Guided notes -- The Cell Membrane and
PASSIVE Cell Transport
 Cell membrane- separates the components of a cell from its ___________________
(what surrounds the cell) and ______________ the passage of materials into and out
of a cell.
 Composed of a _____________________ (75-95%), and ______________ (5-25%).
 Membrane proteins are used for; _________________, ______________,
_____________, ______________, ___________________.
 _______________________- molecules and proteins are “free floating” along the
phospholipid bilayer.
3 types of proteins found associated with cell membrane:
Channel Proteins- allow molecules or ions to enter the cell. They can be __________ or
___________
Receptor Proteins- ____________________ from outside the cell to inside the cell.
Marker Proteins- act as the ________________________of the cell.
Factors Affecting Transport
Molecules size and charge
 The cell membrane is _______________ to small neutral molecules, H2O, gases, and
lipids.
 The cell membrane is impermeable to _______________. Proteins are needed to move
these across the membrane.
Concentration gradient
 Molecules like to move from areas of ____________________ to areas of
____________________
Electrical gradient
 The inner membrane of the cell is slightly ________________ to the outer surface of the
cell.
 Therefor (+) charged molecules will be attracted______________ the cell.
Two Types of Transport:
___________________________ – requires no input of energy; Moves molecules
_____________ their concentration gradient.
Ex. _________________, __________________, ____________________
Diffusion:
Movement of molecules from an area of_____________ concentration to an area of
____________concentration.
When the concentration of molecules is the same throughout the space it occupies they are in a state
of _________________________
No Energy Needed
Osmosis:
The process by which _____________________ diffuse across a cell membrane from an area of
higher concentration to an area of lower concentration.
Water molecules can pass directly through the TINY spaces between phospholipid molecules
and don’t need to use channel proteins…
___________________- When the concentration of solute molecules outside the cell is lower
than the concentration inside the cell. Water molecules will have a net movement________ the
cell causing the cell to swell.
 The force that water molecules exert against the cell wall is called
______________________.
 If an animal cell takes in too much water it can burst. This is termed
_______________.
___________________- When the concentration of solute molecules outside the cell is higher
than the concentration in the cytosol. Water will have a net movement ______________the cell
causing the cell to shrivel.
 _____________________ is when osmotic pressure is lost due to water leaving the
cell. This is what causes plants to wilt.
_________________- When the concentration of solutes outside and inside the cell are equal.
There will be no net movement of water molecules.
No energy
needed
Facilitated Diffusion:
 This type of transport is for molecules that may not be soluble or are too large to pass
through the membrane pores.
 Requires ______________________ or _____________________ which move the
molecules down their concentration gradient.
 Protein channels are __________________ to one type of molecule
 Some are always open, others are gated and require ____________ to open and close.