Introduction To Cells* All living things are made up of cells that have similar basic structures.

Discovery of Cells• Microscope observations of organisms

led to the discovery of the basic characteristics common to living things.

• Robert Hooke – English Scientist in 1665:

* Looked at slices of cork at 30x their normal size.

* The small boxes reminded him of small rooms where monks lived, so he called them “cells.”

• Anton Van Leeuwenhoek – Dutch Scientist in 1675:

* Used a more powerful microscope to magnify objects 300x

* The first to observe single-celled organisms in pond water that he named “animalcules.”

* The “Father of Microscopy”

Leeuwenhoek’s Animalcules

Robert Brown

• English Scientist 1830• Built an improved

microscope• Used it to observe

cells he had stained with various reagents.

• First to observe the nucleus of cells.

Robert Brown’s Microscope and Cells with a Nucleus

• Matthias Schleiden – German Botonist in 1838: Studied hundreds of plants.

* Concluded that cells make up every part of a plant.

• Theodor Schwann – German Zoologist in 1839: Studied hundreds of animals.

* Discovered that all animals are made up of cells

• Rudolph Virchow – German Physician in 1858: Looked at cells dividing.

* Proposed that cells come only from pre-existing cells.

The Cell Theory

The observations of Schleiden, Schwann, and Virchow formed the “cell theory” which states:

1. All living things are made up of one or

more cells.

2. Cells are the basic units of structure and function in organisms.

3. All cells arise from pre-existing cells.

Basic Cell Facts:• A cell’s shape reflects its function• There are at least 200 types• The human body is made up of about 100

trillion cells

hair cells skin cells

2 Basic Cell Types1. Prokaryotes: “pro”=before,

“karyo”= nucleus* Single-celled organism (ex. bacteria)

* No nucleus or other membrane-bound organelles

* For millions of

years, the only

organisms on earth

2. Eukaryotes: “eu”=true; “karyo” = nucleus* Have a membrane–bound nucleus that houses the DNA

* Contain membrane-bound organelles with specific functions.