gas exchange

features of specialised gas exchange surfaces

• large sa

• very thin surfaces

• permeable

• good blood supply

• good supply of external medium (animal specific)

• conc. gradient for diffusing gases (animal specific)

• have layer of moist

gas exchange in insects

• have spiracles instead of lungs — small openings that insects are covered in

• open into tracheae which divide into tracheoles which perfuse muscle fibres, delivering oxygen/ removing carbon dioxide

• gases passively diffuse through tracheae + tracheoles — sufficiently fast to meet tissue requirements

• spiracles close to prevent water loss + lower demand of gas exchange

• spiracles open when there's high carbon dioxide levels and low oxygen levels

• end of tracheoles can fill with water, limiting diffusion rate

• anaerobic respiration occurs in muscles = lactic acid

• draws water out from tracheoles to muscles so diffusion rate increased

mechanical assistance

• helps insects with high metabolic rates gain more oxygen when passive system isn’t providing enough

• insects contract thorax as it moves

• creates pressure diff. down which air draws into tracheoles

collapsible tracheae + air sacs

• helps insects with high metabolic rates gain more oxygen when passive system isn’t providing enough

• some tracheae able to collapse + attached to air sacs

• creates reservoir of trapped, oxygenated air for future use

gills adaption

• high sa

• rich + continuous blood flow

• water moving through gills continually

gas exchange

exchange of gases at cells + tissues through diffusion; occurs at alveoli + respiring tissues

respiration

release of atp from organic compounds; occurs in cells

ventilation

movement of air in + out of lungs, facilitating gas exchange; breathing

adaption of lungs

• alveoli = high surface area + secrete surfactant which prevents alveoli walls from adhering to each other + provides moist surface for gas exchange

• alveoli surrounded by capillary bed

  • maintains high concentration gradient for oxygen + carbon dioxide between blood + alveoli

ventilation - inspiration

• diaphragm contracts + moves down

• external intercostal muscles contract, internal relax

• ribcage up + out

• vol. of thorax increases, lung pressure decreases

• air passively moves from high pressure surrounding air to low pressure lungs

what do plants lower metabolism compared to mammals mean for them?

simpler gas exchange system

what happens to the stomata in high light intensity?

it closes

where and how does gas exchange occur in plants?

• via diffusion directly in + out tissues of plant

• e.g. roots from soil

• e.g. above ground through leaves (stomata + gas exchange surfaces within leaf) + lenticels

what gases enter and exit the leaf when light intensity increases? why?

• carbon dioxide in

• oxygen out

• photosynthesis taking place

lenticels

• loosely packed cells in stem/bark that allow diffusion between cells

• allows diffusion between atmosphere + internal tissues of stem

• bark relatively impermeable — gases can’t pass directly through

• lenticels in stem/bark of woody plants to allow this to happen

where does the oxygen for respiration in leaves come from? where does it go through?

comes from soil through permeable cell wall + membranes in root tissues

what happens when the soil’s oxygen is limited? what’s an example of something that could cause this?

• resp. + subsequent growth = limited

  • e.g. waterlogged

guard cells change in _____

turgor pressure

when a guard cell is turgid the stomata…

opens

when a guard cell is flaccid the stomata…

closes