amount of air which moves into and out of the lungs with each resting breath

47
Q

How much is the typical tidal volume for an adult?

A

~500cm^3, or around 15% of vital capacity

48
Q

What is vital capacity?

A

The amount of air that can be breathed in when the strongest possible exhalation is followed by the strongest possible inhalation

49
Q

What is the inspiratory reserve volume?

A

The amount of air you can breathe in over and above a normal inhalation (after normal tidal volume)

50
Q

What is expiratory reserve volume?

A

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

51
Q

What is residual volume?

A

The volume of air left in your lungs when you have exhaled as hard as possible

52
Q

Can residual volume be measured directly?

A

No

53
Q

What is total lung capacity?

A

Vital capacity plus residual volume

54
Q

What is inspiratory capacity?

A

Total volume of air taken in by deepest possible inhalation following normal exhalation

55
Q

Why can’t fish breathe in and out by ventilation?

A

Because water is much denser and more viscous than air, and has a much lower oxygen content, so it saves energy for them to move water in 1 direction only

56
Q

Why do fish gills have a vivid red colour?

A

Because they contain many capillaries

57
Q

What happens when a fish opens its mouth?

A

The operculum closes over the gills, the buccal cavity expands and the opercular valve (to the outside) is closed. This means that the pressure in the mouth drops, and water rushes in

58
Q

What happens when a fish closes its mouth?

A

Afterwards, fish closes its mouth, causing the buccal cavity
floor to raise, thus increasing the pressure. The water is forced over the gill filaments by the
difference in pressure between the mouth cavity and opercular cavity. The operculum
acts as a valve and pump and lets water out and pumps it in.

59
Q

Why can’t fish breathe in air?

A

Without water the gill structures collapse, meaning that their exchange surface area is not large enough to keep the fish alive.The projections (gill filaments) are held apart by water flow. Therefore, in the absence of water they stick
together, thus meaning fish cannot survive very long out of water.

60
Q

What are the purposes of a fish’s lamallae?

A
  1. To direct the flow of water in the gills
  2. increase surface area
61
Q

What is the general structure of the gills in terms of gill arches, gill filaments and lamellae?

A

Bony fish have four pairs of gills, each gill supported by an
arch.Cylindrical gill arch with arteries (containing deoxygenated blood) and vessels (taking oxygenated blood from the gills. These have 2 rows of gill filaments off them, which are have lamellae crossing them to increase surface area

62
Q

What, briefly, is the counter-current flow system and why is it used by fish?

A

It is where fish have blood flowing one way and water flowing the other. This is so that the concentration gradient of CO2 and oxygen is maintained throughout the gill, thus maximising the efficiency of diffusion

63
Q

What is a spiracle?

A

A small opening in the exoskeleton of an insect’s abdomen and thorax, which it uses to exchange gases with the atmosphere

64
Q

What is a spiracle sphincter?

A

The things which an insect uses to open and close its spiracles, allowing it to close them when oxygen demands are low to reduce water loss

65
Q

What are trachea (in insects)?

A

Small tubes (<1mm) which lead away from spiracles.

66
Q

How are insect spiracles kept open?

A

By spirals of the tough polysaccharide chitin

67
Q

What diameter are insect tracheoles?

A

0.6-0.8 micrometers

68
Q

What are insect tracheoles?

A

Smaller tubes which branch off from the trachea and run in between individual cells to give a very large surface area

69
Q

Do tracheoles have chitin?

A

No, in order to maximise gas permeability

70
Q

What is tracheal fluid?

A

Fluid found near the end of tracheoles. Gases can dissolve into it and then diffuse across to cells. However, it can also move out of the tracheoles by diffusion if necessary by osmosis (usually due to lactic acid buildup) to expose a greater surface area in them for diffusion to occur across.

71
Q

Apart from counter-current flow system, what is another adaption in fish which helps maximise gas exchange effectiveness?

A

The tips of their gill filaments overlap, increasing the resistance to the flow of water and slowing down water movement, helping maximise the time that diffusion can occur for

72
Q

What 2 adaptations do insects with high energy demands have to maximise gas exchange?

A
  1. Some can actively pump air in and out of their body by moving their thorax and/or abdomen 2. Some have internal air sacs which can be inflated and deflated by movement of the thorax and abdomen in order to increase the volume of air which moves
73
Q

What are insect tracheoles?

A

Smaller tubes (0.4-0.6 micrometers in diameter) which branch off from trachea and run in between individual cells

A Level Biology OCR A UPDATED (25 decks)

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