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Grice/Grace AQA A-Level Biology Revision Year 12 > 3.3.2 Gas Exchange > Flashcards

3.3.2 Gas Exchange Flashcards

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1
Q

What are the characteristics of single-celled organisms and insects?

A

Small so therefore have a large surface area to volume ratio

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2
Q

What is the internal system of insects?

A

Internal network of tubes called tracheae
Tracheae are supported by strengthened rings which prevent them from collapsing
Tracheae divide into smaller dead-end tubes called tracheoles
Tracheoles extend throughout the bodily tissues
This creates a short diffusion pathway

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3
Q

How do respiratory gases move in/out of the trachea via the diffusion gradient?

A

When cells are respiring, oxygen is used up and the concentration at the ends of the tracheoles falls
The concentration gradient causes oxygen to diffuse from the air to the tracheae to cells
Carbon dioxide is produced by cells which creates an opposite concentration gradient
Carbon dioxide diffuse from the cell’s to the atmosphere
Diffusion in air is more rapid than in water so this is a quick method

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4
Q

How do respiratory gases move in/out of the trachea via mass transport?

A

The contraction of muscles in insects can squeeze the tracheae enabling mass movements of air in and out
This spread up the exchange of respiratory gases

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5
Q

How do respiratory gases move in and out of the trachea system via the ends of the tracheoles being filled with water?

A

During major activity, the muscle cells around the tracheoles respire anaerobically
This produces lactate which is soluble and lowers water potential
Water moves into the cells from the tracheoles by osmosis
The water decreases in volume and so draws air into them
The final diffusion pathway is in a gas rather than a liquid phase so is more rapid
This leads to greater water evaporation

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6
Q

How do gases enter/leave the trachea?

A

Through tiny pores called spiracles on the body surface
Opened and closed by a valve
Mostly kept closed to reduce water loss

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7
Q

How are spiracles opened/closed?

A

Via valves

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8
Q

What are the problems associated with spiracles?

A

When they are open, they cause water loss

They’re usually closed to stop this problem

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9
Q

Why are insects small?

A

The tracheal system relies mostly on diffusion

The diffusion pathway must be short which is why insects are small

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10
Q

What is the outer coating of a fish?

A

Waterproof

Gas-tight outer coating

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11
Q

Where are gills found?

A

In fish, behind the head

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12
Q

What is the structure of gills?

A

Gills are made of gill filaments

Gill lamellae are at right angles to the gill filaments which increase the surface area of the gills

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13
Q

How does water get to the gills?

A

Water is taken in through the mouth then forced over the gills and out through an opening in each side of the body

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14
Q

What is a countercurrent flow?

A

When water flows opposite to the blood

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15
Q

What is the oxygen content of water?

How does this affect fish?

A

1%

Therefore they need to take in a lot of water

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16
Q

How does the countercurrent help diffusion of oxygen?

A

Blood that is already loaded with oxygen meets with water that’s loaded with oxygen
Blood with little oxygen meets water with little oxygen
This means diffusion of oxygen from water to blood is constantly taking place

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17
Q

How does photosynthesis and respiration benefit eachother?

A

The products of photosynthesis supplies the reactants of respiration and vice versa
Most CO2 is gained from external air

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18
Q

What happens to a plant when photosynthesis doesn’t occur (in the dark)?

A

Respiration occurs more rapidly

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19
Q

How are leaves adapted for photosynthesis/respiration?

A

Large surface area: rapid diffusion
Thin and flat leaves: short diffusion pathway
Stomata usually occur on the underside of the leaf: stops water loss
Numerous interconnecting air spaces: allow for gases to come in contact with mesophyll cells
Guard cells: open and close stoma to prevent water loss

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20
Q

How do plants differ in air and water? Why?

A

Diffusion takes place in air which makes it more rapid than in water

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21
Q

What are stomata? What do they do?

A

They are pores in the under surface of the leaf

They allow for a short diffusion pathway

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22
Q

What are mesophytes?

A

Plants adapted to a habitat with adequate water

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23
Q

What is a xerophyte?

A

Plants adapted to a dry habitat

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24
Q

What are halophytes?

A

Plants adapted to a salty habitat

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25
Q

What are hydrophytes?

A

Plants adapted to a freshwater habitat

26
Q

Why have xerophytes adapted to have a thick cuticle?

A

Waxy surface on leaves forms a waterproof barrier

The thicker the cuticle, the less water is lost

27
Q

Why have xerophytes adapted to have a small surface area?

A

Smaller rate of diffusion
Leaves are small and circular
Rate of water loss is reduced
Balanced against area for photosynthesis

28
Q

Why have xerophytes adapted to have a low stomata density?

A

Because there is a smaller surface area for diffusion

29
Q

Why have xerophytes adapted to have sunken stomata?

A

They trap still, moist air and reduce the water potential gradient

30
Q

Why have xerophytes adapted to have stomatal hairs?

A

Especially on the lower epidermis
Traps still, moist air
Water potential gradient is reduced so that less water is lost via evaporation

31
Q

Why have xerophytes adapted to have the rolling of leaves?

A

Protects lower epidermis from the outside traps a region of still air
Region has a high water potential- water vapour
There is no water gradient so there is no water loss

32
Q

Why have xerophytes adapted to have extensive roots?

