Chapter 8

8-1: Cell Membrane

Homeostasis
 Homeostasis – the maintenance of stable internal conditions in a changing environment
 Examples

Regulation of body temperature

Control of blood glucose levels (insulin)

Lipid Bilayer
 The cell membrane is consisted of two layers

Phospholipid bilayer



Phospho- phosphate group
Lipid – fatty acids
Bi – two

Lipid Bilayer
 The two layers are made of two components


Hydrophilic heads


Water lovers
Found outside the membrane
Hydrophobic tails


Water haters
Found inside the membrane

8-2: Cellular Transport

 Passive Transport – does not require energy for movement across a membrane

Simple Diffusion


Facilitated Diffusion
Osmosis



Hypertonic
Hypotonic
Isotonic
 Active Transport – requires energy for movement across a membrane

Sodium-potassium pump


Endocytosis
Exocytosis

Simple Diffusion


Simple diffusion – The movement of molecules from an area of higher concentration to a lower concentration
Example

Perfume or air freshener

Simple Diffusion
 Concentration gradient
– a difference in the concentration of a substance across a distance

Solute




Solute – materials passing through membranes
Solvent – the fluid where materials are found
Solution = Solute +
Solvent
Selectively permeable – a property of cell membranes that allows only certain things to cross but not enter
Solvent - water

Facilitated Diffusion
 The movement of molecules across a membrane through special proteins in the membrane
Macromolecule

Facilitated Diffusion


Channel proteins –
Ions, sugars, and amino acids can diffuse through the cell membrane
Carrier proteins –
Transport substances that fit within their binding site

This binding causes the protein to change shape

Osmosis


The movement of water across a membrane
Hypotonic

“Hippo” meaning big


More water enter cells than leave cells
Cell swells

Osmosis


Hypertonic


More water leave cells than enter cells
Cell shrinks
Isotonic

Equal amount of water enter and leave cells
 Cell size remains the same

Hypotonic Hypertonic

Active Transport
 Pumps
 Sodium-potassium pump
– a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Active Transport


Endocytosis – used by a cell to take in a large particle
Vesicle – a sac used to transport materials within a cell

Active Transport
 Exocytosis – used to release materials out of the cell