Transport across membranes Flashcards
what are the 3 mechanisms for transport?
- active transport
- facilitated diffusion
- osmosis
what does the term passive mean ?
doesn’t require energy
what energy does active transport require?
energy in the from of ATP
Give the definition of diffusion
Movement of substance from a region of their higher concentration to a region of their lower concentration
what is a concentration gradient ?
the difference in concentration of two areas
what is the difference in two concentration areas called?
concentration gradient
what is dynamic equilibrium?
When substances are evenly spread although still moving
what factors is the rate of diffusion affected by?
- surface are
- thickness of surface
- concentration gradient
- size
- temperature
- water solubility
How does the surface area affect diffusion ?
the grater the surface area the faster the rate of diffusion
How does the concentration gradient affect diffusion ?
the steeper the gradient the faster the rate of diffusion
How does the thickness of the exchange surface affect diffusion ?
the thinner the surface the faster the diffusion
smaller diffusion pathway
How does the temperature affect diffusion ?
the higher the temperature the faster the rate of diffusion as molecules have ore energy
How does the water solubility affect diffusion ?
non-polar molecules diffuse faster than polar ones
show fixks law
rate of surface area x difference in concentration
diffusion=———————————————————-
thickness of exchange surface
how can you increase the diffusion rate?
- maximise surface area
- maximise concentration difference
- minimise thickness of exchange surface
what is osmosis?
A type of diffusion for water molecules
what is the water potential of a solution?
the tendency for water to move from one place to another
give the units of water potential
kPa
give the definition of osmosis
the movement of water across a partially permeable membrane down a water potential gradient
what is a hypertonic solution?
concentrated solution or low water potential
what is a hypotonic solution?
dilute solution or high water potential
what is simple diffusion ?
diffusion directly across the phospholipid bilayer
what is facilitated diffusion?
the transport needed for a specific molecule
what do channel proteins do ?
allow charged substances to diffuse
