Gas Exchange Flashcards
gas exchange
oxygen is taken in and used for aerobic respiratio
oxygen is terminal electron acceptor in etc
carbon dioxide is excreted - has low pH which can change pH of blood, causing enzymes to denature
active cells respire more so demand more o2- contracting muscle cells + cells that synthesise lots of complex molecules
Efficient gas exchange
highly folded/branched surface to increase surface area
very thin surfaces creating a short diffusion path
a transport system (large blood supply) to maintain steep conc gradient
semi permeable surface to allow selected materials across
Lungs
trachea- kept open by rings of cartilage, lined with ciliated epithelium, have mucus secreting goblet cells
bronchi- have mucus and ciliated epithelium to trap microbes and dirt- cilia sweeps it away
bronchioles- walls are made of muscle which constrict and control flow of air
alveoli- air sacs at the end of bronchioles, made up of single layer epithelium, elastic fibres allowing them to stretch and recoil
Mechanics of breathing
air moves down a pressure gradient
inspiration- external intercostals contract, diaphragm contracts, rib cage moves up and out, thoracic cavity vol. increases so pressure decreases and air moves in
expiration- internal intercostals contract, diaphragm relaxes, rib cage moves down, thoracic cavity vol. decreases, pressure increases so air moves out
Spirometer
tidal volume- volume of air breathed in and out at rest
vital capacity- max vol. of air that can be breathed in or out
residual vol. - vol of air remaining in lungs after forcible expiration
pulmonary ventilation- volume of air respired in one minute (tidal volume x bpm)
Single celled organisms
gas exchange surface is cell surface membrane
o2 diffuses into cell through the semi permeable membrane and co2 diffuses out
short diffusion path
large surface area: volume ratio
conc gradient- o2 higher outside than in
co2 lower outside than in
Adaptations- single celled
as organisms increase in size they must be able to get enough o2 and food to all their systems + remove waste products
their volumes get larger so they evolve to have-
elongated and flattened shape to increase SA:V
specialised exchange systems
Insects
developed an exoskeleton made of chitin (impermeable)
-can conserve water and support its body outside of
water
tracheal system- openings called spiracles to access o2
connect to tracheae (air filled tubes) which divide into highly branches tracheoles
every cell is only a short distance from a tracheole
anaerobic exercise produces lactate which lowers wp so water moves from high wp in tracheoles to low wp in muscle cells, decreases volume in tracheoles so pressure is lower than in atmosphere which draws air in from atmosphere
Efficient gas exhange- insects
tracheoles have thin walls- short diffusion path
tracheoles are highly branched- short diffusion path and large SA for gas exchange
tracheae fill with air for steep conc gradient
can pump abdomens when active by contracting muscles to help move air deeper into tracheoles
when muscles relax the air pressure is lower in the tracheal system so air moves in from outside
-more air enters muscles from tracheoeles, quicker which maintains conc gradient with atmoshphere
Fish
gill filaments and lamellae increase SA of gills which increases rate of gas exchange
gill filaments have lamellae on them which increase SA
need specialised system or diffusion would be too slow to provide o2 for aerobic resp
operculum- opening on side of body
water flow over gills is maintained by opening of mouth, operculum shuts, floor of mouth is lowered, water enters due to decreased pressure (inc. volume), operculum opens, mouth closes, increased pressure (dec. volume) pushes water over gills
Efficient gas exchange- fish
water flows in opposite direction to blood- countercurrent flow ensures diffusion gradient is maintained across whole lamellae so more o2 is absorbed and can be used for respiration
lamellae are folded increasing SA
thin epithelium for short diffusion path
steep conc gradient maintained as circulation replaces blood saturated with o2
Plants
o2 from ps can be used in resp
co2 from resp can be used in ps
spongy mesophyll cells are the gas exchange surface
leaves are thin and have many stomata so no cell is far from the external air so the diffusion pathway is short.
spongy mesophyll has lots of air spaces so they provide a large surface area for rapid diffusion since they are not tightly packed
mitochondria and chloroplasts use up co2 and o2 quickly
co2 is used quickly by photosynthesising cells which maintains conc gradient
Limiting water loss
evaporation from leaves- transpiration
stomata close to prevent water loss
thick inner wall of guard cells = stomata open
thick waxy cuticle- increases diffusion pathway length so slower diffusion, impermeable to water
hairy leaves- traps moist air so wp gradient is reduced so less water is lost by evaporation
leaves are rolled which protects lower epidermis trapped air has high wp so there is no wp gradient- no water loss
sunken stomata- traps moist air next to stomata which reduces wp gradient
human lungs adapted
lots of alveoli have folded walls to increase SA
thin alveoli epithelium and thin capillary endothelium provide short diffusion pathway
large capillary network in lungs maintains steep conc gradient
ventilation and circulation maintains steep conc gradient
insects limit water loss
exoskeleton is waterproof due to lipid layer
small sa:v where water can evaporate from
spiracles where gas enters and water leaves are very small and can open and close to reduce water loss
