Transcript A View of the Cell

A View of the Cell
The Discovery of Cells
p.171-174
The History of the Cell Theory
• Before microscopes were
invented, people believed
that diseases were caused by
curses + supernatural
powers
• Microscopes opened the
world to microorganisms
• Microscopes enabled
scientists to study cells – the
basic unit of living things
Light Microscopes
• 1600s
– Anton van Leeuwenhoek
– Made the first microscope
• Compound Light Microscope
– Uses a series of lenses to
magnify objects
– Can magnify up to 1500x
Compound Light Microscope
The Cell Theory
•
Robert Hooke
– English scientist
– Studied cork – dead
cells of oak bark
– noticed repeated
geometric boxshaped structures –
called them CELLS
The Cell Theory
•
Several scientists extended
Hooke’s observations and
came up with important
conclusions
–
Schleiden
•
–
Botanist – concluded that plants
were made up of cells
Schwann
•
Zoologist – concluded that animals
were made up of cells
The Cell Theory
• The observations + conclusions of these
scientists are summarized as one
fundamental idea of modern biology – the
Cell Theory:
– All organisms are composed of one or more cells
– The cell is the basic unit of structure +
organization of organisms
– All cells come from preexisting cells
Electron Microscopes
• 1930s + 1940s – electron microscope was
developed
• Uses a beam of electrons to magnify
objects up to 500,000x the original size
• Specimens must be viewed in a vacuum
• Disadvantage?
– Cannot use living specimens
Two Types of EMs
• Scanning Electron Microscope (SEM)
– Scans surface features
– Creates a 3-D image
• Transmission Electron Microscope (TEM)
– Capable of seeing internal cell structures
Two Basic Cell Types
• All cells contain small, specialized
structures called organelles
– Many are surrounded by membranes
– Each has a specific function in the cell
Prokaryotes
• Cells that do not contain any membranebound organelles
• Many are unicellular organisms, such as
bacteria
Eukaryotes
• Cells that contain membrane-bound
organelles
• Many are multicellular but some may be
unicellular, such as yeasts or amoebas
Prokaryote vs. Eukaryote
• Organelles benefit eukaryotic cell
– Separates chemical reactions inside
the cell so many can happen at one
time
• Robert Brown+ Rudolf Virchow
– Observed a prominent structure
inside the eukaryotic cell that is
responsible for cell division
• Nucleus
– Central membrane bound
organelle that manages or
controls cellular functions
– AKA – “the brain of a cell”