P1 - 2d movement of substances in and out of cells Flashcards
what is diffusion?
it is the movement of particles from a region where their concentration is higher to a region where their concentration is lower.
why is the diffusion of gases and solutes important?
all living things use diffusion, substances move in and out of cells by diffusion
- respiration and gas exchange in plants
- obtains many of their requirements
- rid of waste products
how do substances move into and out of cells?
they move through the membrane, it is permeable to many substances
where does the energy for diffusion come from?
energy for diffusion comes from kinetic energy (from the random movement of molecules and ions)
what is a concentration gradient?
a model showing a high place of concentration and a low place (it gets lower as the concentration decreases)
how does surface area influence diffusion?
the greater the surface area to volume ratio the shorter time is will take to diffuse
how does temperature influence diffusion?
diffusion in hot water occurs more rapidly than in cold water.
how does concentration gradient influence diffusion?
the higher the concentration gradient the quicker the diffusion
how does distance influence diffusion?
the rate of diffusion does change so its quicker for diffusion to happen in a shorter distance
what is osmosis?
net movement of water molecules from a region of higher water potential to a region of lower potential, through a partially permeable membrane
what is water potential?
- how freely the water molecules can move
the concentration of water or H2O molecules in a solution
what happens if a plant can’t get enough water to the vacuole?
it becomes less rigid and the plant wilts
- cell wall doesn’t allow for the plant cell to break
how do you investigate the effect of osmosis?
- peel potatoes
- cut cylinders using a cork borer
- trim so same length
- measure the mass of cylinders
- place each cylinder into a separate test tube, add 10cm^3 of 0.5 molar sugar solution
- 0.25 molar sugar solution to the second
- and distilled water to the third
- leave overnight
- take out and dry
- measure mass
- calculate % change
change in value / original value x 100
in the practical, why did the mass of the potato in test tube 2 not change?
because there were equal amounts of water in the potato and in the sugar solution no osmosis occurred
when do the potatoes gain mass?
when put in water
when do potatoes lose mass?
when put into a concentrated solution (of sugar)
turgid plant cell
when it gains lots of water
flaccid plant cell
when it loses water
what is plasmolysis?
its when the plant loses so much water that the cytoplasm and vacuole pull away from the cell wall
how does water enter root hair cells?
osmosis
what is active transport?
it moves substances from a more dilute concentration to a more concentrated solution (against the concentration gradient)
where does active transport get its energy?
from respiration
how do protein molecules move particles across a membrane in active transport?
transport proteins can bind to specific molecules and transport them into the cell
(they can change their shape to make it happen)
- this process also uses energy supplied by respiration
describe the practical to test the factors that influence diffusion
- investigate temp by beetroot
1. cut two equally sized beetroot pieces using cork borer
2. rinse beetroot
3. put water into two test tubes
4. keep one at room temp and put another in a water bath set to temp investigating
5. leave test tubes for a few mins
6. add beet pieces, then after ten mins observe colour in both test tubes
what is osmoregulation?
the homeostatic control of water potential across membranes within the body
how is the human body adapted to maintain optimum osmotic balance?
sweating
increasing and decreasing urine concentration
