Cell Membranes Osmosis and Diffusion

1
Cell MembranesOsmosis and Diffusion
2
Functions of Membranes

• 1. Protect cell
• 2. Control incoming and outgoing substances
• 3. Maintain concentrations of various substances
• 4. Selectively permeable - allows some molecules
  in, others are kept out

3
Define selectively permeable membrane

• A membrane that allows only certain materials to
  cross it
• Materials pass through pores in the membrane

4
Phospholipid Bilayer
5
Fluid Mosaic Model
6
Methods of Transport Across Membranes

• 1. Diffusion passive transport
• 2. Osmosis passive transport
• 3. Active Transport requires energy to transport
  molecules against a concentration gradient
  energy is in the form of ATP

7
Solutions

• Solutions are made of solute and a solvent
• Solvent - the liquid into which the solute is
  poured and dissolved. Water is a universal
  solvent.
• Solute - substance that is dissolved or put into
  the solvent. Salt and sucrose are solutes.

8
Define Diffusion

• The movement of molecules from an area in which
  they are highly concentrated to an area in which
  they are less concentrated.
• Movement from one side of a membrane to another,
  un-facilitated no energy used

9
Draw a diagram of an example of diffusion
10
Diffusion
11
Define osmosis

• The diffusion of water across a selectively
  permeable membrane.
• Passive transport no energy used

12
Define osmosis
http//www.usd.edu/bgoodman/Osmos.htm
13
(No Transcript)
14
(No Transcript)
15
Why are osmosis diffusion important?

• All living things have certain requirements they
  must satisfy in order to remain alive maintain
  homeostasis
• These include exchanging gases (usually CO2 and
  O2), taking in water, minerals, and food, and
  eliminating wastes.
• These tasks happen at the cellular level.
• Molecules move through the cell membrane by
  diffusion

16
Why are osmosis diffusion important?

• This membrane is a complex structure that is
  responsible for separating the contents of the
  cell from its surroundings, for controlling the
  movement of materials into and out of the cell,
  and for interacting with the environment
  surrounding the cell.