Topic 3A- exchange and transport systems Flashcards
the bigger the organism the…
smaller the SA:V ratio
volume of a sphere
4/3XpiXr*3
how do substances get in and out of a single-cell
diffusion, over the small distance of a cell surface memebrane
meaning it is quick
reletivley large surface area compared to volume
how do multicellular organisms move substances
specialised exchange organs
e.g. lungs
what is mass transport
efficient systems to carry substaces to and fromtheir individual
in mammals, this is usually refered to the circulatory system
2 points- distance and surface area
why can multi-cellular organisms not use diffusion alone
1-cells deep within the body means that there is a big distance between them and the the outside environment
2-large animals have a low SA:V ratio, difficult for enough substances to be exhanged that will meet the large volume of a relitivley small surface area
mass transport in plants
transportation of water and solutes in the xylem and phloem
how does body size influence heat exchange
having a large volume means there is a big distance for the heat to travel
small organisms need a higher metabolic rate to generate enough heat
how does body shape influence heat exchange
a smaller surface area means less heat loss
foxes
adaptations for heat loss:
arctic fox-small ears and round fave reduce surface area
african fox- large ears and pointed nose maximising surface area
ficks law
what features increase the rate of diffusion
large surface area, short diffusion pathway and concerntration gradient
why is water needed in plants
- solvent-allow gases to dissolve
- hydrolysis reactions
- photosynthesis
- make the cell turgid(rigid)
pores on the epidermis layer of a plant
stomata
what controls the opening and closing of stomata
guard cells
why is the mesophyll layer surrounded by water
so the co2 can dissolve
why is the mesophyll layer known as ‘spongy’
space within it so co2 can diffuse much quicker to the cells
what does a vacuole do
pushes to organelle’s to the side meaning the chloroplasts are compacted to the side
meaning more of chance for light to it them for photosynthesis
where does photosynthesis take place
chloroplasts
why are plant cells in a pallisade shape
so they can all fit together, resulting in light being more likely to hit a chloroplast
opposite
equation for photosynthesis and respiration
carbon dioxide +water <> oxygen +glucose
why do stomata close at night
to keep moisture in, photosynthesis isnt happening due to no sunlight
what are the pores on insects called
spiricles
what are the advantages of insects having an exoskeloton
protection and prevnts water loss
what is an insects exoskeleton made from
chitin (B glucose) and a nitrogenous group
do insects have a large or small SA:V ratio
small
so cant rely on diffusion alone