Transport in Cells Flashcards
what is diffusion?
The random movement of particles from an area of high concentration to an area of low concentration (down a concentration gradient) until there is no net movement and equilibrium is reached.
what state can diffusion occur in?
- solid
- gas
what is a concentration gradient?
difference in concentration
the bigger the concentration gradient…
the faster the rate of diffusion
why does temperature affect diffusion?
- higher temp
- particles carry more energy and move around faster
- faster rate of diffusion
how does surface area affect diffusion?
- larger surface area of membrane
- more contact
- more particles can pass through
- faster rate of diffusion
how does diffusion distance affect diffusion?
- shorter diffusion distance
- particles can go through more quickly
- faster rate of diffusion
list 4 factors which affect diffusion
- concentration gradient
- temp
- surface area
- diffusion distance
small organisms have a higher SA:V ratio than larger organisms
- diffusion can happen through a large area of small organism
- makes diffusion useful for transporting molecules
large multicellular organisms have a small SA:V ratio
- need transport system with specialised surface to exchange molecules
- cells are too far from the environment
-
how are alveoli adapted to transfer gases in the lungs?
large surface area
if an animal has a large SA:V ratio…
it can lose heat quickly
what type of molecules can diffuse through a cell membrane?
- small molecules e.g oxygen, glucose, amino acids and water
- big molecules can’t fit through membrane e.g proteins and starch
what does concentration mean?
mass of a solute per unit volume
does diffusion require energy?
- no
- particles still move randomly
- but concentration of different areas stay the same
explain why we dissolve cocoa powder into warm milk instead of cold
- higher temp provides particles more energy
- diffusion will be quicker
what is osmosis?
the movement of water particles from a region of high water concentration to a region of low water concentration across a partially permeable membrane
how is diffusion and osmosis different?
diffusion: gases and solids
osmosis: water particles
what is partially permeable membrane?
one with very small holes in it
what state can osmosis occur in?
water
what type of molecules is allowed in osmosis?
- tiny molecules e.g water
- bigger molecules can’t e.g sucrose
describe how the water would move in this scenario
1) right-hand side more dilute, higher concentration of water
2) allows water to go through semi-permeable membrane into the left-hand side, lower concentration of water
3) after an hour: fresh water level drops, brine water level rises
what specialised plant cell uses osmosis to absorb water?
root hair cell
water doesn’t diffuse…
it moves by osmosis
in an osmosis experiment, give an example of the independant variable
concentration of sugar solution
in an osmosis experiment, give an example of the dependant variable
change in the mass of the object being used
what is an isotonic solution in regard to a cell?
same water concentration inside and outside the cell
what is a hypotonic solutionin regard to cell?
- outside is more diluted than inside
- water will go into the cell (osmosis)
what is a hypertonic solution in regard to a cell?
- inside the cell is more diluted than outside
- water will move into the more concentrated (osmosis)
normal blood glucose concentration is 8 grams per litre. suggest the possible glucose solutions that are isotonic, hypotonic and hypertonic
isonotic: 8
hypotonic: any number below 8
hypertonic: any number above 8
what is active transport?
movement of particles from an area of low concentration to an area of high concentration across a cell membrane
give examples of active transport in humans and plants
- mineral absorption in plants: necessary for healthy growth
- sugar absorption in human gut: needed for cell respiration
does active transport require energy?
- yes
- required to absorb subtances against a concentration gradient
- cells need lost of mitochondria to release energy
- proteins from cell membrane
how do root hair cells take in minerals using active transport?
allows plant to absorb mineral ions from a dilute solution against a concentration gradient
what is passive transport?
- diffusion
- osmosis
why do root hair cells have lots of mitochondria?
- need lots of energy
- for active transport of minerals
explain the transport of glucose into the blood in the small intestine
- higher concentration of glucose will diffuse naturally into the blood
- level of concentration even out in the blood and gut
- active transport occurs to gain more glucose into bloodstream
- then transfered to cells, used for respiration
how do humans exchange substances such as urea?
- urea diffuses from cells into the blood plasma
- for removal from the body by the kidneys
what is the job of the lungs?
- transfer oxygen to blood
- remove waste CO2 from it
- lungs contain alveoli where gas exchange takes place
how are alveoli adapted to have max diffusion of oxygen and CO2?
- large surface area
- moist lining for dissolving gases
- very thin walls
- extensive blood supply
how does villi provide a big surface area?
- inside of small intestine covered in villi
- increases SA so digested food is absorbed more quickly into blood
- has single layer of surface cells
- extensive blood supply to assist quick absorption
how does stomata help to diffuse CO2 into air spaces of leaf and then into the cell?
- underneath of leaf (exchange surface) covered in stomata which CO2 diffuses in through
- oxygen and water vapour diffuses out through stomata
- guard cells close stomata cells if plant is losing water faster than it is being replaced by the roots
how does the shape of leaf make diffusion more effective?
- thin
- increases area of exchange surface
how does the walls of the cells in a leaf make diffusion more effective?
- air spaces inside leaf increases area of exchange surface
- more chance for CO2 to enter cells
