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A-Level Biology - OCR A > 3.7 - Exchange Surfaces and Breathing > Flashcards

3.7 - Exchange Surfaces and Breathing Flashcards

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1
Q

What type of organisms tend to have very high SA:V ratios?

A

Single-celled organisms

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2
Q

How can single-celled organisms rely on diffusion via the cell membrane for gas exchange?

A
  • High SA:V ratio
  • Low metabolic rate
    Therefore exchange is efficient
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3
Q

Why can’t larger organisms rely on diffusion into cells via the cell membrane alone?

A
  • Low SA:V ratio

- High metabolic rate

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4
Q

Define surface area

A

The total area of the parts of the cell which are in contact with the environment.

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5
Q

List the factors which increase rate of diffusion

A
  • Surface area
  • Diffusion distance
  • Concentration gradient
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6
Q

What is fick’s law?

A

Rate ∝ (Concentration Gradient x SA) ÷ Diffusion Distance

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7
Q

List the gas exchange adaptations in the lungs and give examples

A

Short diffusion path

  • Alveoli walls one cell thick
  • Capillaries are close to alveolar walls
  • RBCs are pushed up against capillary walls

Large SA

  • Large numbers of alveoli
  • Vast capillary network
  • Folded surface of alveoli

Maintenance of a Steep Concentration Gradient

  • Ventilation constantly removes stale air and replenishes fresh air
  • Heart constantly circulates blood around the alveoli: removing O₂ saturated blood and introducing CO₂ to diffuse out from the blood into alveoli.

RBCs are slowed down in capillaries allowing for more time for diffusion
Hb has a high affinity for O₂ and adapts to tissue conditions
Alveoli have moist walls allowing for gases to dissolve.

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8
Q

What is the function of cartilage in the airways?

A

Cartilage provides structural support.

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9
Q

What is the function of ciliated epithelium in the airways?

A

Ciliated epithelium wafts mucous away from the lungs.

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10
Q

What is the function of goblet cells in the airways?

A

Goblet cells secrete mucous to trap dust, microorganisms etc.

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11
Q

What is the function of smooth muscle tissue in the airways?

A

Smooth muscle provides small movements such as constricting the airways.

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12
Q

What is the function of the elastic fibres in the airways?

A

Elastic fibres provide resistance - they stretch and recoil.

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13
Q

What is the function of connective tissue in the airways?

A

Connective tissue provides a structure for other structures to bind to/be supported by. It also provides protection and insulation.

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14
Q

Where is cartilage found in the airways?

A
  • Trachea
  • Bronchi
  • Bronchioles (gradually lost)
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15
Q

Where are ciliated epithelium and goblet cells found in the airways?

A
  • Trachea
  • Bronchi
  • Bronchioles
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16
Q

Where is smooth muscle found in the airways?

A
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveolar ducts
  • Alveoli (very little)
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17
Q

Where is connective tissue found in the airways?

A
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveolar ducts
  • Alveoli
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18
Q

Where are elastic fibres found in the airways?

A
  • Bronchi - smooth muscle constricts and elastic fibres widen the bronchi.
  • Alveoli - prevent over expansion and bursting. They recoil during exhalation.
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19
Q

Detail what occurs during inhalation

A
  • External intercostal muscles contract, raising ribs.
  • Diaphragm contracts (flattens)
  • Volume in chest cavity increases
  • Pressure in chest cavity decreases (below
    atmospheric pressure) and air is inhaled.
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20
Q

Detail what occurs during exhalation

A
  • External intercostal muscles relax and ribs fall
  • Diaphragm relaxes and is pushed back up
  • Volume in chest cavity decreases
  • Pressure in lungs increases (above atmospheric
    pressure) and air is exhaled.
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21
Q

Define tidal volume

A

Tidal volume - the volume of air moved in and out of the lungs at rest (0.5dm³ approx.)

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22
Q

Define vital capacity

A

The largest volume of air that can be moved in and out of the lung (5dm³ approx.)

23
Q

Define residual volume

A

The volume of air which always remains in the lungs.

24
Q

Define dead space

A

Air in the lungs that cannot be used in gas exchange (found in the airways e.g. trachea)

25
Q

Define inspiratory reserve volume

A

The extra volume of air which can be inhaled over the normal tidal volume.

26
Q

Define expiratory reserve volume

A

The extra volume of air which can be expired over the normal tidal volume.

27
Q

What two devices can measure the rate at which air can be expired from the lungs?

A
  1. Peak flow meter

2. Vitalograph

28
Q

Define total lung capacity

A

The sum of the vital capacity and residual volume.

