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OCR A-Level Biology > Chap 7 - Exchange Surfaces & Breathing > Flashcards

Chap 7 - Exchange Surfaces & Breathing Flashcards

1
Q

Describe how diffusion distance, SA, volume, SA:V ratio vary with increasing organism size.

A
  • diffusion distance between cells where oxygen is needed and the supply of oxygen increases
  • surface area increases
  • volume increases at a faster rate than surface area so the SA:V ratio will decrease
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2
Q

State the formulae for the circumference and area of a circle.

A
  • area of a circle: r2π
  • circumference of a circle: 2rπ
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3
Q

Describe how the level of activity of an organism is related to demand for oxygen and glucose.

A
  • high levels of metabolic activity means more energy will be required by the organism
  • this energy is released through respiration which requires glucose and oxygen so the demand will be higher
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4
Q

Explain how volume is related to demand

A
  • as volume of organisms increases they get larger and are made up of more cells
  • these cells will require glucose and oxygen supply in order to carry out respiration in order to carry out vital bioprocesses hence why demand and volume are related
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5
Q

Explain how surface area is related to demand

A
  • some organisms are able to use their surface as their supply of oxygen so for a greater surface area more oxygen can be supplied (if volume kept constant)
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6
Q

Explain why supply meeting demand requires adaptations as organisms increase in size.

A
  • they are made up of more cells that all require constant and large supply of O and removal of CO2
  • their metabolic rate is usually higher meaning more respiration needs to occur
  • diffusion distances will increase - not possible to supply cells deeper inside the organism through just the surface
  • smaller SA:V ratio - slow diffusion and gases cant be exchanged fast enough or in large amounts
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7
Q

Explain how surface area to volume ratio affects the need for a specialised exchange system.

A
  • as organisms get larger, SA:V gets smaller and distances substances need to travel from outside to reach cells in center of body get longer
  • this makes it harder and ultimately impossible to absorb enough oxygen through the available surface area to meet the demands of the body
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8
Q

State 4 features of efficient exchange surfaces.

A
  • increased surface area
  • thin layers
  • good blood supply
  • ventilation to maintain diffusion gradient
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9
Q

Explain how increased surface area increases efficiency of exchange surfaces. + example

A
  • provides area needed for exchange and overcomes the low SA:V ratio of larger organisms, increasing diffusion rate
  • example: villi in small intestine
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10
Q

Explain how thin layers increase efficiency of exchange surfaces. + example

A
  • distances that substances need to diffuse are short, increasing the rate of diffusion - more efficient
  • example: alveoli in lungs
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11
Q

Explain how a good blood supply increases efficiency of exchange surfaces. + example

A
  • steeper concentration gradient means faster diffusion
  • means that substances are constantly delivered to and removed from exchange surfaces
  • this maintains steep conc gradient
  • example: gills
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12
Q

Explain how ventilation increases efficiency of exchange surfaces. + example

A
  • for gases ventilation system helps maintain conc gradient, making it more efficient
  • example: gills
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13
Q

Describe the structure of the nasal cavity & explain how its structure makes it adapted for its function

A
  • main function: allow air to enter lungs at a similar temp and humidity to the air there & prevent dust particles/pathogens from entering
  • large SA + good blood supply - warms air to body temp to maintain
  • hairy lining - secretes mucus to trap dust and bacteria protecting lung tissue
  • moist surfaces increase humidity of incoming air reducing evaporation from exchange surfaces
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14
Q

Describe the structure of the trachea & explain how its structure makes it adapted for its function

A
  • main function: airway carrying clean warm moist air from nose into chest
  • wide tube supported by flexible cartilage - stop collapsing
  • incomplete cartilage rings - food can move easily down oesophagus behind the trachea
  • lined with ciliated epithelium with goblet cells - secrete mucus to trap dust and pathogens which is moved away by cilia to be swallowed and digested
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15
Q

Describe the structure of the bronchi & explain how its structure makes it adapted for its function

