The Selectively Permeable Membrane Lab

Problem

What does selectively permeable mean?

Hypothesis

If iodine and starch are placed on opposite sides of a membrane, then the membrane will be selectively permeable by______________________________

Procedure

1. Measure 100 mL of iodine solution in a beaker.

2. Put 40 mL starch into a plastic bag which will act as a membrane.

3. Tie the bag closed with a string.

4. Place the bag into the beaker of iodine.

Initial Drawing of “Cell”

Homeostasis – Maintaining a BalanceCells must keep the proper

concentration of nutrients and water and eliminate wastes.

The cell membrane is selectively permeable.

Structure of the Plasma Membrane Lipid bilayer – two sheets of lipids

(phospholipids).– Found around the cell.– Embedded with proteins and

cholesterol molecules.

What’s a Phospholipid? It’s a pair of fatty acid chains and a

phosphate group attached to a glycerol backbone.

Getting into a cell (or out of it)

Passive transport – some particles are so small they can move into or out of a cell with no help and no energy need.

These particle move through diffusion

Diffusion

movement of particles from an area of high concentration to an area of low concentration.

Continues until an equilibrium is reached

Osmosis

Diffusion of water across a selectively permeable membrane.

Occurs until water is balanced on both sides of the membrane.

Membrane Proteins Facilitated diffusion – a type of

passive transport where proteins act as tunnels allowing larger particles to diffuse through with no energy.

Active transport – energy is needed to move particles.– Carrier proteins –change shape to

open and close passages across the membrane.