gas exchange Flashcards
what is fick’s law?
surface area x difference in conc / diffusion distance
name three features of an efficient gas exchange system
● large surface area
● short diffusion distance
● steep conc gradient (maintained by blood supply or ventilation)
what is ventilation?
breathing
what is the trachea?
wind pipe
what is the thoracic cavity?
space where the lungs are
describe the pathway taken by air in the human gas exchange system (4)
● trachea - bronchi - bronchioles - alveoli
● happens down a pressure gradient
● alveoli - diffuse across alveolar epithelium and capillary endothelium - capillary - haemoglobin in blood
● happens down a diffusion gradient
describe the human gas exchange system (5)
● as you breathe in, air enters trachea
● trachea splits into 2 bronchi
● each bronchus branches off into smaller tubes called bronchioles
● bronchioles end in small air sacs called alveoli
● ribcage, intercostal muscles and diaphragm work together to move air in and out
explain inspiration (6)
● external intercostal muscles contract
● ribcage - moves upwards and outwards
● diaphragm contracts to flatten
● increasing volume of thoracic cavity
● as volume increases, lung pressure decreases (to below atmospheric pressure)
● air flows down the trachea and into lungs down pressure gradient
what does inspiration require?
energy (active)
explain expiration (5)
● external intercostal and diaphragm muscles relax
● ribcage moves downward and inwards
● diaphragm becomes curved
● volume of thoracic cavity decreases, causing pressure to increase (to above atmospheric pressure)
● air forced down pressure gradient and out of lungs
what does expiration not require?
energy (passive)
explain forced expiration (4)
● external intercostal muscles relax
● internal intercostal muscles contract
● pulling ribcage further down and in
● movement of 2 sets of intercostal muscles are antagonising
what are alveoli made from?
alveolar epithelium
what is the alveolar epithelium made of?
a single layer of thin, flat squamous cells
what is the capillary endothelium?
type of epithelium that forms the capillary wall
outline how human gas exchange happens in the alveoli (4)
● oxygen diffuses out alveoli, across the alveolar epithelium and capillary endothelium
● into haemoglobin in red blood cells
● carbon dioxide diffuses from blood across capillary endothelium and alveolar epithelium and into alveoli and is breathed out
● movement happens down a diffusion gradient
how are alveoli adapted for gas exchange? (4)
● short diffusion distance - alveolar epithelium is made of squamous cells (thin exchange surface)
● large surface area - large number of alveoli means there’s a large surface for gas exchange and folds in alveolar epithelium
● steep concentration gradient of O2 and CO2 between alveoli and capillaries
● capillaries provide good blood supply
what is the composition of gases inhaled? (3)
● higher conc of O2
● N2 stays the same
● lower conc of CO2
what is the composition of gases exhaled? (3)
● lower conc of O2
● N2 stays the same
● higher conc of CO2
what is forced expiratory volume (FEV1)?
maximum volume of air that can be breathed out in 1 second
what is forced vital capacity (FVC)?
maximum volume of air that can be breathed forcefully out after a deep breath
what is tidal volume? (2)
● tidal volume is the volume of air in each breath
● average 0.4 - 0.5dm^3
what is ventilation rate? (2)
● number of breaths per minute
● average 15
what is pulmonary ventilation? (2)
● volume of air ventilated by the lungs in 1 minute
● PV (dm^3) = tidal volume x ventilation rate
how does pulmonary fibrosis slow gas exchange? (3)
● scar tissue makes alveoli thicker
● reduces elasticity of alveoli
● increases diffusion distance
how does TB slow gas exchange? (3)
● scar tissue makes alveoli thicker
● reduces elasticity of alveoli
● increases diffusion distance
how does asthma slow gas exchange? (2)
● tidal volume reduced
● decreases conc gradient
how does lung cancer slow gas exchange? (2)
● tidal volume reduced
● decreases conc gradient
how does emphysema slow gas exchange? (3)
● reduced elasticity
● prevents exhalation
● decreases conc gradient
correlation doesn’t equal
causation
why can’t insects use their bodies as an exchange surface? (2)
● waterproof, chitin exoskeleton that is impermeable to gases
● and a small SA:V (in order to conserve water)
describe an insects exoskeleton (3)
● made of chitin
● impermeable to gases
● waterproof
what is a spiracle? (2)
● opening in the exoskeleton of insects body
● most of the time closed to avoid water loss
describe the pathway taken by air in the insect gas exchange system (4)
● spiracle
● tracheal tubes
● tracheoles
● respiring cells
explain the process of gas exchange in insects (2)
● gases move in and out of the tracheal tubes and tracheoles through the spiracles
● conc gradient allows oxygen to diffuse into respiring cells while waste CO2 diffuses out
how are insects adapted for gas exchange? (3)
● highly branched tracheoles - increases surface area
● tracheoles have thin walls - short diffusion distance
● cells constantly respiring & abdominal pumping (a form of ventilation) - maintains conc gradient
describe abdominal pumping (3)
● linked to carbon dioxide release
● raises pressure in body
● CO2 is pushed out of body / moves down pressure gradient into atmosphere
why can’t fish use their bodies as an exchange surface?