A
  • trachea divides to form left and right bronchi that lead to left and right lungs
  • similar structure to trachea but smaller & have complete cartilage rings
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16
Q

Describe the structure of bronchioles & explain how its structure makes it adapted for its function

A
  • bronchi divide to form small bronchioles
  • no cartilage rings
  • smooth muscle - when contracts, they constrict and when it relaxes they dilate, changing amount of air reaching the lungs
  • thin flattened epithelium lining - some gas exhange possible
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17
Q

Describe the structure of bronchioles & explain how its structure makes it adapted for its function

A
  • bronchi divide to form small bronchioles
  • no cartilage rings
  • smooth muscle - when contracts, they constrict and when it relaxes they dilate, changing amount of air reaching the lungs
  • thin flattened epithelium lining - some gas exhange possible
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18
Q

Describe the structure of alveoli & explain how its structure makes it adapted for its function

A
  • tiny air sacs - main gas exchange surface of body
  • consist of flattened epithelial cells, collagen and elastic fibres (elastin)
  • elastic fibres - allow alveoli to stretch when air is drawn in, when they return to their resting size they help squeeze air out - elastic recoil of lungs
  • large SA - high rate of diffusion
  • thin layers - 1 epithelial cell thick
  • good blood supply - surrounded by a lot of capillaries - constant flow of blood = maintained steep conc gradient
  • good ventilation - breathing moves air in/out maintaining steep gradient for both diffusions
  • lung surfactant - thin solution layer the inner surface is covered with that makes it possible for alveoli to remain inflated
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19
Q

Explain how ciliated epithelial cells and goblet cells of trachea and bronchi work together to protect the lungs.

A
  • goblet cells secrete mucus on the lining of trachea/bronchi to trap dust/microorganisms
  • cilia beat and move mucus along with everything trapped in it away from lungs
  • most goes into throat to be swallowed and digested
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20
Q

Describe the importance of elastic fibres in the function of alveoli.

A

allow alveoli to stretch with inhale, return to resting size with exhale - elastic recoil of lungs

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21
Q

Describe the importance of lung surfactant in the function of alveoli.

A

thin solution layer the inner surface is covered - makes it possible for alveoli to remain inflated at the end of exhalation

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22
Q

Explain how mammalian gas exchange system is adapted to be an efficient exchange surface.

A
  • large surface area of alveoli
  • constant ventilation of the lungs
  • short diffusion distances in the alveoli
  • good blood supply through the network of capillaries
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23
Q

Define breathing

A

the process of taking air into and expelling it from the lungs

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24
Q

Define ventilation

A

movement of air in and out of the lungs as a result of pressure changes in the thorax brought about by breathing movements.

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25
Q

Define gas exchange

A

the transfer of oxygen from inhaled air into the blood and the transfer of carbon dioxide from the blood into the exhaled air.

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26
Q

Define inspiration

A

the act of drawing air into the lungs

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27
Q

Define expiration

A

the act of expelling air from the lungs

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28
Q

Define active process

A

process that requires ATP

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29
Q

Define passive process

A

process that does not require ATP

30
Q

Describe the process of inspiration linking the action of muscles to the movement of strucrtures, change in pressure within the lungs and direction of airflow.

A
  • diaphragm contracts - flattens and lowers
  • external intercostal muscles contract, moving ribs upwards and outwards
  • volume of thorax increases so pressure in thorax is reduced
  • lower pressure in thorax than atmospheric pressure - air drawn thru nasal passages, trachea, bronchi and bronchioles into the lungs until equalibrium
31
Q

Describe the process of normal expiration linking the action of muscles to the movement of strucrtures, change in pressure within the lungs and direction of airflow.

A
  • diaphragm relaxes and domes upwards
  • external intercostal muscles relax, ribs move down and inwards
  • alveolar elastic fibres recoil to normal length
  • volume of thorax decreases so pressure in thorax increased
  • higher pressure in thorax than atmospheric pressure - air moves thru bronchioles, bronchi, trachea, nasal passages out of the lungs until equilibrium
32
Q

Describe how the process of forced expiration is different from normal expiration and suggest when it might be used.

