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Bio Component 3 > Gas Exchange > Flashcards

Gas Exchange Flashcards

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1
Q

Define gas exchange

A

Process by which oxygen reaches cells and carbon dioxide is removed from them

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2
Q

Define ventilation

A

The process of moving the respiratory medium over the respiratory surface to maintain a concentration gradient, replacing stale air high in CO2 with fresh oxygenated air

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3
Q

Define respiration

A

Series of chemical reactions that result in the release of energy in the form of ATP

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4
Q

Features of gas exchange in unicellular organisms eg amoeba (aquatic)

A
  • extremely large SA:V ratio
  • gas exchange occurs across whole surface
  • permeable membrane allows diffusion of gases
  • specialised gas exchange organs are not required
  • diffusion is sufficient enough to meet the oxygen requirements of the organism
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5
Q

Features of gas exchange in simple multicellular organisms eg flatworm (aquatic)

A
  • these organisms have evolved a flattened shape to overcome the problem of an increase in size
  • this increases their SA:V so no cell in the body if far from the surface (short diffusion pathway) - no need for specialised gas exchange organs
  • They exchange gases directly with environment via diffusion - diffusion across permeable membrane is sufficient to meet oxygen demands of organism
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6
Q

Features of gas exchange in simple multicellular organisms eg earthworm (terrestrial)

A
  • tubular shape
  • restricted to damp environments
  • worms secrete mucus to keep the cells of the body surface moist
  • elongated shape provides large SA:V
  • exchange gases directly with environment by diffusion
  • blood vessels are close to body surface so gases can diffuse in/out of blood then across the cells covering the body surface
  • blood circulated in the vessels maintaining concentration gradient for O2 in and CO2 out
  • blood contains respiratory pigment haemoglobin
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7
Q

Why do multicellular organisms require a specialised gas exchange surface?

A
  • As size of organism increases, SA:V decreases
  • Diffusion across body surface doesn’t provide sufficient oxygen
  • Larger organisms are more metabolically active so higher oxygen demand
  • Diffusion pathway across body surface is too large and rate of diffusion is too slow
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8
Q

What are the 3 gas exchange surfaces?

A
  • Gill lamellae (fish)
  • Alveoli (mammals)
  • End of tracheoles (insects)
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9
Q

To achieve the maximum rate of diffusion, what must all respiratory surfaces be?

A
  • Large surface area for diffusion of oxygen and carbon dioxide
  • Thin - shorter diffusion pathway
  • Moist - gasses dissolve and diffuse
  • Permeable to gases
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10
Q

What additional feature increases the efficiency of gas exchange in organisms which possess a circulatory system and respiratory pigment?

A
  • Extensive blood supply and blood circulates to maintain a diffusion gradient
  • Respiratory pigment such as haemoglobin which increases the oxygen carrying capacity in the blood
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11
Q

How does air diffuse into the insect?

A

Through spiracles which lead to a system of branched chitin lines air tubes called tracheae

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12
Q

Why is it important that spiracles open and close?

A

When open they allow for the diffusion of oxygen in and carbon dioxide out
When closed, water evaporation is reduced

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13
Q

How are the tracheae ventilated?

A

Movements of the abdomen

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14
Q

What is the surface of the tracheoles lined with and why?

A

A spiral fold of chitin. This keeps the airways open during body movements while allowing some flexibility

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15
Q

Ends of the tracheoles are fluid-filled. How does the fluid help to improve the efficiency of gas exchange?

A

Oxygen dissolves in the fluid and when muscles contract, this fluid (with oxygen) is drawn into the muscle cells

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16
Q

What are the advantages of the trachaeal system for gas exchange?

A
  • Oxygen is supplied directly to tissues
  • No respiratory pigment is needed
  • Oxygen diffuses faster in air than in blood
  • Spiracles close to reduce water loss
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17
Q

What is the disadvantage of the insect tracheal system?

A

Insect size/shape is limited - diffusion distance too long. Chitin needed would be too heavy.

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18
Q

Why are the gas exchange organs retained inside the body of all terrestrial organisms?

A
  • Reduces water loss
  • Reduces heat loss
  • Protection by the ribs or exoskeleton
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19
Q

What problems are caused by living in water?

A
  • Water contains less oxygen than air
  • Rate of diffusion is slower in water
  • Water is a dense medium so it doesn’t flow as freely as air
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20
Q

What is the skeleton of cartilaginous fish made of?

A

Cartilage

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21
Q

What kind of water do nearly all cartilaginous fish live in?

A

Sea water

22
Q

How many gill clefts do cartilaginous fish have?

A

5 on each side

23
Q

What kind of flow do cartilaginous fish use?

A

Parallel

24
Q

What is the internal skeleton of bony fish made of?

A

Bone

25
Q

Gills of bony fish are covered with a flap called?

A

The operculum

26
Q

What kind of flow do bony fish use?

A

Counter-current flow

27
Q

Describe the ventilation mechanism in fish

A

Water flows in:
Mouth opens and floor of buccal cavity lowers increasing volume, decreasing pressure so water drawn in through mouth. Operculum is closed.
Water flows out:
Mouth closes and floor of buccal cavity rises decreasing volume and increasing pressure so water flows out through the operculum.

