The Cell Theory

1. All living things are made up of one or more cells

2. Cells are the basic unit of structure and function

3. All cells come from pre-existing cells

4. Cells contain the hereditary information which is passed from cell to “daughter” cell during cell division

5. All cells are basically the same in chemical composition

The Cell Membrane: Gatekeeper of the Cell

How do the “approved” molecules get across the membrane?

The cell membrane regulates what molecules can and cannot go into the cell

Getting Across the MembraneHow do approved molecules get across the membrane?

By transport!

There are two types:

1.Passive transport (requires no energy)

a) Simple diffusionb) Facilitated diffusion

2. Active transport (requires energy)

DiffusionMovement of molecules from areas of high concentration to areas of low concentration

Movement continues until equilibrium is reached!Then there is no more NET movement of molecules.

Simple Diffusion (type of passive transport)

Movement of molecules across a membrane from areas of high concentration to areas of low concentration

Dialysis Bag Diffusion Experiment

Osmosis

Osmosis is the simple diffusion of water molecules!

Water moves from High water concentration to Low water concentration.

SO, water moves from Low solute concentration to High solute concentration

Hypertonic hyper = above

Hypotonic hypo = under

Isotonic iso = equal

When comparing the solute concentration between two solutions, you should use the following terms

Hypertonicity

Hypotonicity

Isotonicity

December 7, 2007

Bell-work:

You place a cell containing 0.5 grams of solutes in a solution containing 0.7 grams of solutes. The cell membrane is not permeable to the solutes.  

1. The cell is __________ to its environment (hypertonic/hypotonic/isotonic)

2. The environment is _______ to the cell. (hypertonic/hypotonic/isotonic)

3. Will the solutes diffuse? If yes, in which direction (in/out)?

4. Will the water diffuse? If yes, in which direction (in/out)?

Facilitated Diffusion (type of passive transport)

Special protein channels in the membrane allow for the transport of molecules into the cell from areas of high concentration to low concentration

Active Transport

Movement of substances AGAINST the concentration gradient

From areas of low concentration to areas of high concentration

REQUIRES ENERGY!

Two ways:

1. Protein Pumps

2. Carriers (vesicles)

1. Protein Pumps

2. VesiclesMembrane-bound organelles that carry products or wastes into, out of, or throughout the cell

Endocytosissubstances are brought into the cell

Think of it as cellulareating and drinking!

Amoeba “eating” some bacteria

Exocytosissubstances are released from the cell

Endo- or Exo- cytosis Video

Picture Overview

Is it a Prokaryote or a Eukaryote?

Plants

Bacteria

Protist

Animals