A
  • internal intercostal muscles contract, pulling ribs down hard and fast
  • abdominal muscles contract forcing diaphragm up to increase pressure in lungs rapidly
  • neither type of muscle is used in normal expiration
  • no muscles contract during normal expiration - a passive process
  • forced expiration is an active process
33
Q

State 3 pieces of equipment used to measure functioning of the lungs. Outline how each works.

A
  • peak flow meter - measures how fast air comes out of lungs when exhaling forcefully and inhaling fully
  • vitalograph - patient exhales forcefully as quickly as possible thru mouthpiece and instrument produces graph of amount of air they breathe out and how quickly breathed out
  • spirometer - breathe in/out of trapped volume of air this moves the float/lid, changing the volume as it goes up/down
34
Q

Explain why a spirometer cannot measure absolute lung volume.

A

there is no way of knowing the volume of air remaining in the lungs after a maximal expiration.

35
Q

Define tidal volume

A

volume of air entering/leaving hte lungs in a normal breath

36
Q

Define inspiratory reserve volume

A

max additional volume of air that can be inhaled after a normal inhalation

37
Q

Define expiratory reserve volume

A

additional volume of air that can be exhaled after a normal exhalation

38
Q

Define residual volume

A

volume of air that is left in your lungs when you have exhaled as hard as possible

39
Q

Define vital capacity

A

maximum volume of air that can be forcefully exhaled after a maximal inhalation

40
Q

Define total lung capacity

A

sum of vital capacity and residual volume

41
Q

Define breathing rate

A

number of breaths per minute

42
Q

Define ventilation rate

A

total volume of air inhaled in 1 minute

43
Q

Explain how to calculate breathing rate from spirometer trace.

A
  • divide number of breaths by time taken for them to happen in s-1,
  • multiply that by 60 to get min-1
44
Q

Explain how to calculate tidal volume from spirometer trace.

A
  • count squares for TV for certain number of breaths
  • take average of that
45
Q

Write equation linking ventilation rate with breathing rate and tidal volume.

A

ventilation rate = tidal volume x breathing rate (per min)

46
Q

Describe how a spirometer trace would differ during exercise as compared to the trace before exercise started.

A
  • tidal volume increases
  • breathing rate increases
  • downward trend increases bc greater rate of O2 use
47
Q

Describe how tidal volume and breathing rate link to oxygen uptake and explain the importance of the change in tidal volume and breathing rate during exercise.

A
  • greater tidal volume - more air moves into lungs - more oxygen uptake
  • greater breathing rate - ventilation increases therefore oxygen uptake also increases
  • important to meet demands of tissues when exercising bc they will produce more CO2 and demand more O2
48
Q

Define exoskeleton

A
  • external skeleton of some organisms (eg insects)
  • made of chitin in insects, impermeable to water
49
Q

Define spiracle

A

small openings along the side of insects where air enters and leaves the body

50
Q

Define trachea

A
  • largest tubes of insect respiratory system that lead away from spiracles
  • kept open by spirals of chitin
  • have waxy cuticle - impermeable to gases
51
Q

Define tracheoles

A
  • narrow tubes formed from branching of tracheae
  • single elongated cells with no chitin lining/cuticule, permeable to gases
52
Q

Define tracheal fluid

A
  • fluid lining found towards the end of tracheoles
  • oxygen dissolves in it
  • slows down gas diffusion
53
Q

Outline the structure of the insect gas exchange system and describe the way oxygen reaches the body cells.

