1.15 to 1.17 cell transport (diffusion, osmosis and active transport) Flashcards
What is simple diffusion?
The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient
What molecules enter and leave cells via simple diffusion through the cell membrane?
Small molecules e.g. oxygen, water, glucose, amino acids
What factors affect the rate of diffusion? (3)
● Temperature
● Concentration gradient
● Surface area of cell membrane
Define osmosis
The net movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane
What is active transport?
The movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy
How is a percentage change in mass calculated?
% change = ((final mass - initial mass0 / initial mass) x 100
which type of molecule is too large to diffuse through a cell membrane? (1)
glucose, proteins are too large to diffuse through a cell membrane
in which of these scenarios is osmosis occurring?
A: water is moving from the mouth down into the stomach
B: sugar is being taken up into the blood from the gut
C: a plant is absorbing water from the soil
D: oxygen is entering the blood from the lungs (1)
C (osmosis involves the movement of WATER molecules across a partially permeable membrane)
Dilute solution?
A solution that contains a relatively small amount of dissolved solute
Concentrated solution?
A solution that contains a relatively large amount of dissolved solute
Solute?
A dissolved substance in a solution such as glucose or salt
Partially permeable membrane?
A membrane which allows some substances through but not others
Turgidity?
When a plant cell is swollen due to the movement of water into the cell
Flaccid?
When water moves out of the plant cell causing the cell to change shape and the vacuole to shrink
Plasmolysis?
When water has completely moved out of plant tissue by osmosis and the vacuoles are empty
Molarity?
The amount of substance in a certain volume of solution
Cork borer?
A device used to make plant tissue cylinders of the same diameter
Mass?
The measure of the amount of matter in an object measured in grams or kilograms
Top pan balance?
A set of scientific measuring scales with an exposed pan
Surface moisture?
The moisture covering the surface of the plant tissue that must be removed to ensure valid results
Distilled water?
Water that has been evaporated and condensed and contains no dissolved solutes
The concentration of solution….
The independent variable or factor that is changed in this experiment to investigate the effect of osmosis in plant tissue
The mass or length of plant tissue….
The dependent variable or factor that is measured in this experiment to investigate the effect of osmosis in plant tissue (investigation of osmosis in potatoes)
Temperature, time, plant tissue diameter, volume of solution …..
The variables that are controlled to ensure the experiment is a fair test
Expected results
Plant material such as potato chips kept in dilute solutions will increase in mass or length, plant material kept in concentrated solutions will decrease in mass or length
Passive process
Substances undergoing diffusion cross the membrane without any energy input from the cell
Concentration gradient
The difference in concentration of a substance
Factors affecting diffusion
Concentration gradient, temperature and surface area
temperature in diffusion
Particles move more and diffuse quicker in warmer environments
Surface area to volume ratio?
The amount of surface area in relation to how large something is
Large surface area to volume ratio in diffusion
Leads to faster diffusion rates, as there is more room for particles to diffuse through a membrane
Active process
A process that requires energy, such as active transport
