transport in cells Flashcards
what is diffusion?
gradual movement/ spreading out of particles from areas of high concentration to areas of low concentration
how do substances move in/out of cells? (process)
- diffuse through cell membranes
- net movement from area of low concentration to high concentration
what substances are diffused in/out of cells?
- oxygen and carbon dioxide through gas exchange
- urea from cells to blood plasma for excretion in kidney
what factor affect rate of diffusion? (4)
- temp (hotter = faster)
- surface area (larger = faster)
- size of particle (smaller= faster)
- concentration gradient (higher = faster)
how are single-celled organisms adapted to increase rate of diffusion?
large surface area : volume ratio
what are features of exchange surfaces that increase diffusion? (4)
- large surface area/ surface area:vol ratio
- well - ventilated
- good blood supply
- walls are one cell thick/ very thin
why does having walls that are one cell thick/ very thin increase the rate of diffusion?
shorter diffusion path so faster rate of diffusion
why does having a good blood supply/ being well ventilated increase the rate of diffusion?
mantains a steep concentration gradient which leads to a faster rate of diffusion
why does having a large surface area increase rate of diffusion?
more space for diffusion to take place so faster rate of diffusion
what is osmosis?
movement of water molecules across a partially permeable membranne from an area of low concentration to an area of high concentration
in what type of solution will a cell become flacid and why?
**hypertonic **- more concentrated solution than in the cell so water moves OUT of cell
in what type of solution will a cell become turgid and why?
hypotonic - less concentrated solution than in call so water moves INTO cell
why can animal cells burst when they are turgid but plant cells cannot?
- too full of water so pop eg red blood cells
- plant cells cannot pop because of strong cellulose cell wall
how are lungs adapted for exchanging materials (gas exchange)?
maximise diffuision of O2 and CO2 through having:
- very large surface area (~75m^2 for humans) due to alveoli
- very thin wallls ( one cell thick)
- good blood supply
what is active transport?
- moving of substances across cell mebranes against the concentration gradient (from a lower to higher concentration)
- requires energy from respiration
how are root hair cells adapted for active transport?
- large surface area to increase rate of active transport
- lots of mitochondria to respire and provide energy for active transport
describe an experiment to investigate the effect of a range of concentrations of salt solutions on the mass of plant tissues - method (5)
- cut a potatoe into ‘chips’ of the same size, measured using a ruler. weigh to find mass and record in a table
- pour same volume of sugar solutions of increasing concentration into 3 beakers
- place one chip in each beaker for a set amount of time eg 5 minutes.
- after the set amount of time, take each chip out of the solution and dry evenly with a paper towel
- reweigh the chips and calculate the % mass change
how is the small intestine adapted for exchanging materials through diffusion?
suface covered in villi which are covered in micro villi
- increases surface area
- thin walls
- very good blood supply
in what type of solution will a cell stay normal and why?
isotonic - equilliberum so same concentration of water in cell as in the solution
describe an experiment to investigate the effect of a range of concentrations of sugar solutions on the mass of plant tissues - variables
IV - concentration of sugar solution
DV - mass change of chip
CV - size of chip, time chip left in solution for, if the chips are towel dried before weighing the second time, type of potatoe, temp, volume of each solution
what are passive process vs active processes of exchanging matterials?
passive (don’t require energy)
- diffusion
- osmosis
active (require energy)
- active transport
describe a use of active transport in animals
used in digestive system where there is a lower concentration of nutrients in the gut than the higher concentration of nutrients in the blood, but nutrients still need to be moved into the blood
describe a use of active transport in plants
higher concentration of mineral ions and nutrients in root cell than in the soil but minerals and nutriets still need to move into the root cell
how does an increase in temp lead to a higher rate of diffusion?
particles have more energy so move faster across the cell membrane so faster rate of diffusion
what is a partially permeable membrane?
a membrane that allows some some small molecules to pass through eg water but not larger molecules eg sucrose
