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A Level Biology > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

describe the tracheal system of an insect

A
  1. spiracles = pores on surface that can open / close to allow diffusion
  2. tracheae = large tubes full of air that allow diffusion
  3. tracheoles = smaller branches from tracheae, permeable to allow gas exchange with cells
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1
Q

explain how the body surface of a single-celled organism is adapted for gas
exchange

A

-thin, flat shape and large surface area to volume ratio
-short diffusion distance to all parts of cell → rapid diffusion eg. of O2 / CO2

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2
Q

explain how an insect’s tracheal system is adapted for gas exchange

A

-tracheoles have thin walls
-high numbers of highly branched tracheoles
-tracheae provide tubes full of air
-contraction of abdominal muscles (abdominal
pumping)
-fluid in end of tracheoles drawn into tissues by
osmosis during exercise

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3
Q

explain the impact of tracheoles having thin walls

A

-short diffusion distance to cells

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4
Q

explain the impact of high numbers of highly branched tracheoles

A

-so short diffusion distance to cells
-so large surface area

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5
Q

explain the impact of tracheae providing tubes of air

A

-fast diffusion

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6
Q

explain the impact of abdominal pumping

A

-changes pressure in body
-causing air to move in / out
-maintains concentration gradient for diffusion

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7
Q

explain the impact of fluid in end of tracheoles being drawn into tissues during exercise

A

-lactate produced in anaerobic respiration lowers ψ of cells
-as fluid is removed, air fills tracheoles
-so rate of diffusion to gas exchange surface increases as diffusion is faster through air

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8
Q

explain structural and functional compromises in terrestrial insects that
allow efficient gas exchange while limiting water loss

A

-thick waxy cuticle / exoskeleton → Increases diffusion distance so less water loss (evaporation)
-spiracles can open to allow gas exchange AND close to reduce water loss (evaporation)
-hairs around spiracles → trap moist air, reducing ψ gradient so less water loss (evaporation)

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9
Q

explain how the gills of fish are adapted for gas exchange

A

-gills made of many filaments covered with many lamellae
-thin lamellae wall / epithelium
-lamellae have a large number of capillaries

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10
Q

explain the impact of gills being made of many filaments covered with many lamellae

A

-increases surface area for diffusion

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11
Q

explain the impact of gills having a thin lamellae wall

A

-so short diffusion distance between water / blood

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12
Q

explain the impact of lamellae having a large number of capillaries

A

-remove O2 and bring CO2 quickly so maintains
concentration gradient

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13
Q

describe counter current flow

A
  1. blood and water flow in opposite directions through/over lamellae
  2. so oxygen concentration always higher in water (than blood near)
  3. so maintains a concentration gradient of O2 between water and blood
  4. for diffusion along whole length of lamellae
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14
Q

what would happen if flow was parallel for blood and water

A

-equilibrium would be reached so oxygen wouldn’t diffuse into blood along the whole gill plate

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15
Q

explain how the leaves of dicotyledonous plants are adapted for gas exchange

A

-many stomata (high density) → large surface area for gas exchange (when opened by guard cells)
-spongy mesophyll contains air spaces → large surface area for gases to diffuse through
-thin → short diffusion distance

16
Q

explain structural and functional compromises in xerophytic plants that
allow efficient gas exchange while limiting water loss

A

-thicker waxy cuticle
-sunken stomata in pits / rolled leaves / hairs
-spines / needles

17
Q

what is a xerophyte

A

-plant adapted to live in very dry conditions eg. cacti and marram grass

18
Q

impact of xerophytes having a thicker waxy cuticle

A

-increases diffusion distance so less evaporation

19
Q

impact of xerophytes having sunken stomata in pits

A
  • ‘trap’ water vapour / protect stomata from wind
    -so reduced water potential gradient between leaf / air
    -so less evaporation
20
Q

impact of xerophytes having spines/needles

A

-reduces surface area to volume ratio

21
Q

describe the gross structure of the human gas exchange system

A

-trachea
-bronchi
-bronchioles
-capillary network
-alveoli

22
Q

explain the essential features of the alveolar epithelium that make it
adapted as a surface for gas exchange

