Movement Across Membrane Flashcards
Name the 3 types of movements across menebranes
Diffusion
Osmosis
Active transport
Cell membranes are selctively permeable
What does this mean
. This means that they allow certain
substances to pass through them freely, but they prevent other substances from
passing through.
Substances are allowe to apss through based on there chemical nature and size
What is diffusion
. Diffusion is the movement of molecules from a region of high concentration of molecules to a region of low concentration of molecules until the concentration is the same in both regions
In diffuison
Is there a barrier or energy needed
No there is no barrier and no energy
What is osmosis
Osmosis is the moevment of water from a high water potential to a low
Water potential across a
Selectively permeable membrane until dynamic equilibrium is reached
What is water potential
Water potential is the ability of water, due to its “free” kinetic energy, to move from a region where there is relatively a larger number of water molecules (e.g. pure water), to a region where there is a lower number of water molecules (e.g. a solution).
What reduces the water potential
Solutes reduce the free energy of water molecules, so a solution has a lower potential than pure water.
What is active transport
N.B.: Active transport involves the absorption of substances across a DPM, against
a concentration gradient. Energy is required for active transport to take place.
Explain what happens in active transport
Some organic molecules, such as amino acids and glucose, are too large to pass through the cell membrane
. Proteins in the membrane can actively carry these large molecules through the membrane..
The proteins select which molecules they will carry through the membrane and use energy produced by the mitochondria in the cell to move these molecules through the membrane.