29
Q

What is asthma?

A

A long-term, common respiratory disease caused by sensitivity of airways to allergens.

30
Q

In a spirometer, what is used to remove CO₂?

A

Soda lime is used.

31
Q

How can a spirometer be used safely?

A
  • Use medical grade O₂
  • Sterilise the mouthpiece before use
  • Be used by a fit/healthy person
32
Q

What would be seen when a person breathes out when using a spirometer?

A

The lid would rise.

33
Q

How should a spirometer be controlled during an experiment?

A
  • Use medical grade O₂
  • Have a calibrated kymograph
  • The student should wear a nose clip
34
Q

What are the problems in breathing water?

A
  • Much lower O₂ concentration
  • O₂ Concentration varies with temperature (i.e. high
    temp = low conc.)
  • Water is more viscous than air so requires more
    energy to pass across the exchange surface.
  • Air moves in and out of animals on land but water only
    moves past in one direction.
35
Q

What are gill rakers?

A

Bony/cartilage protrusions on the gill arch to prevent food particles reaching the gill filaments and obstructing gas exchange.

36
Q

What are gill filaments?

A

The organ responsible for absorbing O₂ and expelling CO₂.

They also help in slowing the water down which passes across them.

37
Q

What are gill arches?

A

A bony curved bar on either side of the throat which supports the gills. There are several gill arches on each side. Each gill arch has many gill filaments.

There is a rich blood supply within the gill arches and filaments.

38
Q

Describe inhalation in fish

A
  • Fish opens mouth and closes opercular valve
  • Increases volume of buccal cavity
  • Pressure decreases and therefore water is drawn in.
39
Q

Describe exhalation in fish

A
  • Fish closes mouth and opens opercular valve
  • Decreases volume of buccal cavity
  • Pressure increases and forces water out through the
    operculum, past the gills.
40
Q

Define afferent

A

Going into an organ (picking up O₂).

41
Q

Define efferent

A

Going out from an organ (dispatching O₂).

42
Q

What is the buccal cavity?

A

The fish’s mouth - the bottom drops and rises to increase/decrease volume.

43
Q

What is the operculum?

A

The structure which covers the gills.

44
Q

What is the opercular valve?

A

The valve which allows water out from the fish.

45
Q

What are gill lamellae?

A

Protrusions on gill filaments. They are used to increase SA of the exchange surface to maximise gas exchange efficiency.

46
Q

What is counter current flow?

A

When the blood flows in the opposite direction to the flow of water over the exchange surfaces.

47
Q

How does counter current flow maximise the efficiency of gas exchange?

A

Counter current flow maintains a steep O₂ concentration gradient between the blood and the water.
This way new O₂-poor blood is being constantly introduced to new O₂-rich water.

48
Q

List the adaptations of exchange surfaces in fish

A
  • Large SA // many gill filaments
  • Maintenance of steep concentration gradient
  • Short distances for exchange // thin exchange
    surfaces
  • Good blood supply in gill filaments
  • Overlapping gill filaments to slow water to ensure
    sufficient time for diffusion.
49
Q

What are tracheoles?

A

Branches of the tracheae which terminate in insect tissues.

50
Q

What are spiracles?

A

Holes in the abdomen and thorax of the insect which open and close to allow gas exchange to occur.

They are much like stomata and water vapour can be lost from them also.

51
Q

How are tracheae adapted for their function?

A

They have spirals of chitin along the tracheae which provide structural support, but prevent gas exchange
from happening through their walls.

52
Q

How are the tracheoles adapted for their function?

A
  • Large number of tracheoles giving a high SA for
    exchange to occur.
  • No chitin in the walls meaning gases can
    cross them freely
  • Tracheoles are moist, so gases can dissolve in
    solution, helping with gas exchange efficiency
  • Tracheoles contain tracheal fluid which reduces
    diffusion. However, in intense activity tissues
    accumulate lactic acid which lowers water potential.
    Fluid is then draw out of the tracheoles by osmosis
    which allows for more space for diffusion to occur.
53
Q

How are insects able to adjust gas exchange?

A
  • Opening and closing spiracles
  • Ventilating tracheae by muscular contraction of the
    abdomen which create pressure changes and draw
    air in.
  • Internal air sacs act as air reservoirs
  • Fluttering the spiracles waft O₂ in, whilst reducing
    water loss.
  • Holding onto CO₂ until it builds up to a high level in
    the body fluids and then opening up the spiracles and
    releasing it all at once.

A-Level Biology - OCR A (16 decks)

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