28
Q

Describe counter current flow (bony fish)

A
  • Water flows between gill lamellae in the opposite direction to blood flow
  • Blood always meets water with a higher oxygen concentration
  • The gradient for diffusion of oxygen into the blood from the water is maintained over the whole length of the gill lamellae so oxygen diffuses into blood across whole length of gill lamellae
  • Counter current flow is more efficient than parallel flow as it results in a higher blood oxygen saturation level
29
Q

Describe parallel flow (cartilaginous fish)

A
  • Water is taken into the mouth and blood flows through the capillaries in the same direction as the water
  • Gas exchange is very efficient at first as there is a very steep concentration gradient
  • About halfway along the gill lamellae, equilibrium is reached so diffusion of oxygen and carbon dioxide is no longer possible
30
Q

EQ: Locusts are large insects. Explain how they ensure an efficient supply of oxygen to their tissues (2)

A
  • Tracheal system/tracheoles
  • Oxygen delivered directly to tissues
31
Q

What’s the difference between gas exchange in adult amphibians (eg frog) when inactive and when active?

A

When inactive - diffusion across their moist surface
When active - lungs

32
Q

Describe the lung structure of an amphibian

A

Lungs have a simple structure with little unfolding of the gas exchange tissues

33
Q

Rings of cartilage support the trachea, bronchi and bronchioles. Suggest a reason for this cartilage

A

To prevent the airways from collapsing during inspiration when the pressure is low.
To allow flexibility around oesophagus when eating

34
Q

What is the name of the airtight compartment of the body that encloses the lungs?

A

Thorax

35
Q

Where are goblet cells found?

A

Trachea

36
Q

What is the function of the ciliated epithelium containing goblet cells lining the trachea?

A

Cilia on surface waft mucus up and out of the trachea to avoid infection
Goblet cells produce and secrete mucus to trap microorganisms.

37
Q

What effect does emphysema have on lung tissue?

A

Breaks down alveoli air sac walls, drastically reducing the gas exchange surface area

38
Q

Describe inspiration

A
  • External intercostal muscles contract raising the ribs up and out
  • The outer pleural membrane is pulled outwards, reducing the pressure in the pleural cavity
  • The inner pleural membrane is pulled outwards causing an increase in lung volume
  • Lung surface is drawn out, causing the alveoli to expand
  • The pressure in the alveoli is lover than atmospheric pressure so air moves in
39
Q

Describe expiration

A
  • The external intercostal muscles relax, moving the ribs down and in
  • The outer pleural membrane moves inwards
  • The inner pleural membrane moves inwards
  • Lungs move in and alveoli deflate
  • The pressure in the alveoli is higher than atmospheric so air moves out
40
Q

Why are alveoli a suitable gas exchange surface?

A
  • Small and many of them - large surface area for diffusion of gases
  • Alveoli are 1 cell thick, capillary walls are also 1 cell thick - short diffusion distance
  • Each alveolus has an extensive capillary network - the circulation of blood maintains a concentration gradient of O2 and CO2
  • Moist surfactant - gases dissolve and diffuse more easily
41
Q

Why is the cellular demand for oxygen higher in a mammal compared to a fish of the same size?

A

Mammals have a higher body temperature than the fish. Mammals have a higher metabolic rate to maintain body temperature as heat is a byproduct of aerobic respiration

42
Q

Name 4 adaptations of leaves to gas exchange

A
  • The lead blade is thin and has a large surface area
  • The spongy mesophyll is permeated with air spaces to allow diffusion and circulation of gases which maintains diffusion gradients
  • The stomatal pores open to allow gas exchange to occur and reduce water loss so surfaces are kept moist
  • Mesophyll cells have partially permeable membranes to allow diffusion of gases
43
Q

Name 7 adaptations of leaves for photosynthesis

A
  • Large surface area - absorb as much light as possible
  • Leaves can orientate themselves towards the sunlight
  • Leaves are thin to allow light to penetrate lower layers
  • Cuticle and epidermis are transparent to allow light to pass to the mesophyll below
  • Palisade cells are elongated and densely packed and contain many chloroplasts
  • Chloroplasts can rotate and move within the mesophyll cells to maximise light absorption
  • Intercellular air space allow CO2 to diffuse into cells, oxygen and water vapour to diffuse away
44
Q

Where in the leaf are stomata found?

A

Lower epidermis

45
Q

What is the role of the stomata?

A

Gas exchange occurs between the external atmosphere and internal tissues of the leaf through stomata

46
Q

What is unusual about guard cells?

A
  • They are the only epidermal cells that contain chloroplasts
  • They have unevenly thickened cell walls
47
Q

Describe the mechanism for stomatal opening

A
  • Potassium ions (K+) are actively transported from the epidermal cells into the guard cells
  • Stored starch (insoluble) in the guard cells is converted into soluble malate by enzymes in the cytoplasm
  • The water potential is lowered so water enters by osmosis
  • The guard cells become turgid and curve apart because the outer cell walls are thinner than the inner cell walls
48
Q

Why are stomata usually open during the day?

A

To allow CO2 to diffuse into the leaf for photosynthesis. (Also O2 produced by photosynthesis and water vapour can diffuse out)

49
Q

Why are stomata closed at night?

A

To reduce water loss

50
Q

Explain 4 ways in which the gills of bony fish are adapted for gas exchange

A
  1. Very thin so short diffusion distance
  2. Large blood supply maintaining a steep concentration gradient of oxygen in and carbon dioxide out
  3. Many gill lamellae provides a large surface area for diffusion
  4. Counter current flow maintains a concentration gradient across the whole length of the gill lamellae

Bio Component 3 (8 decks)

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