Introduction to Cells

The cell theory

– All organisms are made of cells

The cell theory

– All cells arise from preexisting cells

The cell theory

– The cell is the basic unit of life • Even unicellular organisms carry out all

the functions of life

Evidence for the Cell Theory

Read this short summary of evidence for the

cell theory.

Organization is basically similar in all cells

• All cells have a cell membrane which is a selective barrier – Lets some materials in /

out of the cell

– Prevents other materials from coming in / out

Organization is basically similar in all cells

– Internally, all cells contain • Cytoplasm

• Ribosomes

• A region that contains DNA

Viruses are not cells

• Viruses are pieces of DNA or RNA surrounded by a protein coat.

There are two main types of cells: Prokaryotic Bacteria Archaea

Eukaryotic Protist Plants Fungi Animals

Figure 1.11 Three domains of life

Bacteria have prokaryotic cells:

• No true nucleus

• Unicellular

• 2 types: – Eubacteria (true

bacteria)

– Archaea bacteria

Protists, plants, fungi, and animals

have eukaryotic cells.

Eukaryotic cells contain organelles

• An organelle is a discrete structure within a cell that has a specific function

• Organelles are covered by their own membrane.

Cells work together in organisms that contain more than one cell

• A tissue is an integrated group of cells that

have a common structure and function.

TISSUE

• An organ is a group of different types of tissues that performs a specialized function

ORGAN

• An organ system is a group of organs that specialize in a certain function together.

Each level of biological organization

exhibits emergent properties (click link)

Ex.

Capillaries

transport

blood (property not

exhibited by

individual

endothelial

cells).

In multicellular organisms, cells become specialized.

All the cells contain all the genes, but they do not use all of them.

The cells of a multicellular organism differentiate to carry out specialized functions by only expressing some of their genes.

Cells in multicellular organisms differentiate (click link to read what this means!)