Cell Discovery & Cell Theory

It all started with an invention…. microscope 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 ( ) ◦ Designed microscopes ◦ Discovered and documented the first “cells” in 1665  Named them after the cells in which a monk sleeps.

Robert Hooke ( ) Released book of detailed drawings and observations: Micrographia, 1665 Drawing of Flea 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.

Images from Micrographia

Antony van Leeuwenhoek ( ) A tradesman from Holland who became fascinated with Hooke’s book Discovered bacteria, 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 Mattias Schleiden 1838 Mattias Schleiden stated that all plant tissues consisted of cells Theodore Schwann 1839 Theodore Schwann stated that all animal tissues consisted of cells Each conjectured that there was a nucleus Rudolf Virchow 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. ◦T◦T hat is about the limit of a light microscope’s magnification without losing clarity (called Resolving Power). D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. ◦A◦A pprox. 100,000x magnification!! ◦C◦C ell 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 few limitations of electron microscopes Specimen must be placed in a vacuum and is typically coated with a conductive metal like gold. Consequently you can’t look at living specimens under electron microscopes. All images produced are black and white, so you can’t distinguish colors. Pictures are usually colored in digitally later.

Other Cool SEM pictures galleries/ /Creepy-crawlies-Amazing-Scanning- Electron-Microscope-pictures-of-insects-and-spiders.html

Carbon atoms bonded to hydrogen

Fruit fly with four eyes under an SEM

Vocabulary: Cell History Jansen Light Microscope Hooke Electron Microscope Van Leeuwenhoek Schleiden Schwann Virchow Cell Theory Resolving Power