Studied by 4 people
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration.
What is osmosis?
diffusion of water from a high water concentration to a low concentration across a selectively permeable membrane
What is active transport?
substances moving from an area of low concentration to an area of high concentration (against the concentration gradient)
examples of diffusion
Perfume odour filling a room
sugar dissolving evenly in water
during photosynthesis when CO2 diffuses into the leaves
dipping teabags in hot water
dust and smoke particles diffusing into the air causing pollution
examples of osmosis
swelling of raisins and other seeds when put in water
movement of salt water in the animal cell across our cell membrane
gargling salt water when you have a cold
the uptake of water into a plant
examples of active transport
uptake of glucose by epithelial cells
the transport of amino acids across the intestinal lining in the gut
secretion of proteins (eg. enzymes)
active process
the cell provides energy (ATP) to power the transport process
passive process
substances cross the membrane without any energy input from the cell
turgid
swollen with water, hard, plant cells ONLY
what can speed up the process of diffusion?
higher concentration gradient, temperature, mitochondria, size of particles, thickness and surface area of membrane
what do cells need to take in for respiration?
glucose and oxygen
what do cells need to get rid of?
waste products and chemicals needed elsewhere
respiration equation
C6H12O6 + 6O2 --→ 6CO2 + 6H20 + Energy
concentration
The spread of something over a given area.
concentration gradient
difference in the concentration of a substance from one location to another
examples of waste products in cells
urea
what dissolved substances move in and out of the cell membrane?
waste products, oxygen, carbon dioxide, glucose
how have cells adapted to have a higher surface area for diffusion to occur?
villi- sticking out "tentacles" to intake nutrients in small intestines
root hair cell- "tail" jutting out from main body, helps intake water and nutrients from the soil in the roots
partially permeable membrane
a membrane that allows only certain substances to pass through
dilute solution
a solution that contains a small amount of solute
concentrated solution
a solution containing a large amount of solute
why can't membranes let all particles in
some particles are too big
solvent
water
solute
A substance that is dissolved in a solution.
hypertonic
less solute inside the cell, more on outside
hypotonic
more solute inside the cell, less outside
isotonic
when the concentration inside and outside the cell are the same
what occurs when a cell is hypertonic
the water moves out of the cell to try and equalise the outer solution
what occurs when a cell is hypotonic
water moves in to try and equalise the inner solution.
what occurs when a cell is isotonic
nothing
how does the size of a hypertonic cell change
as water moves out, it undergoes plasmolysis and shrivels
how does the size of a hypotonic cell change
as water moves in, it grows bigger and may pop if too big (known as cytolysis). Plant cells don't go undergo cytolysis but become turgid
how does the size of a isotonic cell change
it doesn't change
why can't a plant cell undergo cytolysis
it has a cell wall meaning it can't pop, so they become turgid, meaning they have too much water
cytolysis
The rupturing of a cell due to excess internal pressure (due to water)
plasmolysis
This happens when a cell shrinks inside its cell wall while the cell wall remains intact.
crenated
Shrinkage of cells giving crinkled appearance
potato osmosis experiment independent variable
concentration of solution
potato osmosis experiment dependent variable
percentage change of the mass of the potato
potato osmosis experiment control variable
the surface area of the potato pieces, temperature of the room, temperature of the solution, the amount of time in the solution, the amount of solution in each test tube
what is the expected trend in the data for the potato osmosis experiment
the cells were hypotonic but becomes hypertonic, so the potato began with a percentage increase in mass but when the cells became hypotonic, there was a percentage decrease in mass
whats the formula for the potato osmosis percentage change in mass?
difference in mass/starting mass x 100
in the potato osmosis experiment why is the potato dried before weighing
so the water/starch don't add to the start/end mass
flaccid
limp, not firm; lacking vigor or effectiveness (hypertonic)
amoeba
large surface area compared to its volume, can rely on simple diffusion, osmosis ad active transport to exchange materials with the outside world
how does a higher concentration gradient speed up diffusion?
particles on a concentration gradient want it to be equal on both sides so the biggest the difference the quicker they want to rectify this
how does a higher temperature speed up diffusion?
more kinetic energy to move and mix more quickly
how does a larger surface area speed up diffusion?
more area to intake/remove particles
common features of an exchange surface
large surface area
thin membrane
in animals, efficient blood supply, capillaries to take away +bring diffused substances
in animals, being ventilated
how are gills adapted for exchanging materials
large surface area
large surface area of blood capillaries
short distance required
outer layer of the gill filaments and the capillary walls are just 1 cell thick
Note 
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