Unit 4: Cells

Learning Goal A: Describe the cell theory and how it relates to

the nature of science.

Cell History

History of the Cell

Robert Hooke (1665) Used an early compound microscope he had built to

look at a thin slice of cork (plant material).• Looked like tiny, empty chambers.

• Called them “cells”

History of The Cell

Anton van Leeuwenhoek (1674) Observed pond water under a microscope. Observed tiny living organism.

• Called them animalcules

History of The Cell

Matthias Schleiden (1838) A German Botanist Concluded that all plants are made up of cells.

Theodore Schwann (1839) A German Biologist Concluded that all animals are made up of cells.

History of The Cell

Rudolph Virchow (1855) A German Physicist Proposed that all cells come from preexisting cells.

Cell Theory

The cell is the fundamental unit of structure and function in living things.

All organisms are made up of one or more cells. Cells arise from other cells through cellular division. Cells carry DNA passed to daughter cells during cellular

division. All cells are essentially the same in chemical

composition. Energy flow (metabolism and biochemistry) occurs

within cells.

Cell Exploration

14th century – The art of grinding lenses is developed in Italy and spectacles are made to improve eyesight. 

1590 – Dutch lens grinders Hans and Zacharias Janssen make the first microscope by placing two lenses in a tube. 

18th century – Several technical innovations make microscopes better and easier to handle, which leads to microscopy becoming more and more popular among scientists.

Cell Explorationo1878 – Ernst Abbe formulates a mathematical theory correlating resolution to the wavelength of light. Abbes formula make calculations of maximum resolution in microscopes possible. 

o1903 – Richard Zsigmondy develops the ultramicroscope and is able to study objects below the wavelength of light.  o1932 – Frits Zernike invents the phase-contrast microscope that allows the study of colorless and transparent biological materials.

Cell Exploration

 1938 – Ernst Ruska develops the electron microscope. The ability to use electrons in microscopy greatly improves the resolution and greatly expands the borders of exploration. 1981 – Gerd Binnig and Heinrich Rohrer invent the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level.

Cell Exploration

Confocal Light Microscopy Scans cells with a laser beam, makes it

possible to build three-dimensional images of cells and their parts.

Cell Exploration

Electron Microscopes Makes it possible to see details as

much as 1000 times smaller than

those visible in light. Sample being observed are preserved and the water

is removed before they are observed. Only nonliving samples can be

observed.

Cell Explorations

TEM (Transmission Electron Microscope) Uses a beam of electrons to explore cell structures

and large protein molecules. Because electrons can only pas through thin samples,

cells and tissues must be cut first. SEM (Scanning Electron Microscope)

A pencil like beam of electrons is scanned over the surface of a specimen.

Produces three-dimensional images of the cell. Scanning Probe Microscopes

Produce images by tracing the surface of samples. Made it possible to observe single atoms.

Cell Explorations