Download cells - Gainesville ISD

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
• both kinds have a plasma
membrane (outer covering)
• grouping is based on internal
structures called ORGANELLES
1. PROKARYOTES
• 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
FLUID MOSAIC MODEL
• Selective Permeability
• the membrane allows certain
molecules in while keeping other
molecules out
• allows the cell to maintain
homeostasis
• 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