Cell Biology
Unit Three
Cell Membrane Characteristics & Function
Defines boundaries
Serve as location for functions
Facilitate and regulate movement of materials in & out of
the cell
Detect external signals
Provides mechanisms for cell to cell communication
Cell Membrane
Characteristics & Function
Cell Membrane Characteristics & Function
Cell Membrane Characteristics & Function
In facilitating and regulating the movement of materials in
& out of the cell, the membrane is said to be selectively
permeable
Plasma Membrane Structure
E face
Phospholipid
bilayer
P face
Plasma Membrane Structure
Membrane Protein Classes
Plasma Membrane Structure
Glycoprotein
s
Plasma Membrane Structure
Does not require energy from the cell
Substances move from an area of
high concentration to an area of
low concentration
Substances can move in both directions,
depending on the concentration gradient
Diffusion – the movement of a substance
from an area of high concentration to an
area of low concentration
Facilitated diffusion – same as above,
but with the help of membrane proteins
Osmosis – the diffusion of water
Does require energy from the cell
Substances move from an area of
low concentration to an area of
high concentration
Substances can move in only one direction,
against the concentration gradient
Sodium/Potassium pump – a membrane
protein that moves sodium out, while
moving potassium in
Endocytosis
* Phagocytosis
* Pinocytosis
Exocytosis
Osmosis
Solute – substance that is dissolved in a
medium (solvent)
Solvent – substance (usually liquid) that
dissolves a solute
Solution – mixture of solutes dissolved in
a solvent
Osmotic pressure is created by the
movement of water toward a higher
solute concentration
Osmosis
Diffusion
Semipermeable
membrane
Osmosis
Animal Cell Osmosis
Crenated
Plant Cell Osmosis
Turgor
Osmosis
Edema – the excess collection of
extracellular fluids due to high solute
concentration
Dehydration – the loss of extracellular
fluids due to various causes