CELLS

The Cell Overview
Early Contributions
Robert Hooke - The first person to see cells, he was looking at cork and noted that he saw "a great many boxes. (1665)
Anton van Leeuwenhock - Observed living cells in pond water, which he called "animalcules" (1673)
Theodore Schwann - zoologist who observed that the tissues of animals had cells (1839)
Mattias Schleiden - botonist, observed that the tissues of plants contained cells ( 1845)
Rudolf Virchow - also reported that every living thing is made of up vital units, known as cells. He also predicted that cells come from other cells. (1850 )

The Cell Theory
1. Every living organism is made of one or more cellss.
2. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions.
3. All cells arise from pre-existing cells.

*Why is the Cell Theory called a Theory and not a Fact?
Cell Features

Ribosomes - make protein for use by the organism
Cytoplasm - jelly-like goo on the inside of the cell
DNA - genetic material
Cytoskeleton - the internal framework of the cell
Cell membrane - outer boundary of the cell, some stuff can cross the cell membrane.

Types of Cells
Prokaryotic Cells
Prokaryotes are very simple cells, probably first to inhabit the earth.
Prokaryotic cells do not contain a membrane bound nucleus.
Bacteria are prokaryotes.
DNA of bacteria is circular.
The word "prokaryote" means "before the nucleus"

Other features found in some bacteria:

Flagella - used for movement
Pilus - small hairlike structures used for attaching to other cells
Capsule - tough outer layer that protects bacteria, often associated with harmful bacteria
Eukaryotic Cells
Eukaryotic cells are more advanced cells.
These cells are found in plants, animals, and protists (small unicellular "animalcules").


The eukaryotic cell is composed of 4 main parts:
cell membrane - outer boundary of the cell
cytoplasm - jelly-like fluid interior of the cell
nucleus - the "control center" of the cell, contains the cell's DNA (chromosomes)
organelles - "little organs" that carry out cell functions

ORGANELLES WITH DNA
* The Mitochondria and Chloroplasts have their own DNA
* ENDOSYMBIOSIS THEORY - eukaryotic cells evolved from the engulfing of bacteria cells, thus creating additional cell parts

CELL MEMBRANE
* Function: to regulate what comes into the cell and what goes out
* Composed of a double layer of phospholipids and proteins