A

Collects water from a wide region

Increases water collected

33
Q

Why have xerophytes adapted to have a low water potential inside leaf cells?

A

Water moves in via osmosis

This maximises water uptake

34
Q

What is pulmonary ventilation rate?

A

The total volume of air that is moved into the lungs during one minute

35
Q

What is the equation for pulmonary ventilation?

A

Tidal volume (dm3) X breathing rate (min~1)

36
Q

What is tidal volume?

A

The volume of air normally taken in at each breath when the body is at rest. This is usually around 0.5dm3

37
Q

What is ventilation rate?

A

The number of breaths taken in 1 minute

38
Q

What does a peak flow metre do?

A

It measures the peak expiratory flow rate to check if the airway is blocked

39
Q

What is the FEV?

A

Force expiratory value

The maximum amount of air that can be forced out in 1 second

40
Q

What is a spirometer?

A

It consists of a chamber filled with oxygen that floats on water
A person breathes from the tube which makes it sink
Breathing in makes it float
The movements are recorded to work out FEV

41
Q

What is the resting tidal volume?

A

The volume breathed in/out at rest

42
Q

What is vital capacity?

A

The maximum volume that can be breathed in/out

43
Q

Why is there a large amount of gas exchange in humans?

A

They are large organisms with a large amount of cells

They maintain a high body temperature which is related to them having high metabolic and respiratory rates

44
Q

Why are the lungs inside the body?

A

Because air is not dense enough to protect these delicate organs from structures and the body would otherwise lose a lot of water and dry out

45
Q

What is the ribcage?

A

A cage on bones which protect the lungs

46
Q

What are the lungs?

A

A pair of lobed structures in which gas exchange occurs

47
Q

What is the trachea?

A

A flexible airway
Supported by rings of cartilage
Cartilage prevents the trachea from collapsing as the air pressure inside falls when breathing in
Tracheal walls are made of muscle
Lined with ciliated epithelium and goblet cells

48
Q

What are the bronchi?

A

Two divisions of the trachea, leading to one lung
They produce mucus to trap dirt particles and have cilia which move mucus up into the throat
Larger bronchi have supportive cartilage
Amount of cartilage reduces as bronchi get smaller

49
Q

What are bronchioles?

A

A series of branching subdivisions of the bronchi
Their walls are made of muscle lined with epithelial cells
The muscle allows them to constrict so that they can control air flow in/out of the alveoli

50
Q

What are alveoli?

A

Minute air sacs at the end of the bronchioles
Between the alveoli there are some collagen and elastic fibres
The alveoli are lined with epithlium
The elastic fibres allow them to stretch as they fill with air, they they spring back in order to expel the CO2 rich air

51
Q

What is ventilation?

A

Breathing

The constant movement of air in/out of the lungs

52
Q

What are the steps for inspiration?

A

External intercostal muscles contract
Internal intercostal muscles relax
Ribs are pulled upwards and outwards, increasing thorax volume
Diaphragm muscles contract, causing it to flatten, which increases the thorax volume
Increased volume of the thorax results in reduction of pressure in the lungs
Atmospheric pressure is greater than pulmonary pressure and so air is forced into the lungs

53
Q

What are the steps for expiration?

A

Internal intercostal muscles contract
External intercostal muscles relax
Ribs move downwards and inwards to decrease the thorax volume
Diaphragm muscles relax and so is pushed up by the previously compressed contents of the abdomen
Volume of the thorax is further decreased
Decreased volume increases the pressure in the lungs
The pulmonary pressure is now greater than in the atmosphere so air is forced out of the lungs

54
Q

What are internal intercostal muscles?

A

The muscles surrounding the lung

Their contraction leads to expiration

55
Q

What are external intercostal muscles?

A

The muscles connecting the ribs

Their contraction leads to inspiration

56
Q

How is the breathing system kept seperate from the rest of the body?

A

By the diaphragm

57
Q

How does oxygen diffuse into the blood?

A

Around each alveolus is a network of pulmonary capillaries so narrow that red blood cells are flattened against the thin capillary walls in order to squeeze through

58
Q

Why is the diffusion of gases between the alveoli and the blood very rapid?

A

Red blood cells are slowed when passing through capillaries which allows more time for diffusion
The distance between the alveolar air and red blood cells is reduced as the red blood cells are flattened against the capillary walls
Alveoli/capillary walls are short so diffusion distance is short
Alveoli and pulmonary capillaries have a very large surface area
Breathing constantly ventilates the lungs and the heat pushes blood through the capillaries so that a steep concentration gradient is achieved

59
Q

Why is tobacco harmful?

A

Many tobacco products are toxic to cilia which reduces the number of cilia and stop them from fully functioning
It causes emphysema, bronchitis, cancer, heart disease

60
Q

What are the three types of muscles in the human gas exchange system?

A

Diaphragm: sheet of muscle which that separates the thorax from the abdomen
Intercostal muscles:
Internal intercostal muscles: whose contraction leads to expiration
External intercostal muscles: whose contraction leads to inspiration

61
Q

What is the structure of the human gas exchange system? (No explanation)

A 
Rib cage
Lungs
Trachea
Bronchi
Bronchioles
Alveoli

Grice/Grace AQA A-Level Biology Revision Year 12 (60 decks)

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