Introduction to CellsIntroduction to CellsBiology A/CellsBiology A/Cells

The DiscoveryThe Discovery

• Cells were first discovered in 1665 when Cells were first discovered in 1665 when Robert Hooke observed a slice of cork under a Robert Hooke observed a slice of cork under a microscope.microscope.

• Hooke thought the small divisions looked like Hooke thought the small divisions looked like the monastery cells that monks lived in.the monastery cells that monks lived in.

The DiscoveryThe Discovery

• Anton van Leeuwenhoek was the first to Anton van Leeuwenhoek was the first to observe observe micro-organismsmicro-organisms in 1674, when he in 1674, when he observed a drop of water under a microscope.observed a drop of water under a microscope.

The Discovery The Discovery Continues…Continues…

• The combined work of a number of other The combined work of a number of other scientists finally led to the development of the scientists finally led to the development of the cell theory.cell theory.

The Cell TheoryThe Cell Theory

• All living things are made of cells.All living things are made of cells.

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

• New cells are only produced by other cells.New cells are only produced by other cells.

Micro-organismsMicro-organisms

• We will discuss 3 main types of micro-We will discuss 3 main types of micro-organisms:organisms:

1. Viruses1. Viruses

2. Bacteria2. Bacteria

3. Protists 3. Protists

BacteriaBacteria

• Bacteria are microscopic, single-celled Bacteria are microscopic, single-celled organisms.organisms.

• Bacteria are Bacteria are prokaryotesprokaryotes which means that which means that their DNA is not contained inside the their DNA is not contained inside the protective coating of a nucleus.protective coating of a nucleus.

VirusesViruses

• Viruses are the simplest and smallest micro-Viruses are the simplest and smallest micro-organisms.organisms.

• They contain a small amount of DNA (genetic They contain a small amount of DNA (genetic material) and a protective coat called a material) and a protective coat called a capsid.capsid.

• Viruses reproduce by attaching to another cell Viruses reproduce by attaching to another cell and overriding normal cell functioning so that and overriding normal cell functioning so that the cell produces new viruses.the cell produces new viruses.

2 Categories of Cells2 Categories of Cells

Prokaryotic CellsProkaryotic Cells Eukaryotic Eukaryotic CellsCells

Prokaryotic CellsProkaryotic Cells

• Do not contain a nucleusDo not contain a nucleus

• Are smaller and simpler than eukaryotic cellsAre smaller and simpler than eukaryotic cells

• Example: BacteriaExample: Bacteria

Eukaryotic CellsEukaryotic Cells

• Have a nucleusHave a nucleus

• Are larger and more complex than prokaryotic Are larger and more complex than prokaryotic cellscells

• Contain specialized structures called Contain specialized structures called organellesorganelles

• Examples: Plant cellsExamples: Plant cells

Animal cellsAnimal cells

ProtistsProtists

• Protists are generally larger than viruses and Protists are generally larger than viruses and bacteria, but they are still microscopic.bacteria, but they are still microscopic.

• Protists are Protists are eukaryotes, eukaryotes, which means their which means their DNA is contained in a protective nucleus.DNA is contained in a protective nucleus.