The Cell TheoryThe Cell Theory

Some Random Cell FactsSome Random Cell Facts

The average human being is composed The average human being is composed of around 100 Trillion individual cells!!!of around 100 Trillion individual cells!!!

It would take as many as 50 cells to It would take as many as 50 cells to cover the area of a dot on the letter “cover the area of a dot on the letter “ii””

WOW!!!WOW!!!

Discovery of Cells- Robert Discovery of Cells- Robert HookeHooke

1665- English Scientist, Robert Hooke, 1665- English Scientist, Robert Hooke, “discovered” cells while looking at a thin slice “discovered” cells while looking at a thin slice of cork.of cork.

He described them as the “cells” that monks He described them as the “cells” that monks lived in.lived in.

He thought that cells only existed in plants and He thought that cells only existed in plants and fungifungi

Anton van LeuwenhoekAnton van Leuwenhoek

1673- Used a handmade microscope to 1673- Used a handmade microscope to observe pond scum & discovered single-celled observe pond scum & discovered single-celled organismsorganisms

He called them “animalcules”He called them “animalcules”

He also observed blood cells from fish, birds, He also observed blood cells from fish, birds, frogs, dogs, and humansfrogs, dogs, and humans

Therefore, it was known that cells are found in Therefore, it was known that cells are found in animals as well as plantsanimals as well as plants

150-200 Year Gap???150-200 Year Gap??? Between the Hooke/Leuwenhoek discoveries Between the Hooke/Leuwenhoek discoveries

and the mid 19and the mid 19thth century, very little cell century, very little cell advancements were made.advancements were made.

This is probably due to the widely accepted, This is probably due to the widely accepted, traditional belief in Spontaneous Generation.traditional belief in Spontaneous Generation.

Examples: Examples:

-Mice from dirty clothes/corn husks-Mice from dirty clothes/corn husks

-Maggots from rotting meat-Maggots from rotting meat

Robert BrownRobert Brown

Showed that the nucleus is a key part of Showed that the nucleus is a key part of each cell. Others had noticed the nucleus each cell. Others had noticed the nucleus but none thought it very important.but none thought it very important.

A Scottish biologistA Scottish biologist

SchleidenSchleiden

1838- German Botanist, Matthias 1838- German Botanist, Matthias Schleiden, concluded that all plant parts Schleiden, concluded that all plant parts are made of cellsare made of cells

He and Schwann are credited with He and Schwann are credited with advancing the first statement of the cell advancing the first statement of the cell theory.theory.

SchwannSchwann

1839- German physiologist & zoologist, 1839- German physiologist & zoologist, Theodor Schwann, who was a close friend Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues of Schleiden, stated that all animal tissues are composed of cells.are composed of cells.

VirchowVirchow

1858- Rudolf Virchow, German 1858- Rudolf Virchow, German physician, after extensive study of physician, after extensive study of cellular pathology, concluded that cells cellular pathology, concluded that cells must arise from preexisting cells.must arise from preexisting cells.

This means that This means that

cells can’t just becells can’t just be

createdcreated This is the 2This is the 2ndnd

part of the cell theory part of the cell theory

The Cell TheoryThe Cell Theory

The 3 Basic Components of the Cell Theory The 3 Basic Components of the Cell Theory were now complete:were now complete:

1. All organisms are composed of one or more 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39)cells. (Schleiden & Schwann)(1838-39)

2. The cell is the basic unit of life in all living 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39)things. (Schleiden & Schwann)(1838-39)

3. All cells are produced by the division of 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)preexisting cells. (Virchow)(1858)

Support of the Cell TheorySupport of the Cell Theory

Up until this time most people belived in Up until this time most people belived in Spontaneous Generation- the belief that life Spontaneous Generation- the belief that life could spring up from nonliving material.could spring up from nonliving material.

Louis Pasture’s experiments Louis Pasture’s experiments

conclusively disproved conclusively disproved

Spontaneous Generation and Spontaneous Generation and

supported the Cell Theorysupported the Cell Theory

Support of the Cell TheorySupport of the Cell Theory

1860’s German Scientist Walther Flemming 1860’s German Scientist Walther Flemming stained cells making them easier to see.stained cells making them easier to see.

This allowed him to discover how cells This allowed him to discover how cells reproduce.reproduce.

His discoveries supported His discoveries supported

the cell theory.the cell theory.

Modern Cell TheoryModern Cell Theory Modern Cell Theory contains 4 statements, in Modern Cell Theory contains 4 statements, in

addition to the original Cell Theory:addition to the original Cell Theory: The cell contains hereditary information(DNA) which The cell contains hereditary information(DNA) which

is passed on from cell to cell during cell division.is passed on from cell to cell during cell division. All cells are basically the same in chemical All cells are basically the same in chemical

composition and metabolic activities.composition and metabolic activities. All basic chemical & physiological functions are All basic chemical & physiological functions are

carried out inside the cells.(movement, carried out inside the cells.(movement, digestion,etc)digestion,etc)

Cell activity depends on the activities of sub-cellular Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, structures within the cell(organelles, nucleus, plasma membrane)plasma membrane)

How Has The Cell Theory Been How Has The Cell Theory Been Used?Used?

The basic discovered truths about cells, The basic discovered truths about cells, listed in the Cell Theory, are the basis listed in the Cell Theory, are the basis for things such as:for things such as: Disease/Health/Medical Research and Disease/Health/Medical Research and

Cures(AIDS, Cancer, Vaccines, Cloning, The Cures(AIDS, Cancer, Vaccines, Cloning, The Human Genome Project, Stem Cell Research, Human Genome Project, Stem Cell Research, etc.)etc.)

Some Parting ThoughtsSome Parting Thoughts

It is amazing to think that the cells that It is amazing to think that the cells that make up our bodies are just as alive as make up our bodies are just as alive as we are. Humans are just an intricately we are. Humans are just an intricately designed community of cells, which designed community of cells, which must work together to survivemust work together to survive