NOTES: INTRODUCTION TO

CELLS

NOTES – CELL DISCOVERY

• History of Cells

• Robert Hooke: uses microscope to look at cork - called the chambers he saw “cells”

• Anton van Leeuwenhoek: first to find microscopic living organisms

• Mattias Schleiden: all plants are made of cells

• Theodor Schwann: all animals are made of cells

• Rudolf Virchow: all cells come from pre-existing cells

• CELL THEORY: 3 parts 1. All organisms are composed of one or more cells

2. The cell is the basic unit of structure and organization of living organisms

3. All cells come from pre-existing cells

• CELL TYPES: 2 basic kinds

1. PROKARYOTES

• grouping is based on internal structures called ORGANELLES

• both kinds have a plasma membrane (outer covering)

• do not have internal organelles – only some DNA, ribosomes floating in cytoplasm – EX: bacteria

2. Eukaryotes • has internal organelles surrounded by a membrane

• EX: typical animal or plant cell

Eukaryote Prokaryote

THE PLASMA MEMBRANE

• Plasma Membrane (CELL MEMBRANE)

• boundary between the cell and its environment

• 2 Functions 1. Separate & protect the cell from its environment

2. regulates what enters & leaves the cell

• the process of maintaining the cells environment is called: HOMEOSTASIS

• Selective Permeability

• the membrane allows certain molecules in while keeping other molecules out

• allows the cell to maintain homeostasis

FLUID MOSAIC MODEL

• Cell Membrane Structure

• Most molecules of the cell membrane are lipids

• When a phosphate group replaces a fatty acid a PHOSPHOLIPID forms

• Each phospholipid has a head with 2 tails

• Head – attracts water• Tail – repels water

• membrane is called a PHOSPHOLIPID BILAYER

• phosphate + lipid keeps water out & in

• only certain molecules are allowed in or out

• The CELL WALL is the outer boundary of a plant cell

• the cell wall is outside the cell membrane in plants

• FUNCTIONS: support & protection

• stiff/rigid structure