gas exchange Flashcards
what is an exchange surface
where molecules leave and enter the cell
which cells can exchange materials with the environment
unicellular
which cells can not exchange materials with the environment
multicellular - as cells are often to far away from the surface, so takes to long for the molecules to diffuse
what is the relationship bwt SA and vol
-amount of material an organism needs to exchange with its environment is PROPORTIONAL to its volume
-amount it can exchange is PROPORTIONAL to SA
what is the equation for diffusion in terms of SA:V
SA x difference in conc./ length of diffusion path or thickness of exchange surface
what is the relationship bwt SA and V
as volume increases SA:V decreases
what features do good exchange surfaces have
-a large SA- makes SA:V so molecules can cross the surface per unit time
-a thin surface- shorter diffusion pathway - so more molecules per unit time across surface
-a steep diffusion gradient- greater conc gradient increases rate of diffusion so more molecules across surface per unit time
how is a diffusion gradient maintained
movement of an a environmental medium (air/water) and the movement of the internal medium (blood)
how can certain environmental effects exchange surfaces
water and air have different properties due to heat transfer
- air - molecules apart - so air is a poor conductor
- water - molecules close- more heat conducted- loss heat more easily- so need adaptions to survive
what must larger organisms have to increase SA
-a specialised organ
-circulatory system with oxygen-carrying pigment eg Hb
how to fund volume
length x height x width
how to find surface area
length x height x 6
how to find SA:V
divide SA by V
what type of skeleton does an insect have
an exoskeleton made of chitin
how is the exoskeleton adapted to prevent water loss
waxy cuticle - prevents dehydration and allows insect to live on land
how is the insect tracheal system structured
spiracles are located in the thorax and abdomen
spiracles branch into tracheoles
tracheoles surrounded by rings of chitin
how do the spiracles prevent water loss
they can open and close - short periods of gas exchange
what other feature of the insect prevents water loss
-hairs on entrance to spricale - trap layer of thin air and reduce conc gradient
how does the insect system allow for sufficient gas exchange
extensive branching system - large SA for gas exchange to occur over
maintenance of diffusion gradient - using a ventilation mechanism which increases the conc gradient- O2 used in tissues for respiration so conc is lower in the cells- higher conc of CO2 in the cells
thin membrane - shorter diffusion pathway - tracheole walls very thin and narrow which makes them permeable due to the lack of chitin
- also a withdrawal of fluid in exercise - so air reaches more cells on the exchange surface
what is the effect of exercise on fluid in the tracheoles
-at rest
tracheoles contain watery fluid
reduces SA over which diffusion can occur
this is not a problem when at rest as respiration rate is lower
-during strenuous activity
muscles respire anaerobically - produce lactate
lactate lowers water potential in the muscles
water moves from tracheole into muscle
gas diffuses faster through air than water
greater SA exposed to air
so more gas exchange occurs