CELLS

Cell DiscoveryHow Did We Find Cells???

It took a long time for people to discover cells and figure out what they were all about. We

needed sophisticated equipment (microscopes!) to be able to see cells.

The First MicroscopesThe early simple "microscopes“

were only magnifying glasses that had one power, usually

about 6x - 10x.

One thing that was very common and interesting to look at, were fleas so these early magnifiers called "flea

glasses".

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Antony Van Leeuwenhoek

(1632-1723)This Dutch scientist, became the first man to

make and use a real microscope.

He would grind a small glass ball into a lens with a magnification of 270x, the finest known at

that time (other microscopes of the time were lucky to achieve 50x magnification).

Leeuwenhoek, with his new improved microscope, was able to see things that no man had ever seen before like bacteria, yeast, blood cells and many tiny animals swimming in a drop

of water. People did not realize that magnification might reveal structures that had never been seen before - the idea that all life might be made up of tiny components unseen by the unaided eye was simply not even

considered.

Hooke was an English scientist who improved Leeuwenhoek ‘s microscope. He looked at cork through a compound microscope and observed tiny room-like

structures that reminded him of the "cells" that monks lived in.  Therefore these structures became known as cells. 

Robert Hooke (1665) 

Matthias Schleiden (1838)

Schleiden was German Botanist the viewed plants under a microscope and discovered that plant are made of cells. He is considered to be

one of the co-founders of cell theory.

Theodor Schwann (1839)

Schwann was a German Biologist  who viewed animal parts under a microscope and discovered that animals were also made up of cells. He extended Schleiden's cell theory about plants to animals, stating that ALL living things are composed of cells.

Rudolph Virchow (1855)

Virchow was a German physician that stated that all living cells come only from other living cells.

Watch this!

Cell Theory

Every thing we now know about cells was combined and called the

“cell theory”.

Cell Theory says that….

1. All living things are made of cells.

2. Cells are like the building blocks of all living things.

3. New cells are only made from existing cells.

Cells are the basic units of structure and function in all living things

Cells come in all shapes and sizes!

There Are Two Types of Cells

Prokaryote Cells

And

Eukaryote Cells

Examples of the two types of cells are…

Eukaryotes

Animal Plant

These are two distinct types of cells with STRUCTURAL

differences.Cell Membrane

DNA

Nucleus

Cytoplasm

Prokaryote Cell

A simple single celled organism.

Traits of Prokaryotes: (pro-care-ee-ohts)

• They do not have a nucleus, and their genetic material is not stored in the nucleus.

• They have only a few organelles.

• They are less complicated that eukaryotes.

• All bacteria are prokaryotes. Archaebacteria are the oldest life forms and can only survive in very harsh conditions. Eubacteria are common and found every where… even in you!

Bacteria may be small but they are powerful!

During the 14th century, 25% or ¼ of Europe was killed by a bacteria called the Bubonic Plague,

also called Black Death. This bacteria was spread through fleas and rodents.

But at the same time we need bacteria to live!

1. Bacteria are decomposers and without them all other organisms would not be able to survive.

2. We use bacteria in our digestive system to help digest our food. There are approximately ten times as many bacterial cells as human cells in the human body!

3. We could not make cheese or yogurt without bacteria.

Eukaryote Cell

A more complex cell.

Traits of Eukaryotes: (you-care-ee-othts)

• They all have a nucleus where the genetic material of the cell is stored.

• They have many organelles and are more complex then prokaryotic cells.

• They can be single celled (just one cell) or can make

up more complex multi-cellular organisms.

• All plants, animals, fungi, and protists are eukaryotic cells.

Animals

PlantsProtist (single celled organisms)

Fungi

All made of Eukaryotic cells!

Think – Pair - Share

What do you think is the main difference

between a prokaryotic cell and a eukaryotic

cell?

The nucleus!PROkaryotic cells have NO

nucleus &

EUKARYotic cells DO CARRY a nucleus.

If there is time watch this introduction on cells!