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Biology > Pack 7 - Exchange > Flashcards

Pack 7 - Exchange Flashcards

1
Q

In what two ways can substance be exchanged between the internal and external environment of an organism?

A
  • Diffusion

* Active transport

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2
Q

Why do animals with a higher metabolic rate require larger SA:V ratio?

A

They need to exchange substances at a higher rate.

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3
Q

Which has a higher SA to volume ratio - a bacterium or a mouse?

A

The bacterium

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4
Q

Why do large organisms need a specialised exchange surfaces?

A

They have a lower SA:V ratio. Substances (such as gases) need to supply and be transported to all cells. Therefore exchange surfaces increase the SA for this to take place.

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5
Q

What two ways have organisms adapted to supply all their cells with substances?

A
  • Flattened shape

* Specialised exchange surface

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6
Q

What are 5 features of specialised exchange surfaces?

A
  • Large SA
  • Thin
  • Selectively permeable
  • Movement of the external medium to maintain CG (e.g. ventilation)
  • Movement of the internal medium (e.g. blood)
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7
Q

Describe the structure of insect gas exchange systems.

A
  • Spiracles (pores)
  • Tracheae
  • Tracheoles
  • Body tissue
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8
Q

What is the importance of tracheoles in insects?

A

It means that each cell is a very short distance from a tracheal and therefore there is a short diffusion pathway for gases.

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9
Q

At rest, how does oxygen reach respiring insect cells?

A

Diffusion gradient - Oxygen diffuses along tracheoles down a concentration gradient as oxygen his used up an CO₂ diffuses out of cells.

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10
Q

How can insects increase the speed of gas exchange?

A

Mass transport - the contraction of muscles squeezes the tracheae enabling mass movement of air in and out.

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11
Q

Describe what happens to the tracheoles during periods of activity in insects and how this increases the rate of gas exchange?

A
  • Anerobic respiration
  • Lactate produced (soluble in cells)
  • Decreases the ψ of the cell.
  • Water at the ends of the tracheoles moves into the cells.
  • Draws air in.
  • Increased surface area for diffusion.
  • Diffusion is after in a gas than in liquid.
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12
Q

Why is there water at the ends of tracheoles during rest in insects? What is the payoff of this?

A
  • Decreases water loss

* It decreases the rate of diffusion of gases.

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13
Q

How can insects actively control water loss? What is the disadvantage of doing this?

A
  • Closing the spiracles

* Gases can’t diffuse in and out

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14
Q

Why would the tracheal system not work for larger organisms?

A

It relies on diffusion and therefore the diffusion pathway must be short.

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15
Q

Name the process by which CO₂ is removed from single-celled organisms.

A

Diffusion

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16
Q

Why do fish need a specialised gas exchange surface?

A

Small SA:V ratio

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17
Q

Describe the structure of a gill.

A
  • Gill filaments attached to a gill bar.

* Gill lamellae on the filaments are at right angles.

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18
Q

Which way does water flow over the gills in comparison to the direction of blood flow? What is this called?

A
  • Opposite direction

* Counter current flow

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19
Q

Describe how the countercurrent flow system means more oxygen can absorbed than with parallel flow.

A
  • Water with its highest oxygen concentration meets blood that already has a high concentration of oxygen.
  • Water with the least oxygen concentration meets blood with little oxygen.
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20
Q

What is the maximum % of the oxygen in water that could be absorbed using parallel flow?

A

50%

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21
Q

Roughly how much of the water’s oxygen can diffuse into the blood using countercurrent flow?

A

80%

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22
Q

Why does water only flow one way through a fishes gills?

A

Water is much denser than air so would require a lot of effort to flow in and out.

23
Q

How does the fish force water over its gills?

A

By decreasing the volume of its mouth and therefore increasing the pressure.

24
Q

What happens to most of the oxygen produced by photosynthesis in plants?

A

It diffuses out of the leaf (some is used for respiration)

25
Q

Do plants have a specialised gas exchange system? Why (not)?

A

No, since there is a shot fast diffusion pathway for gases in the external air to all living cells.