A

-flattened cells / 1 cell thick → short diffusion distance
-folded → large surface area
-permeable → allows diffusion of O2 / CO2
-moist → gases can dissolve for diffusion
-good blood supply from large network of capillaries →
maintains concentration gradient

23
Q

describe how gas exchange occurs in the lungs

A

-oxygen diffuses from alveolar air space into blood down its concentration gradient
-across alveolar epithelium then across capillary endothelium

24
Q

explain the importance of ventilation

A

-brings in air containing higher conc. of oxygen & removes air with lower conc. of oxygen
-maintaining concentration gradients

25
Q

explain how humans breathe in (inspiration)

A
  1. diaphragm muscles contract → flattens
  2. external intercostal muscles contract, internal
    intercostal muscles relax (antagonistic) → ribcage pulled up / out
  3. increasing volume and decreasing pressure
    (below atmospheric) in thoracic cavity
  4. air moves into lungs down pressure gradient
26
Q

explain how humans breathe out (expiration)

A
  1. diaphragm relaxes → moves upwards
  2. external intercostal muscles relax, internal
    intercostal muscles may contract → ribcage moves down / in
  3. decreasing volume and increasing pressure
    (above atmospheric) in thoracic cavity
  4. air moves out of lungs down pressure gradient
27
Q

suggest why expiration is normally passive at rest

A

-internal intercostal muscles do not normally need to contract
-expiration aided by elastic recoil in alveoli

28
Q

suggest how different lung diseases reduce the rate of gas exchange

A

-thickened alveolar tissue (eg. fibrosis) → increases diffusion distance
-alveolar wall breakdown → reduces surface area
-reduce lung elasticity → lungs expand / recoil less → reduces concentration gradients of O2 / CO2

29
Q

suggest how different lung diseases affect ventilation

A

-reduce lung elasticity (eg. fibrosis - build-up of scar tissue)
-narrow airways / reduce airflow in & out of lungs (eg. asthma - inflamed bronchi)
-reduced rate of gas exchange

30
Q

how does reduced lung elasticity affect ventilation

A

-lungs expand / recoil less
-reducing volume of air in each breath (tidal volume)
-reducing maximum volume of air breathed out in one breath (forced vital capacity)

31
Q

how does narrow airways affect ventilation

A

-reducing maximum volume of air breathed out in 1 second (forced expiratory volume)

32
Q

how does reduced rate of gas exchange affect ventilation

A

-increased ventilation rate to compensate for reduced oxygen in blood

33
Q

suggest why people with lung disease experience fatigue

A

-cells receive less oxygen → rate of aerobic respiration reduced → less ATP made

34
Q

suggest how you can analyse and interpret data to the effects of pollution,
smoking and other risk factors on the incidence of lung disease

A

-describe overall trend → eg. positive / negative correlation between risk factor and incidence of disease
-manipulate data → eg. calculate percentage change
-interpret standard deviations → overlap suggests differences in means are likely to be due to chance
-use statistical tests → identify whether difference / correlation is significant or due to chance
○correlation coefficient → examining an association between 2 sets of data
○student’s t test → comparing means of 2 sets of data
○ chi-squared test → for categorical data

35
Q

suggest how you can evaluate the way in which experimental data led to
statutory restrictions on the sources of risk factors

A

-analyse and interpret data as above and identify what does/ doesn’t support statement
-evaluate method of collecting data
○ sample size → if large enough to be representative of population
○ participant diversity eg. age, sex, ethnicity and health status → representative of population?
○ control groups → used to enable comparison?
○ control variables eg. health, previous medications → valid?
○ duration of study → long enough to show long-term effects?
-evaluate context → has a broad generalisation been made from a specific set of data?
-other risk factors that could have affected results?

36
Q

explain the difference between correlations and causal relationships

A

-correlation does not mean causation → may be other factors involved

37
Q

what is a correlation

A

-correlation = change in one variable reflected by a change in another - identified on a scatter diagram

38
Q

what is a causation

A

-causation = change in one variable causes a change in another variable

A Level Biology (19 decks)

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