cell membrane osmosis and diffusion, Study notes of Biology

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Cell Membranes

Osmosis and Diffusion

Functions of Membranes

1. Protect cell

2. Control incoming and outgoing substances

3. Maintain ion concentrations of various

substances

4. Selectively permeable - allows some

molecules in, others are kept out

5. ALL THIS MAINTAINS HOMEOSTASIS

(internal balance)

Fluid Mosaic Model

Methods of Transport Across

Membranes

1. Diffusion

2. Osmosis

3. Facilitated Diffusion

4. Active Transport

Types of Cellular Transport

• Passive Transport

cell doesn’t use energy

1. Diffusion
2. Facilitated Diffusion
3. Osmosis

• Active Transport

cell does use energy

1. Protein Pumps
2. Endocytosis
3. Exocytosis high low This is gonna be hard work!! high low Weeee!! !

• Animations of Active Transport & Passive Transport

Diffusion

• Movement of molecules from an area of

high concentration to an area of low

concentration.

• Movement from one side of a membrane

to another, un-facilitated

Passive Transport: Diffusion

Diffusion : random movement of

particles from an area of high

concentration to an area of low

concentration.

( High to Low )

• Diffusion continues until all molecules are evenly spaced ( equilibrium is reached)- Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm Simple Diffusion Animation

• Osmosis : diffusion of

water through a

selectively permeable

membrane

• Water moves from high to

low concentrations

• Water moves freely through pores.
• Solute (green) too large to move across. Osmosis animation Passive Transport: Osmosis

Tonicity is a relative term

• Hypotonic Solution - One solution has a

lower concentration of solute than

another.

• Hypertonic Solution - one solution has a

higher concentration of solute than

another.

• Isotonic Solution - both solutions have

same concentrations of solute.

Plant and Animal Cells put into

various solutions

Hypertonic Solution Hypertonic : The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) Result: Water moves from inside the cell into the solution: Cell shrinks ( Plasmolysis )!

• Osmosis Animations for isotonic, hypertonic, and hypotonic solutions shrinks

Isotonic Solution Isotonic : The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

• Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Facilitated diffusion : diffusion of specific particles through transport proteins found in the membrane a. Transport Proteins are specific – they “select” only certain molecules to cross the membrane b. Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport : Facilitated Diffusion Carrier Protein

A B

High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel Passive Transport: Facilitated Diffusion Go to Section: Transport Protein Through a → Cellular Transport From a-

High

Low

• Channel Proteins animations