B3.1 Gas Exchange Flashcards
how does gas exchange occur
through diffusion
gas exchange
exchange of respiratory gases between/organisms and the environment
challanges of gas exchange
- surface area to volume ratio decreases with size increase
- surface area is large in relation to amount of cytoplasm
- most cells are too far from surface to recieve enough oxygen by diffusion
- increased metabolic rate and demand for oxygen is high
properties of gas exchange surfaces
permeability
thin tissue layer
moisture
large surface area
permeability
to allow gases across
thin tissue layer
to make shortest distance for diffusion as possible
moisture
gases dissolve in moisture, helping them to pass across gas - exchange surface
large surface area
for large quantities of gas
concentration gradient
the different in concentration of a substance between one area and another
steeper the gradient
faster the diffusion
why does gradient need to be maintained
allows O2 to diffuse into the body and Co2 to go out
How are the gradients maintained
dense network of blood vessels which provide large surface area
continuous blood flow carrying away O2 and CO2 to surface
Ventilation
Lungs
organ where gas exchange occurs
thin, large, moist surface area
are in a protected position in thorax so air has to be brought to surface
thorax
upper part of body separated from the abdomen
ventilation system
moves air into and out of lungs efficiently and maintains concentration gradients
blood circulation system
moves O2 to cells as soon as it crosses surface
respiratory pigment
increases O2 carrying ability of blood
haemoglobin in RBC
Intercoastal muscles
between ribs involved in ventilation
diaphragm
sheet of tissues largely muscle, separating thorax from abdomen in mammals
pleural membrane
lines lungs and thorax cavity
secretes pleural fluid
Trachea
windpipe
bronchus
tube connecting trachea with lungs
bronchiole
small terminal branch of a bronchus
alveolus
air sac in lung
walls supported by rings of cartilage preventing collapse due to change in pressure
pleural fluid
lubricating liquid protecting lungs from friction
alveoli adaptation
elastic connective tissue as apart of their walls
small size and large number
large surface are for gas exchange
capillary system in alveoli
wraps around alveoli and provides a large surface area for diffusion of O2 and CO2
connected to pulmonary vein and artery supplied with blood
surfactant role
lines inner surface of alveoli
secreted by cells and reduces surface tension allowing alveoli to flex easily
where does gas exchange occur
alveoli
how does gas exchange occur in alveoli
goes into RBC and combines with haemoglobin to form oxyhaemoglobin
on inspiration action alveoli
volume of thorax increases
walls of alveolus and terminal bronchiole are stretched in
air is drawn in
on expiration action alveoli
volume of thorax decreases
alveolus and terminal bronchiole revert to resting size, due to recoil of elastic fibres
air is expelled out
how effective are mammalian lungs
air flow is tidal - enters and leaves by the same route
residual volume that cant be expelled
incoming air mixes with and dilutes the air
Ventilation of lungs
air drawn into alveoli when air pressure in the lungs is lower than atmospheric pressure
air forced out when pressure is higher in lungs than atmospheric pressure
inspiration steps
- external intercoastal muscles contract
- internal relax
- diaphragm contracts and moves down
- ribs move upwards and downward
expiration steps
- external intercoastal muscles relax
- internal contract
- diaphragm relax and moves up
- ribs move downward and inward
measurement of lung volume
spirometer
plastic lid over a tank that rises and falls while breathing
tidal volume
typically 400-500 cm3
volume of air normally exchanged in breathing
have potential for an extra large intake and an extra large expiration of air
inspiratory reserve
different between the max inspiratory level and tidal volume
expiratory reserve
different between the maximum expiratory level and tidal volume
vital capacity
total amount of air exhaled after maximal inhilation
VC
TC+IRV+ERV
Ventilation rate
number of inhalations or exhalations per minute
epidermis
outer layer
mesophyll tissue
parenchyma cells containing chloroplasts
vascular tissue
xylem and phloem of plants
vascular bundle
strands of xylem and phloem separated by cambium
the site of water and food movements up and down the stem
palisade mesophyll
cells containing many chloroplasts found beneath the upper epidermis in leaves
spongy mesophyll
rounded cells in the leaves that are loosely packed, creating air spaces where air circulates, providing a large surface area for gas exchange
stomata
pore in epidermis of a leaf, surrounded by 2 guard cells
turgid
where vacuoles of a plant cell is full of water, pushing the cell membrane against the cell wall
flaccid
plant cell that has become soft and less rigid than normal because the cytoplasm with cells has shrunk and contracted away from cell walls through water loss
adaptations of leaf for gas exchange
waxy cuticle
epidermis
air spaces
spongy mesophyll
stomatal guard cells
veins
waxy cuticle adaptation
impermiable barrier so gases and water vapour go through stomata
water loss reduced
epidermis adaptation
contain stomata for gas exchange - reduce water loss
air spaces adaptation
allow gases to circulate - maintains concentration gradients
spongy mesophyll adaptation
large surface area for gas exchange
stomatal guard cells adaptation
open and close to control gas exchange and water loss
veins adaptations
carry water to leaves which is then lost through stomata
required for photosynthesis
Transpiration
evaporation of water from the spongy mesophyll tissue and subsequent diffusion through stomata
factors affecting rate of transpiration
temperature
humidity
wind
light intensity
temperature affecting rate of transpiration
increase in kinetic energy and faster diffusion
increased temp = increased transpiration
humidity affecting rate of transpiration
high humidity slows transpiration
wind affecting rate of transpiration
sweeps away water vapour on stomata increasing concentration of water
light intensity affecting rate of transpiration
stomata tend to open in light and cause loss of water vapour
stomatal density
leaf cast to determine
