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Chapter 2, Section 3

Discovering Cells

+An Overview of Cells

Cells: the basic units of structure and function in

living things

Cells and StructureHow cells are put together and the shape that forms

Cells and FunctionObtaining oxygen, getting rid of wastes, obtaining

food, and growing

+First Observations of Cells 1590

The invention of the microscope made it possible for people to discover and learn about cells

Microscope: an instrument that makes small objects look larger SIMPLE MICROSCOPE: one

lens COMPOUND MICROSCOPE:

more than one lens

+Robert Hooke

One of the first people to observe cells

Built his own compound microscope

Used this microscope to observe thin slice of cork Looked like tiny rectangular rooms, called

them cells meaning “small rooms”

+Anton van Leeuwenhoek

About the same time as Hooke

Built a simple microscope

Used this microscope to observe lake water, scrapings from teeth and gums, and water from rain gutters He noticed that many of the things

he observed were ONE-CELLED

He called the moving organisms he saw ANIMALCULES (“little animals”)

+Development of the Cell TheoryThree scientists worked together…

Schleiden Concluded all plants are made of cells

Schwann Concluded that all animals are also made of cells

THEREFORE, all living things are made up of cells

Virchow New cells are formed only

from cells that already exist “All cells come from cells”

+The Cell Theory

The cell theory is a widely accepted explanation of the relationship between cells and living things

1. All living things are composed of cells

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

3. All cells are produced from other cells

+ Magnification and Lenses

Lenses in light microscopes magnify an object by BENDING the light that passes through them

Convex lens: magnifying glass and hand lenses Middle of lens is thicker Outside of lens is thinner

+Compound Microscope Magnification

Lenses of a LIGHT microscope… Light passes through specimen Then through two lenses

1st lens near specimen magnifies object 2nd lens near the eye further enlarges object

Example: One lens makes an object 10 times larger,

second lens makes an object 40 times larger TOTAL: 10 X 40 = 400

+Resolution

Being able to clearly distinguish the individual parts of an object

Or…sharpness of an image

+Electron Microscope

Electron microscope uses a beam of electrons instead of light to produce a magnified image

The resolution is much better than the resolution of a light microscope