The History of Cell Biology

An Introduction to the Cell

Robert Hooke - 1665

English Scientist

“I could exceedingly plainly perceive it to be all perforated and porous… consisting of a great many little boxes.”

Robert Hooke’s drawing of cork cells

In summary…

• In 1665, Robert Hooke used a microscope to view a thin slice of cork– He could see “a great many little boxes”– They reminded him of the rooms monks

lived in – “cells”– What he saw was the remains of dead

plant cells

Anton van Leeuwenhoek - 1673

Observed first living cells.

Anton van Leeuwenhoek’s Microscope

Letter from the English Royal Society:

20th of October, 1676

Dear Mr. Anthony van Leeuwenhoek,Your letter of October 10th has been received here with amusement. Your account of myriad 'little animals' seen swimming in rainwater, with the aid of your so-called 'microscope,' caused the members of the society considerable merriment when read at our most recent meeting…

… However, a vote having been taken among the members--accompanied I regret to inform you, by considerable giggling--it has been decided not to publish your communication in the Proceedings of this esteemed society. However, all here wish your 'little animals' health, prodigality and good husbandry by their ingenious 'discoverer.'

Hendrik OldenburgSecretary of the Royal Society, London

In summary…

• Anton van Leeuwenhoek saw the first living cells

• He called them “animalcules” and noted that they had horns– What he saw were protists and their

“horns” were cilia

• He wasn’t believed at first!

Theodor SchwannMatthias Schleiden Rudolf Virchow

Cell Theory

In summary…

– Matthias Schleiden and Theodor Schwann discovered plant and animal cells have nuclei

• They surmised that all living things must have cells

– In 1855, Rudolf Virchow reasoned cells come only from other cell

– And cell theory was born!

Cell Theory

• From there, scientists created a statement of cell theory– All living things are composed of one or

more cells.– Cells are the basic units of structure

and function in an organism.– Cells only come from the reproduction

of existing cells.

We’ve Come a Long Way!

• 1996 – Reaserachs in Scotland clone Dolly

• 2004 – Tissue engineering used to grow new skin and bone for transplant

Cellular Basis of Life

• Consist of organized parts• Obtain energy from surroundings• Perform chemical reactions• Change with time• Respond to the environment• Reproduce• Homeostasis• Share a common history

Diversity of Cells

An Introduction to the Cell

Cell Shape

In summary…

• Cells have a variety of shapes– “Diversity of shape reflects a diversity

of function.”– Shape has evolved to allow the cell to

perform its function effectively

Cell Size

How Big is a...?

Cell Size

• Volume of a Cube: Length x Width x Height• Surface Area of a Cube: Length x Width x Number of

Sides

• Time Out! Find the volume and surface area of 1 cm, 3 cm, and 6 cm cubes.

In summary…

• Most cells are microscopic– Most plant and animal cells are 10 – 50

micrometers (0.002 inches)– Some bacteria cells are only 0.2 micrometers

(0.000008 inches)

• Cells are limited by the ratio between their outer surface area and their volume– The cell’s surface needs to be able to allow

materials to enter or leave quickly enough to serve the cell’s need.

Eukaryotes and Prokaryotes

Animal Cell

Plant Cell

In summary…

• Prokaryotes– No membrane-bound nucleus– No membrane-bound organelles– They do contain DNA– These include bacteria

• Eukaryotes– Organisms made up of one or more

cells with:• Membrane-bound organelles• Nucleus

Colonial Organisms

Volvox

True Multicellularity

Organ Systems

In summary…

• Colonial organisms are genetically identical cells that live together in a connected group.

• Specialized cells need each other to survive– Cells Tissue Organ Organ System