Transport across membranes Flashcards
Define diffusion.
Diffusion is the passive net movement of particles from a high concentration to a low concentration.
What is a passive process?
A passive process is one where no energy is needed for it to happen.
What are the factors that affect the rate of diffusion?
The concentration gradient- particles diffuse faster when there is a high concentration gradient(large difference in concentration).
Thickness of the exchange surface- the thinner the surface, the faster the particles travel
Size of molecules- small molecules move faster than large molecules and therefore diffuse faster.
At higher temperatures, particle have more kinetic energy so diffuse faster
The larger the surface area of the plasma membrane, the faster the rate of diffusion
Define osmosis.
Osmosis is when water molecules diffuse through a partially permeable membrane from an area of higher water potential to an area of lower water potential.
What are isotonic solutions?
This is when two solutions have the same water potential.
There’s no net movement of water molecules because there’s no difference in water potential between the cell and the surrounding solution.
What are hypotonic solutions?
This is when a solution has a high water potential compared to the inside of the cell.
What would happen to an animal cell in a hypotonic solution?
An animal cell in a hypotonic solution will swell and eventually burst due to the water diffusing into the cell via osmosis. (Lysis)
What would happen to a plant cell in a hypotonic solution?
If a plant cell was placed into a hypotonic solution, the vacuole will swell and the contents of the vacuole and cytoplasm will push against the cell wall. This causes the cell to become turgid (swollen) but the cell won’t burst because the inelastic cell wall is able to withstand the increase in pressure.
What are hypertonic solutions?
These are solutions with a lower water potential than the cell.
What would happen if an animal cell was placed into a hypertonic solution?
The animal cell would shrink. (Crenation)
What would happen if a plant cell was placed into a hypertonic solution?
The plant cell would become flaccid (limp). The cytoplasm and plasma membrane will eventually pull away from the cell wall. This is called plasmolysis.
What is water potential ?
The tendency of a solution to lose water.
How is water potential decreased?
From the addition of a solute
What is facilitated diffusion?
The diffusion of particles through carrier and channel proteins in the plasma membrane.
Define active transport
Active transport uses energy to move molecules and ions across the plasma membrane against the concentration gradient
