Diffusion, Osmosis And Active Transport Flashcards
Define diffusion
The net movement of molecules or ions from a region where they are highly concentrated to one where their concentration is lower
What 3 factors affect diffusion
Concentration gradient
Area over which the diffusion takes place
Thickness of exchange surfaces
How does the concentration gradient affect the rate of diffusion
The greater the difference in concentration of molecules/ions on either side of the exchange surface, the faster the rate of diffusion
How does the type of area that diffusion takes place in affect the rate of diffusion
The larger the area of the exchange surface, the faster the rate of diffusion
How does the thickness of the exchange surface affect the rate of diffusion
The thinner the surface, the faster the rate of diffusion
How does the type of molecule affect diffusion
The size and nature of the diffusing molecule affects diffusion
Are smaller molecules or larger molecules faster
Smaller
Are water soluble molecules or lipid soluble molecules faster
Lipid soluble
Are polar molecules or non polar molecules faster
Non polar
What can’t ions do
Pass through/diffuse across a membrane
What does facilitated diffusion require
A protein molecule
Where does protein molecules for facilitated diffusion come from
The cell membrane
What are the 2 types of protein molecule
Channel protein or carrier protein
What are channels? What does this allow?
Channels are hydrophilic
They allow water soluble ions and molecules (eg glucose) to pass through
What is movement in facilitated diffusion? What does that mean
Passive
This means it doesn’t use energy
How selective is facilitated diffusion
Very
It only allows 1 kind of molecule to go through which has to be complementary to the protein
When does net movement occur in facilitated diffusion
When there is a difference in concentration
What is osmosis
The passage of water from a region of high water potential to a region of low water potential across a partially permeable membrane
What is the unit for water potential
Psi ψ
What is the water potential of pure water
Zero
What does adding a solute to pure water do?
Lowers its water potential making it more negative
The more solute added the more negative the pH
What can you do to make water potential more negative
Add a solute
What are the types of solutions in osmosis
Hypotonic
Isotonic
Hypertonic
What is a hypotonic solution
Where the solution outside of the cell has a higher solute concentration than the inside of the cell
The water potential is higher outside the cell
Where does the water move to when a cell is placed in a hypotonic solution
It moves into the cell by osmosis
Where does the water move to when a cell is placed in an isotonic solution
There is no net movement because the concentration is the same in and out of the cell
Where does the water move to when a cell is placed in a hypertonic solution
The water moves out of the cell by osmosis
What is an isotonic solution
The concentration of solutes is the same in and out of the cell
The water potential is equal in the solution and the cell
What is a hypertonic solution
Where the solution inside of the cell has a higher solute concentration than outside the cell
There is a lower water potential outside of the cell
What is active transport
Movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using energy and carrier molecules
What is the process of active transport
1 - the molecule binds to receptors on carrier proteins
2 - the hydrolysis of ATP (ATP splitting in to ADP and Pi) releases energy
3 - the carrier protein changes shape due to the energy
4 - the molecule is released on to the other side of the membrane
Which of the movements of molecules are passive
Diffusion, facilitated diffusion, osmosis
Which of the movements of molecules are active
Active transport
Which of the movements of molecules have a high to low concentration gradient
Diffusion, facilitated diffusion and osmosis
Which of the movements of molecules have a low to high concentration gradient
Active transport
Which of the movements of molecules have carrier proteins
Facilitated diffusion, active transport
Which of the movements of molecules do not have carrier proteins
Diffusion and osmosis
Give an example of a molecule that is transported by diffusion
Oxygen
Carbon dioxide
Give an example of a molecule that is transported by osmosis
Water
Give an example of a molecule that is transported by facilitated diffusion
Ions
Give an example of a molecule that is transported by active transport
Glucose ions