26
Q

Where does most gaseous exchange occur in a plant?

A

The leaves

27
Q

What three adaptation do leaves have for rapid diffusion of gases?

A
  • Stomata (no cell is far from any stomata)
  • Connected airspaces through the mesophyll.
  • Large surface area of mesophyll cells.
  • Flat - short diffusion distance to any one cell.
28
Q

Where are most stomata cells found?

A

The underside of the leaves.

29
Q

What is the name of the cells the surround the stomata?

A

Guard cells

30
Q

How is the rate of gaseous exchange controlled by plants? What conflict does this create?

A
  • Guard cells can open or close stomata.

* water loss

31
Q

How is water loss controlled by guard cells?

A

Guard cells can open or close stomata.

32
Q

In what three ways have insects evolved to reduce water loss?

A
  • Small SA:V ratio
  • Waterproof coverings
  • Spiracles can close
33
Q

What is the disadvantage of an effective gas exchange system (e.g. large surface area)?

A

Increased water loss.

34
Q

How do ALL plants reduce water loss? (Two ways)

A
  • Guard cells can open or close stomata.

* Waterproof coating

35
Q

What is a xerophyte?

A

Plants with a restricted supply of water.

36
Q

Give 5 ways in which xerophytes reduce water loss. (That other plants don’t have)

A
  • Thick cuticle
  • Rolling up leaves - traps still air with a high ψ and reduces ψ gradient.
  • Hairy leaves - traps moist air next to the leaf - reduces ψ gradient
  • Stomata in pits or grooves - trap moist still air - reduces ψ gradient
  • reduced SA:V ratio
37
Q

Why is the volume of oxygen absorbed by mammals relatively high? (2 reasons)

A
  • Large organisms

* Maintain a high body temperature and high metabolic rate

38
Q

Describe the parts of the respiratory system in order.

A
  • mouth
  • trachea
  • (lungs)
  • bronchi
  • bronchioles
  • alveoli
39
Q

How and why is the trachea supported?

A
  • Cartilage rings

* To keep it open

40
Q

What do the trachea and bronchi produces to trap dirt particles? What structure moves the particles towards the throat?

A

Mucus

Cilia

41
Q

Why are bronchiole walls made of muscle?

A

So they can restrict the flow of air

42
Q

Why do alveoli have elastic fibres?

A

To stretch when inhaling and spring back to expel CO₂ when exhaling.

43
Q

What is the process of moving air in and out of the lungs called?

A

Breathing/ventilation

44
Q

Describe how inspiration takes place. (6 steps)

A
  • External intercostal muscles contract.
  • Ribs move up and out.
  • Diaphragm contracts and flattens.
  • Thorax volume increases.
  • Pressure decreases to less than atmospheric.
  • Air moves in
45
Q

Describe how expiration takes place. (6 steps)

A
  • Internal intercostal muscles contract.
  • Ribs move down and in.
  • Diaphragm relaxes and flattens.
  • Thorax volume decreases.
  • Pressure increases to more than atmospheric.
  • Air moves out
46
Q

State an equation for pulmonary ventilation. (give units)

A

pulmonary ventilation (dm³min⁻ⁱ) = tidal volume (dm³) x breathing rate (min⁻ⁱ)

47
Q

What is tidal volume?

A

The volume of air normally breathed in in one breath.

48
Q

Where is the site of gas exchange in mammals?

A

The epithelial cells of the alveoli.

49
Q

Describe the structure of alveoli epithelial cells.

A

Flat

50
Q

How many cells thick is the wall of an alveolus

A

1

51
Q

Describe the movement of an oxygen molecule from the alveoli air sac to the red blood cell.

A
  • The epithelial cells of the alveoli.
  • The endothelial cells of the capillaries.
  • Blood plasma
  • Red blood cell
52
Q

What is the advantage of having red blood cells be squeezed through the small capillaries? (2)

A
  • Slows their movement - more time for diffusion

* Shorter diffusion distance

53
Q

How is a concentration gradient maintained in the human gas exchange?

A
  • Movement of blood

* Movement of air - ventilation

Biology (18 decks)

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