A
  • oxygen enters through spriacles, into tracheae which branch into narrow tracheoles, moves by simple diffusion at rest
  • tracheae - waxy cuticle & rings of chitin make them impermeable
  • tracheoles - 1 each is 1 greatly elongated cell with no chitin lining - freely permeable to gases
  • oxygen dissolves in moist walls of tracheoles(tracheal fluid), diffusing across the single cell into tissue cells, CO2 in opposite direction
54
Q

Explain why insects tend to keep spiracles closed when oxygen demands are low.

A

when air enters and leaves the system, water is also lost - prevents water loss

55
Q

Describe the adaptations of the insect gas exchange system that make it an efficient exchange surface.

A
  • spiracles for air to diffuse in, can be opened and closed to minimise water loss when oxygen demand low
  • high surface area for gas exchange due to branching of tracheae
  • tracheoles - single cells - short diffusion distance
  • during exercise, muscle movements ventilate tracheae and maintain concentration gradient
  • during exercise, lactic acid draws out more tracheal fluid which increases surface area for oxygen absorption
56
Q

Describe how activity changes the volume of tracheal fluid in tracheoles and explain the value of this occurring.

A
  • lactic acid from anaerobic respiration builds up in the tissues
  • this draws fluid out, exposing greater surface area for more oxygen uptake into body cells
  • important bc exercise means oxygen demand increases
57
Q

Describe two adaptations that insects with very high energy demands have to increase efficiency of their gas exchange system.

A
  • mechanical ventilation of tracheal system
  • air pumped into system by muscular pumping movements of thorax and or abdomen
  • movements change volume of body - changes pressure in tubes, causing air in/out
  • collapsible enlarged trachea or air sacs
  • act as reservoirs, inflated/deflated by ventilating movements of thorax and abdomen
58
Q

Describe the advantages of, and challenges faced by, gas exchange systems operating in water rather than air.

A
  • advantage - no need to minimise water loss
  • challenges - water is a lot denser & more viscous, has lower oxygen content
59
Q

Define operculum

A

bony flap covering gills of bony fish

60
Q

Define buccal cavity

A

space before the gills (mouth cavity)

61
Q

Define operculum valve

A

valve attached to operculum that allows water in/out of opercular cavity

62
Q

Define gill arch

A
  • bony support for gills
  • each gill made of 4
  • lined with hundreds of thin, flat gill filaments
63
Q

Define gill filament

A
  • thin plates attached to gill arch that have folds called lamellae
  • give gills high surface area
64
Q

Define gill lamellae

A
  • folds on gill filaments that contain a network of capillaries
  • site of gas exchange
65
Q

Describe the mechanism of inspiration in bony fish.

A
  • mouth opened
  • operculum closed
  • buccal cavity floor lowers
  • buccal cavity expands
  • water rushes into mouth
66
Q

Describe the mechanism of expiration in bony fish.

A
  • mouth closed
  • operculum open
  • buccal cavity floor raises
  • buccal cavity shrinks
  • water rushes out of mouth
67
Q

Describe adaptations that make bony fish gas exchange system an efficient exchange surface.

A
  • gill filaments & lamellae allow for very high surface area for diffusion
  • rich blood supply to lamellae maintain steep conc gradient
  • thin layers - short diffusion distances
  • tips of adjacent gill filaments overlap - resistance to flow of water increased and water movement decreased - more time to perform gas exchange
  • countercurrent exchange system - water & blood move in opposite directions to maintain steep conc gradient to extract as much oxygen as possible
68
Q

Define countercurrent exchange system

A

system for exchanging materials or heat when the two different components flow in opposite directions past each other

69
Q

Define parallel exchange system

A

system for exchanging materials or heat when the two different components flow in the same direction, parallel to each other

70
Q

Describe how a much higher oxygen saturation of the blood can be achieved by a countercurrent exchange system as compared to a parallel exchange system

A
  • concentration gradient between water and blood maintained all along
  • oxygen continues to diffuse down gradient - much higher level of oxygen saturation of blood is achieved
  • in parallel, diffusion takes place until oxygen and water conc are in equilibrium, no further net movement of oxygen into blood occurs

OCR A-Level Biology (16 decks)

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