What is a cell?

An introduction to the cellSection 7.1

A Cell Is….• the basic unit of life• the smallest division of an organism

that is still considered to be alive• a cell has all 5 characteristics of life;

produce offspring, growth & development, orderly structure, adapt to changes in environment, and adapt and evolve

• a cell’s basic parts are cytoplasm, DNA/RNA, and plasma membrane

• Some also contain organelles—a membrane bound structure that has a particular function in the cell

• Hierarchy—cells from tissues—tissues form organs—organs form organ systems—organ systems form organism

HierarchyCELLS

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TISSUES

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ORGANS

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ORGAN SYSTEM

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ORGANISM

Discovery• The invention of the microscope

lead to the discovery of the cell.• Anton van Leeuwenhoek invented

the first light microscope

• Robert Hooke discovered the cell using a compound light microscope.

Microscopes •Compound Light Microscope:

uses a series of lenses to magnify objects up to 1500 times.

•Electron Microscope: uses a beam of electrons to magnify up to 500,000 times

• Types of Electron Microscopes:–Scanning Electron Microscope: shows a 3-D shape

–Transmission Electron Microscope: shows the structures on the inside of the cell

THE CELL THEORY

• The cell is the basic unit of life• All organisms are composed of

one or more cells• Cells come from pre-existing

cells• Contributors to the cell theory:

Hooke, Schliden, and Schwann.

Types of Cells• Prokaryotic—has no membrane

bound organelles

• Eukaryotic—has membrane bound organelles

Types of Cells

•Nucleus: organelle in eukaryotic cells that controls the cellular functions

•Robert Brown: discovered the nucleus