Movement of Substances : Transport Processes Flashcards
what is diffusion?
- the random movement of particles from an area of high concentration to an area of lower concentration
why do all particles move randomly?
- all particles move randomly and in different directions all the time due to their kinetic energy
what does diffusion describe?
- the overall direction and speed of the movement
what is it called when over time, all of the particles will be equally distributed?
equilibrium
does equilibrium mean that the particles stop moving?
no!
describe the speeds and rates for diffusion and osmosis.
- diffusion and osmosis can happen at different speeds or rates
what are the four main factors which affect the rate of diffusion?
- temperature
- concentration gradient
- distance
- surface area : volume
how can temperature affect the rate of diffusion?
- at higher temperatures, molecules have more kinetic energy and so move faster
- therefore diffusion occurs faster
how does concentration gradient affect the rate of diffusion?
- if there is a very large difference in concentration between two areas, molecules will diffuse from the higher to the lower concentration quickly
- if the concentration gradient (difference) is small, diffusion will happen more slowly
how does distance affect the rate of diffusion?
- diffusion takes longer if the molecules have to travel further, molecules don’t travel in a straight line which slows the process
- therefore cells are small as smaller volume reduces distance
how does surface area: volume affect the rate of diffusion?
- a larger SA speeds up the rate of diffusion as there are more opportunities for the molecules to move, which is why surfaces such as alveoli in lungs are so large
- SA:V is more significant, as the two oppose each other: an efficient exchange surface has a surface area which is very large compared to the distance the molecules must travel
- SA:V is increased when structures are small
what do cells rely on for their function?
- diffusion
what is osmosis?
- a special type of diffusion
- it is only ever used to describe the movement of water molecules across a membrane
what is the definition of osmosis?
- osmosis is the net diffusion of free water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane
draw a diagram to represent and describe free water molecules.
one note page
draw a diagram to represent and describe partially permeable molecules.
one note page
what is water potential?
- a measure of the concentration of free water molecules in a solution
- pure water has a water potential of 0
- as a solute is added, water potential falls as there will be a lower concentration of free water molecules
- concentrated solutions have a very low water potential.
what are constantly moving in and out of cells?
- free water molecules
how do animal and plant cells react to being placed in different concentrations and why?
- they react differently
- this is because plant cells are placed in different solutions
what is an isotonic solution?
- when the solution outside the cell has the same water potential as inside the cell - no net movement
what is a hypotonic solution?
- when the solution outside the cell has a higher water potential then inside the cell - net movement of free water molecules into the cell
what is a hypertonic solution?
- when the solution outside the cell has a lower water potential then inside the cell- net movement of free water molecules out of the cell
draw a diagram to describe as to how an animal vs a plant cell would react in a hypotonic solution.
one note page
draw a diagram to describe as to how an animal vs a plant cell would react in an isotonic solution.
one note page