Osmosis & Diffusion

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Slide 1

Cell Membranes

Osmosis and Diffusion

Slide 2

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

Slide 3

Phospholipid Bilayer

Slide 4

Fluid Mosaic Model

Slide 5

Blood-Brain Barrier

Allows some substances into the brain, but screens out toxins and bacteria

Substances allowed to cross include:

water, CO2, Glucose, O2, Amino Acids, Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier.

Slide 6

Solutions

Solutions are made of solute and a solvent

Solvent - the liquid into which the solute is poured and dissolved. We will use water as our solvent today.

Solute - substance that is dissolved or put into the solvent. Salt and sucrose are solutes.

Slide 7

Methods of Transport Across Membranes

1. Diffusion

2. Osmosis

3. Facilitated Diffusion

4. Active Transport

Slide 8

Methods of Transport Across Membranes

1. Diffusion -passive transport - no energy expended

2. Osmosis - Passive transport of water across membrane

3. Facilitated Diffusion - Use of proteins to carry polar molecules or ions across

4. Active Transport- requires energy to transport molecules against a concentration gradient – energy is in the form of ATP

Slide 9

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

Slide 10

Diffusion

Slide 11

Osmosis

Slide 12

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.