Exchanging substances Flashcards
why does gas exchange happen in the lungs?
in order to transfer oxygen to the blood and remove waste carbon dioxide from it, the lungs contain alveoli where gas exchange takes place
what are alveoli?
millions of little air sacs in the lungs
how are the alveoli specialised to maximise diffusion of oxygen and carbon dioxide?(4)
*they have an enormous surface area (around 75^2 in humans)
*they have a moist lining for dissolving gasses
*they have very thin walls
*they have a good blood supplyto help maintin a concentration gradient
what are villi?
millions of tiny little projections in the small intestine
why is the small intestine covered in villi?
to increase the surface area in a big way to that digested food is absorbed much more quickly into the blood
what are the features of villi (2)
*a single lauer of surface cells
*a very good blood supply to assist quick absorption
how are the structure of leaves adapted to let gases diffuse in and out?
•the underneath of a leaf is an exchange surface, covered in little holes called stomata which carbon dioxide diffuses in through and oxygen and water vapour. diffuse out of
•the flattened shape of the leaf increases the area the leaf’s underneath exchange surface to increase effectiveness
•the walls of water cells inside the leaf are an exchange surface also and the air spaces inside the leaf increase the area of this surface so there is more of a chance for carbon dioxide to get into cells
how does water vapour escape from a leaf?
•it evaporates from the cells inside the leav
•it escapes by diffusion as there is a lot of it inside and less of it in the air outisde
what are gills?
the gas exchange surface in a fish
how are the gills adapted for effective gas exchange of oxygen into the blood and carbon dioxide out of the blood(4)?
*each gill has lots of gill filaments which give big surface area for gas exchange
*gill filaments are covered in lamellae which also increase surface area
*lamellae have lots of blood capillaries to speed up diffusion
*they have a thin surface layer of cells to minimise the distance gases have to diffuse
how does oxygen diffuse from the water into the blood of a fish?
•water (containing oxygen) enters the fish through the mouth and passes out through the gills
•blood flows through the lamellae in one direction and water flows over in the opposite direction to maintain a larger concentration gradient between the water and the blood
•the concentration of oxygen in the water is always higher than that in the blood so as much oxygen of as possible diffuses from the water into the blood
