Cell Theory & Membranes

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 Membrane How do approved molecules get across the membrane? By transport! There are two types:
Passive transport (requires no energy)‏
a) Simple diffusion
b) Facilitated diffusion
2. Active transport (requires energy)‏

Diffusion Movement 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. Vesicles Membrane-bound organelles that carry products or wastes into, out of, or throughout the cell

Endocytosis substances are brought into the cell Think of it as cellular eating and drinking! Amoeba “eating” some bacteria

Exocytosis substances are released from the cell

Endo- or Exo- cytosis Video

Picture Overview

Is it a Prokaryote or a Eukaryote?

Plants

Bacteria

Protist

Animals

Cell Theory & Membranes

by Stacy Baker on Jan 26, 2010

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Cell Theory & Membranes — Presentation Transcript