B2 - Diffusion, Osmosis and Active Transport Flashcards
How do substances move in and out of cells?
By diffusion, osmosis and active transport.
What is diffusion?
The net overall movement of particles from an area of higher concentration to an area of lower concentration.
(The gradual movement of particles from a place where there are lots to a place where there are fewer.
If something moves from an high concentration to a area of lower concentration, what is it said to have done?
Moved down a concentration gradient .
What state of matter does diffusion happen in?
Gas and liquid
Why does diffusion happen in both liquids and gases?
The particles can move freely
Diffusion continues till what?
Diffusion continues till the concentration of the diffusing particle is even in both areas
Give an example of diffusion.
The smell of perfume diffuses through a room
What does ‘partially permeable membrane’ mean?
Only Small molecules can pass through the membrane.
Give an example of a partially permeable membrane on a cell.
Cell membrane
Give an example of small molecules that can pass through a cell membrane. (4)
Glucose
Amino acid
Water
Oxygen
Name three big molecule that can’t fit through cell membranes.
Starch
Sucrose
Protein
What is osmosis?
Then net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
How do the water molecules pass through the membrane during osmosis?
They move both ways because water molecules move randomly.
If there is sucrose solution on one side of the membrane and water on the other then what movement can you expect?
There is a steady flow of water into the region with fewer water molecules (into a stronger sugar solution)
What is active transport?
The movement of particles across a membrane against a concentration gradient using energy transferred during respiration (e.g. from an area of lower concentration to an area of higher concentration)
