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A Level Biology > Gas Exchange > Flashcards

Gas Exchange Flashcards

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1
Q

Fish : explain how the gills allow efficient gas exchange

A

Thin lamellae provide a large surface area
Thin epithelium so short diffusion pathway
Counter current flow maintains the concentration gradient across whole length of gill
Lots of blood capillaries and thin surface of cells to speed up diffusion between water and blood

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2
Q

Fish: explain how the highly folded structures of the gill lamellae increase the efficiency of gas exchange

A

They increase the surface area over which diffusion can take place

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3
Q

Fish: describe and explain how the counter current system leads to efficient gas exchange across the gills of a fish

A

Water and blood flow in opposite directions
This maintains a concentration gradient across the whole length of the gill
As much oxygen as possible passes into the blood

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4
Q

Name the process by which carbon dioxide is removed from a single called organism

A

Diffuses out across their body surface

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5
Q

How do single celled organism absorb oxygen

A

Diffusion across their body surface

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6
Q

What do single celled organisms have that’s different to multicellular organisms

A

Large SA to volume ratio

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7
Q

Insects: explain how the tracheal system limits the size of the insect

A

The tracheal system relies on diffusion to bring oxygen to respiring tissues if insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs

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8
Q

Insects : give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects

A

Insects have spiracles that can close to reduce water loss

Insects have sunken spiracles that trap moist air

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9
Q

Explain ways in which plants limits water loss

A

Plants have a waxy cuticle which prevents the evaporation of water

Plants have hairs on their surface (lower epidermis) that trap moist air reducing water potential gradient. So less water lost by evaporation

Plants have sunken stomata which again traps moist reducing water potential gradient

The stomata can close which reduces evaporation

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10
Q

Leaves: why is there is less water lost by a plant when the air is humid

A

Humidity reduces the difference in concentration of water between the plant and air. Reduced concentration gradient= less water loss

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11
Q

What are xerophytes ?

A

Plants that are adapted to living in areas where water is in short supply

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12
Q

Give two examples of how xerophytes limit water loss

A 
Thick cuticle -
Waxy cuticle 
Rolled up leaves 
Hairy leaves 
Stomata in pits or grooves 
Reduced surface area to volume ratio 
Deep roots sunken stomata
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13
Q

Xerophytes: explain how having rolled up leaves reduces water loss

A

Traps a region of still air within the rolled leaf
The trapped region has a high water potential
No water potential gradient between the inside and outside of leaf and therefore no water loss

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14
Q

Xerophytes: explain how having hairy leaves reduces water loss

A

Traps still moist air next to the leaf surface
This reduces the water potential gradient between the inside and the outside of the leaves
Less water lost by evaporation

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15
Q

Xerophytes : explain how having stomata in pits or grooves reduces water loss

A

Trap moist air next to the leaf and reduce the water potential gradient

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16
Q

Why water is always lost from the gas exchange of terrestrial organisms ( insects and plants)

A

Gas exchange surfaces are permeable
Higher concentration of water molecules inside the animal than outside
Water will diffuse out

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17
Q

Leaves: what happens to oxygen in a plant

A

Some oxygen from photosynthesis is used in respiration

Most diffuses out of the plant

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18
Q

Plants: in the dark when photosynthesis is not occurring what is happening to oxygen and carbon dioxide

A

Oxygen diffuses into the leaf because constantly being used by cells during respiration
Carbon dioxide diffuses out of leaf because it is constantly being produced

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19
Q

How is gas exchange similar in insects and plants

A

No living cell is far from the external air and therefore is a source of oxygen and carbon dioxide

Diffusion takes place in the gas phase (air)

Both have small surface area to volume ratio

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20
Q

How are leaves adapted for rapid diffusion

A

Air spaces have a very large surface area to volume ratio

Many small pores called stomata so no cell is far from stoma so short diffusion pathway

Numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells

Large surface area of mesophyll cells for rapid diffusion

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21
Q

At times what can plants do with the gases they produce

A

The gases produced in one process can be used for the other

Photosynthesis + carbon dioxide

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22
Q

What is each stoma surrounded by

A

A pair of guard cells

23
Q

What do guard cells do ?

A

Open and close the stomata (for example when it is dark)

24
Q

Why is the stomata being able to open and close important ?

A

The stomata can close when there will be excessive water loss to minimise water loss

25
Q

Describe cross section of the leaf

A 
From bottom to top 
Guard cells 
Stomata 
Spongy mesophyll 
Palisade mesophyll 
Upper epidermis
26
Q

How does carbon dioxide in the air outside the leaf reach mesophyll cells inside the leaf

A

Carbon dioxide enters via stomata
Stomata is opened by guard cells
Diffuses through air spaces
Down concentration gradient

27
Q

What does the increase in surface area conflict with

A

Conserving water

28
Q

Why does every cell inside an insect have a short diffusion distance/ pathway

A

They are (cell) only short distance from the trachea or tracheoles

29
Q

Insects: name the tiny pores on the body surface of insects

A

Spiracles

30
Q

How much of the time are the spiracles opened and closed for

A

They are mostly closed to prevent water loss

31
Q

Insects : periodically spiracles must open why?

