Diffusion, facilitated diffusion and osmosis Flashcards
What is transported by a diffusion?
Some non-polar molecules can directly pass through the membrane. E.g. O2, CO2,
Factors affecting the rate of diffusion:
- the gradient
- temperature
- the surface area
- the nature of the molecule
Large molecules require…
more energy to get them moving across the membrane.
Non-polar molecules such as…
alcohol and hormones, diffuse much more easily than polar ones. This is because they are soluble in non-polar phospholipid tails.
Large polar molecules such as…
glucose and amino acid cannot diffuse through the phospholipid molecules. They can pass only with a help of transport proteins.
Facilitated diffusion is…
diffusion of substances through transport proteins in the cell surface membrane. Provide hydrophilic areas that allow the molecules or ions to pass through the membrane.
Osmosis is…
a special type of diffusion involving water molecules only
What can be the highest water potential?
0
Water potential is the tendency…
of water to move.
Water potential depends on:
- how much water the solution contains in relation to solutes
- how much pressure is being applied
Water always moves from high water to…
low water potential.
The solute potential decreases with…
higher concentration of solutes.
A decrease in solute potential causes…
a decrease in water potential.
Pressure potential is the contribution…
of pressure to water potential and solute potential.
Increasing pressure potential…
increases the water potential.
Osmosis in animal cells:
- cells do not contain cell wall
- if the water potential is not equal to the water potential in the cell, the cell would either shrink or burst
Plant cells are surrounded by…
cell wall, which is strong and rigid.
The cell wall pushes against expanding…
protoplast, so the pressure builds up.
Expanding protoplast increases…
the water potential until the water potential is equal in and outside of the cell. (Fully rigid)
Plasmolysis is the process…
of shrinking protoplast when plant cells become plasmolysed.
Incipient plasmolysis is the point…
at which pressure potential just reached 0 and plasmolysis is about to occur.