● waterproof, impermeable outer membrane
● small SA:V ratio
outline how insects control water loss? (2)
● closes spiracles
● waterproof waxy cuticle and tiny hairs around spiracles - reduce evaporation
describe the pathway taken by water in a fish (3)
● mouth
● over lamellae (oxygen diffuses into blood stream)
● out of gills
describe the structure of a fish’s gills (4)
● gill arch
● gill filaments attached to gill arch
● gill lamellae on the surface of each gill filament
● gill lamellae contain capillaries
explain the process of gas exchange in fish
● fish opens mouth to enable water to flow in
● water passes over the lamellae, oxygen diffuses into blood stream
● waste CO2 diffuses back into water and flows back out of gills
how are fish adapted for gas exchange? (3)
● many gill filaments that are highly branched with lamellae - increases surface area
● ventilation + blood flow + counter current flow - maintains concentration gradient
● lamellae have thin walls(epithelium) - decreases diffusion distance
what is counter-current flow? (3)
● blood and water flow in opposite directions - through and over the lamellae
● there is a conc gradient maintained along entire lamellae
● O2 conc between water and blood does not reach equilibrium
describe the structure of a dicotyledonous plant (7)
● waxy cuticle
● upper epidermis - layer of tightly packed cells
● palisade mesophyll layer - layer of elongated cells containing chloroplasts
● spongy mesophyll layer - layer of cells that contains network of air spaces
● stomata - pores (usually) on underside of the leaf which allows air to enter
● guard cells - pairs of cells that control the opening and closing of stomata
● lower epidermis - layer of tightly packed cells
describe how dicotyledonous plants are adapted to gas exchange (5)
● large surface area - main gas exchange surface are mesophyll cells inside leaf
● when guard cells are turgid (full of water), stoma open allowing air to enter leaf
(opposite of turgid is flaccid)
● air spaces within spongy mesophyll layer allows CO2 to rapidly diffuse into cells
● conc gradient maintained - CO2 is quickly used up in photosynthesis by cells containing chloroplasts
● short diffusion distance - thinness of plant tissues and stomata so no active ventilation is required
how do dicotyledonous plants control / limit water loss? (3)
● stomata regulated by guard cells
● close to stop water loss by transpiration
● most stay closed to prevent water loss while some open to let oxygen in
what is the singular for stomata?
stoma
how are xerophytic plants adapted to reduce transpiration? (4)
● waxy cuticle - increases diffusion distance
● spines of cactus - decreases surface area
● rolled leaf - decreases surface area and conc gradient
● stomata sunken In pits - decreases conc gradient
how do you draw scientific drawings? (10)
● no shading
● label lines need to be parallel
● label lines need to be on one side
● no hanging lines
● no sketched lines
● draw with sharp pencil
● labels with ruler and with pen
● use key for magnification
● add title
● no arrow heads
what is the formula for aerobic respiration?
C6H12O6 + 6O2 —> 6CO2 + 6H2O
what is the formula for photosynthesis?
6CO2 + 6H2O –(light)–> C6H12O6 + 6O2