A

To allow for gas exchange to happen

32
Q

Insects : What is the trachea strengthened by ?

A

Rings to prevent them from collapsing

33
Q

Explain gas exchange in insects

A

Air moves into trachea through pores (spiracles)
Oxygen is used up so its conc gradient towards ends of
tracheoles falls.
Creates diffusion gradient
Oxygen travels down conc gradient
Trachea branches into tracheoles that go to individual cells
Thin permeable walls- oxygen directly to respiring cells
Co2 produced by respiring cells
Conc gradient in opposite direction
Co2 moves down conc gradient and released in atomsphere

34
Q

Why does abdominal pumping increase the efficiency of gas exchange between tracheoles and muscle tissue of insect

A

increasing the

amount of air/oxygen entering→maintains greater concentration gradient for diffusion

35
Q

removal of water from the tracheoles increases rate of diffusion of oxygen between tracheoles and muscle tissue

A

Greater surface area exposed to the air
Gases diffuse faster in air than water (more rapid)

Increases volume of air

36
Q

How does the end of the tracheoles fill up with water

A

Muscles cell around tracheoles respire
Anaerobic respiration
Lactate
Lower water potential of the muscle cells
Water from tracheoles move into cells by osmosis
Decrease volume of water in tracheoles
Further air drawn in

37
Q

Why do insects require a specialised breathing system ?

A

Insects posses an exoskeleton
This prevents gases from diffusing through
Many insects have a high metabolic rate so demand for oxygen

38
Q

How does oxygen in the tracheoles reach muscle cells

A

Air diffuses along the trachea and tracheoles
Oxygen is then dissolved in water at the end o tracheoles
Here it diffuses into the muscle cells

39
Q

The supply of oxygen to the flying muscles is affected by ?

A

Lactate
Produced by anaerobic respiration
Lowers water potential
Fluid from the tracheoles moves into the cells by osmosis
Allowing air oxygen in the tracheoles to diffuse directly into the cells
The diffusion pathway has been shortened

40
Q

Fish: What happens if blood and water flow in parallel

A

Diffusion of oxygen into the blood is less efficient
Only 50%
Equilibrium is reached as the concentration gradient cannot be maintained along the whole filament

41
Q

Xerophytes: how can reduced sa to vol ration in leaves be achieved

A

Leaves reduced to pine needles

42
Q

Lungs: what structures does the air pass through

A

Trachea- bronchi - bronchioles - alveoli

43
Q

Lungs: what prevents trachea from collapsing

A

Rings of cartridge

44
Q

Adaptions of the alveoli

A

Squamous epithelium = thin/one cell thick

  • Short diffusion pathway→fast diffusion
  • Large surface area to volume ratio - Fast diffusion
  • Permeable
  • Good blood supply from network of capillaries
  • Maintains concentration gradient
  • Elastic tissue allows it to recoil after expansion
45
Q

Why is the alveolus being one cell thick efficient for gas exchange

A

Creates a shorter diffusion pathway

46
Q

Lungs : why is the alveoli having a constant blood supply from capillaries a good thing ?

A

Steep conc gradient is constantly maintained

47
Q

Lungs : what happens to the intercostal as we breathe in

A

External intercostal contract

Internal intercostal relax

48
Q

What happens in inspiration (breathing in )

A

External intercostal muscles contract whilst the internal muscles relax
Causes the ribs to raise upwards
Diaphragm contracts and flattens
Volume inside thoracic cavity increases
Pressure decreases
Difference between pressure inside the lungs and atmospheric pressure creates gradient
Air to be forced into the lungs

49
Q

What happens expiration ?

A

Internal intercostal muscles contract
External intercostal muscles relax
Causes ribs to lower
Diaphragm muscles relax and raises upwards
Decrease volume inside the thoracic cavity
Increases pressure
Air pushed down pressure gradient

50
Q

What is vital capacity

A

The maximum volume of air that can be inhaled or exhaled in a single breath

51
Q

What is tidal volume

A

The volume of air we breathe in and out at each breath at rest

52
Q

What is the residual volume

A

Volume of air always present in the lungs

53
Q

How does oxygen in the air reach capillaries surrounding alveolus

A 
Trachea, bronchi, bronchioles
Down pressure gradient 
Down diffusion gradient 
Across alveolar epithelium 
Across capillary epithelium
54
Q

Alveoli adaptions

A

The alveoli are very thin being only around one cell thick. These are surrounded by capillaries which are also only one cell thick. This reduces the diffusion pathway for gases.

  • The constant blood supply by capillaries means that a steep concentration gradient is constantly maintained.
  • The are a large number of alveoli (~300 million), collectively giving a surface area of ~70m2.

A Level Biology (16 decks)

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