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12E Year 12 Biology > 3.3.2 Gas Exchange > Flashcards

3.3.2 Gas Exchange Flashcards

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
What are hydrophytes?
Plants adapted to a freshwater habitat
26
Why have xerophytes adapted to have a thick cuticle?
Waxy surface on leaves forms a waterproof barrier | The thicker the cuticle, the less water is lost
27
Why have xerophytes adapted to have a small surface area?
Smaller rate of diffusion Leaves are small and circular Rate of water loss is reduced Balanced against area for photosynthesis
28
Why have xerophytes adapted to have a low stomata density?
Because there is a smaller surface area for diffusion
29
Why have xerophytes adapted to have sunken stomata?
They trap still, moist air and reduce the water potential gradient
30
Why have xerophytes adapted to have stomatal hairs?
Especially on the lower epidermis Traps still, moist air Water potential gradient is reduced so that less water is lost via evaporation
31
Why have xerophytes adapted to have the rolling of leaves?
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
Why have xerophytes adapted to have extensive roots?
Collects water from a wide region | Increases water collected
33
Why have xerophytes adapted to have a low water potential inside leaf cells?
Water moves in via osmosis | This maximises water uptake
34
What is pulmonary ventilation rate?
The total volume of air that is moved into the lungs during one minute
35
What is the equation for pulmonary ventilation?
Tidal volume (dm3) X breathing rate (min~1)
36
What is tidal volume?
The volume of air normally taken in at each breath when the body is at rest. This is usually around 0.5dm3
37
What is ventilation rate?
The number of breaths taken in 1 minute
38
What does a peak flow metre do?
It measures the peak expiratory flow rate to check if the airway is blocked
39
What is the FEV?
Force expiratory value | The maximum amount of air that can be forced out in 1 second
40
What is a spirometer?
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
What is the resting tidal volume?
The volume breathed in/out at rest
42
What is vital capacity?
The maximum volume that can be breathed in/out
43
Why is there a large amount of gas exchange in humans?
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
Why are the lungs inside the body?
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
What is the ribcage?
A cage on bones which protect the lungs
46
What are the lungs?
A pair of lobed structures in which gas exchange occurs
47
What is the trachea?
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
What are the bronchi?
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
What are bronchioles?
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
What are alveoli?
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
What is ventilation?
Breathing | The constant movement of air in/out of the lungs
52
What are the steps for inspiration?
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
What are the steps for expiration?
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
What are internal intercostal muscles?
The muscles surrounding the lung | Their contraction leads to expiration
55
What are external intercostal muscles?
The muscles connecting the ribs | Their contraction leads to inspiration
56
How is the breathing system kept seperate from the rest of the body?
By the diaphragm
57
How does oxygen diffuse into the blood?
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
Why is the diffusion of gases between the alveoli and the blood very rapid?
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
Why is tobacco harmful?
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
What are the three types of muscles in the human gas exchange system?
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
What is the structure of the human gas exchange system? (No explanation)
``` Rib cage Lungs Trachea Bronchi Bronchioles Alveoli ```

12E Year 12 Biology (17 decks)

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