Cell Discovery & Cell Theory

It all started with an invention….

The first microscope– Zacharias Jansen, 1595,

Middleburg, Holland– It launched great leaps

in Astronomy and Biology.

– Some of the first great observations with it were made by…

Robert Hooke (1635-1703)

– Designed microscopes– Discovered and documented

the first “cells” in 1665• Named them after the cells in

which a monk sleeps.

From: http://www.ucmp.berkeley.edu/history/hooke.html

Robert Hooke (1635-1703)

Hooke’s drawing of a flea from: http://www.rod.beavon.clara.net/micro1.htm

From the Museum of Natural History website:http://www.natmedmuse.afip.org/explore/micro/hooke.html http://micro.magnet.fsu.edu/optics/timeline/people/hooke.html

Released book of detailed drawings and observations: Micrographia, 1665

Hooke had a life-long rivalry with Sir Isaac Newton. Newton worked hard to destroy his reputation during and after his death. Much of Hooke’s work was destroyed – even his gravesite is still unknown.

Antony van Leeuwenhoek (1632-1723)

A tradesman from Holland who became fascinated with Hooke’s book Discovered bacteria, free-living protists, sperm cells, blood cells, nematodes, etc. Became an expert lens grinder and made

over 500 simple microscopes Acute eyesight and lens grinding skill let him

build microscopes that were capable of 200X magnification

Cell Theory

1838 Mattias Schleiden stated that all plant tissues consisted of cells

1839 Theodore Schwann stated that all animal tissues consisted of cells

Each conjectured that there was a nucleus 1858 Rudolf Virchow combined the two ideas

and added that all cells come from pre-existing cells, formulating the Cell Theory

Rudolf Virchow 1858

Cell Theory All living things are

composed of one or more cells

In organisms, cells are the basic units of structure and function.

All cells are produced only from existing cells.

Modern Microscopes Some of the light microscopes here are capable of

1000x magnification.– That is about the limit of a light microscope’s magnification

without losing clarity (called Resolving Power).• Due to the width of visible light’s wavelength

The electron microscope was introduced in the 1950s and uses the wavelength of electrons to increase the resolving power by 100x. – Approx. 100,000x magnification!!– Cell Biology advanced rapidly as cellular organelles were

clearly seen for the first time.

Resolving Power

Transmission Electron Microscope (TEM) magnifies a slice of a sample. (Rabbit trachea cilia)

Scanning Electron Microscope (SEM) shows 3D image of the Rabbit trachea cilia

Modern Microscopes

A modern TEM

Fruit fly with four eyes under an SEM