Topic 1- Diffusion, Osmosis & Active Transport Flashcards
What are the 3 ways substances move in and out of cells?
Diffusion
Osmosis
Active transport
Definition of diffusion
Diffusion is the overall movement of particles from an area of higher concentration to an area of lower concentration.
Where can diffusion occur?
Liquids and gases because the particles are free to move about randomly.
What type of molecules can diffuse?
Only very small ones such as glucose, amino acids, water and oxygen. Big molecules like starch and proteins can’t fit through the membrane.
Definition of Osmosis
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What is a partially permeable membrane?
It is a membrane with very small holes in it so only tiny molecules such as water can pass through but any bigger such as sucrose can’t.
What happens to the water molecules in Osmosis?
They pass through the membrane both ways because the particles move about randomly all the time.
How else could you describe Osmosis?
The net movement of water molecules across a partially permeable membrane from a region of LOWER SOLUTE CONCENTRATION to a region of HIGHER SOLUTE CONCENTRATION. Because a high water concentration means a low solute concentration and a low water Concentration means a high solute concentration.
What is the definition of Active Transport?
Active Transport is the movement of particles across a membrane against a concentration gradient (from an area of lower to an area of higher concentration) using energy transferred during respiration.
How is Active Transport different from Diffusion and Osmosis?
the particles are moved up a concentration gradient rather than down (like Diffusion and Osmosis) and the process requires energy ( unlike Diffusion which is a passive process)
what is a passive process?
A passive process is when it happens by itself and it doesn’t need any extra energy to make it happen.
What experiment do you do to investigate Osmosis?
it involves putting potato cylinders into different concentrations of sucrose solutions to see what effects different water concentrations have on them.
What is the unit for the concentration of the solution?
M. A solution with a concentration of 0.0M is pure water.
What happens at 0.0M?
The cells turn turgid because they are in a dilute solution and so the water penetrates through the membrane.
What happens at 0.25M?
The cells in the solution stay the same because the water can pass through them.
