Discovery of the Cell Robert Hooke (1665) English scientist looked at a thin slice of cork (oak cork) through a compound microscope observed tiny, hollow, room-like structures called these structures “cells” because they reminded him of the rooms that monks lived in only saw the outer walls (cell walls) because the cork cells were not alive

Discovery of the Cell Anton van Leeuwenhoek (mid-1600s) Dutch fabric merchant and amateur scientist looked at blood, rainwater, scrapings from teeth through a simple microscope (1 lens) observed living cells; called some “animalcules” some of the small “animalcules” are now called bacteria

Cell Theory Two scientists, Matthias Schleiden and Theodore Schwann (1830s) expanded upon Hooke’s observation of “cells” Their observations in plants and animal cells have been summarized as the Cell Theory

The Cell Theory 1. All organisms are composed of one or more cells 2. The cell is the basic unit of organization of organisms Unicellular organisms – made of one cell that must perform all life’s activities Multicellular organisms – made of more than one cell. Each cell performs most of the major functions of life 3. All cells come from preexisting cells Before the cell theory, people did not know where these cells came from. People learned that a cell divides to form two identical cells The ability of a cell to divide is the basis for all reproduction (sexual and asexual) Growth and repair of all multicellular organisms

Major Events in Cell Biology and Imaging

Development of Microscopes van Leeuwenhoek’s microscope was considered a simple light microscope because it used one lens and natural light Hooke’s microscope was compound because it used two lenses

Development of Microscopes In the 200 years after Hooke, compound light microscopes have improved to magnify objects 1500 times using two lenses and a beam of light Electron microscopes use a beam of electrons to magnify objects 500,000 times! This power allows us to see the structures on the surface and within the cell

Electron Microscopes Scanning Electron Microscope (SEM) Scans the surface of cells to show their three-dimensional shape Transmission Electron Microscopes (TEM) Sends electrons through a specimen to show the parts inside the cell Scanning Tunneling Microscope Uses electrons to investigate atoms on the surface of a molecule

Scanning Electron Microscope (SEM) Transmission Electron Microscopes (TEM) Scanning Tunneling Microscope

Compound Light Microscope Eyepiece Body Tube Revolving Nosepiece Arm Objective Lenses Stage Stage Clips Coarse Adjustment Diaphragm Fine Adjustment Light Source Base Source: http://www.biologycorner.com/microquiz/

Eyepiece – lens magnifies 10x Arm – Always carry with one hand on the arm and one on the base Stage – Supports the specimen slide Coarse Adjustment – moves stage up or down to bring specimen into focus Fine Adjustment – allows for precise focusing Base – supports the scope

Body Tube – supports the eyepiece and objectives Revolving Nosepiece – holds and rotates objective lenses ** Objective Lenses – magnify by 4x, 10x, 40x, or 100x Stage Clips – hold the specimen slide to the stage Diaphragm – controls the amount of light reaching the stage Light Source – provides the light that shines through the stage ** Since the eyepiece had a magnification of 10x, the total magnification when using the 4x objective lens would be 40x. When using the 10x objective lens, the total would be 100x. When using the 40x lens, the total would be 400x.

Microscope: The Tube that Changed the World