It’s a Cellular World
Unit 2: Cells
Chapter 7: Cell Structure and Function
Section 7-1 Life is Cellular
Text- pages -169-173
Vocabulary
Cell
Cell theory
Nucleus
Eukaryote
Prokaryote
Objectives
SWBAT explain how microscopes came
into use and the early observations that
were made by scientists.
 SWBAT describe the three steps of the Cell
Theory.
 SWBAT describe some modern microscope
techniques used to look at cells and their
parts.
 SWBAT explain how cells are classified.
 SWBAT describe the differences between
prokaryotes and eukaryotes.

Discovering the Cell



Mid 1600’s: scientists
began to use
microscopes to
observe living things.
1665: Robert Hooke
(England) compound
scope
1674: Anton van
Leeuwenhoek
(Holland) single lens
scope.
Cell Theory
Cell Theory states…
1) All living things are composed of cells.
2) Cells are the basic unit of structure
and function in living things.
3) New cells are produced from existing
cells.
Exploring the Cell Today
 Today’s
researchers use microscopes
and techniques that are much more
powerful than those of early
scientists.
 Examples:
fluorescent labeling, light
microscopes, 3-D imaging using
electron microscopes
Modern Techniques
 3-D
imaging
 Fluorescent
 Light
Labeling
Microscopes
Electron Microscopes
 SEM
: Scanning Electron Microscope
– Scanning a pencil-like beam of electrons
over the surface of an object. Produce a
3-d image
 TEM
: Transmission Electron Microscope
– The transmission electron microscope
(TEM) operates on the same basic
principles as the light microscope but
uses electrons instead of light.
 TEM
resource
– http://minerals.caltech.edu/Silica_Poly
morphs/index.html
– Pictures From The TEM
 SEM
resources
– scharfphoto.com: David Scharf: Home
– Pictures From The SEM
Classifying Cells



Variety of shapes and sizes.
Typical cell 5- 50 µm.
2 common characteristics:
1) Surrounded by barrier- cell membrane
2) At some point in the cell lifespan they
contain the molecule that carries
biological information- DNA.
How small is a micrometer
(um)?
1
micrometer (um) is one millionth
of a meter 1/1,000,000 m
 or 1 x 10-6
Cell Shapes
Classifying Cells cont’d

2 categories of cells- depend upon
whether they contain a nucleus.
– Eukaryotes: contain nuclei
– Prokaryotes: no nucleus

Nucleus: large membrane-enclosed
structure that contains cell’s genetic
material (nucleic acids) in the form of
DNA.
– Controls many of the cell’s activities.
Prokaryotes
 Smaller
and simpler than
eukaryotes.
 No nucleus.
 Some contain organelles.
 Carry out every activity associated
with living things.
– Grow, reproduce, respond to
environment, glide, and swim
– Example: Bacteria
Eukaryotes
 Larger
and more complex than
prokaryotes.
 Contain dozens of organelles.
 Highly specialized
 Contain nucleus
 Single celled or multi-cellular.
 Examples: plants, animals, fungi,
and protists.
Review Questions
 What
are the 3 statements that
make up the cell theory?
 What’s
the difference between
prokaryotes and eukaryotes?
 Do
bacterial cells contain nuclei?