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Cells
Chapter 6 Notes
What does the word ‘Cell’
Mean?
 The
word cell is derived from the Latin
word 'cellula' which means small
compartment.
A Famous Man in Science –
Robert Hooke
 In
1663 an English scientist, Robert Hooke,
discovered cells in a piece of cork, which
he examined under his primitive
microscope.
 Hooke
only observed cell walls because
cork cells are dead and without
cytoplasmic contents.
 Hooke
drew the cells he saw and also
coined the word CELL.
Anton van Leeuwenhoek
 Today,
he is known as
the “Father of
Microbiology” and
discovered bacteria

Used his own (single
lens) monocular
microscopes and was
the first person to
observe bacteria and
protozoa
Anton van Leeuwenhoek
 Built
microscopes that magnified over 200
times, with clearer and brighter images
than any of his colleagues at that time.
Cell Theory
 The
CELL THEORY, or cell doctrine, states that
all organisms are composed of similar units
of organization, called cells.
 The
concept was formally articulated in
1839 by Schleiden & Schwann and has
remained as the foundation of modern
biology.
Cell Theory Components

1.
2.
3.
4.
5.
6.
There are 6 Components to Cell Theory:
All known living things are made up of cells.
The cell is structural & functional unit of all living
things.
All cells come from pre-existing cells by division.
(Spontaneous Generation does not occur).
Cells contain hereditary information which is
passed from cell to cell during cell division.
All cells are basically the same in chemical
composition.
All energy flow (metabolism & biochemistry) of life
occurs within cells.
Two Major Classes of Cells
1.
2.
Prokaryotic Cell

Lacks a nucleus and most other organelles.

Bacteria and another group of organisms called
the archaea are prokaryotic cells. Prokaryotic
organisms appear earliest in Earth's fossil record.
Eukaryotic Cell

Has a nucleus surrounded by its own membrane,
and has other internal organelles bounded by
membranes.

Protists, fungi, plants, and animals consist of
eukaryotic cells. Organisms with eukaryotic cells
appeared later in Earth's history.
Prokaryotic Cells
A
bacterium is an example of a prokaryotic cell
(pro means "earlier than").
 Prokaryotic
cells are much simpler in structure
 They
do not have a true nucleus or membrane
bound organelles that a eukaryotic cell would
have.
 The
DNA in a prokaryotic cell is concentrated in
an area called the nucleoid region:

This is not separated from the rest of the cell by a
membrane. ONLY EUKARYOTIC CELLS HAVE
MEMBRANE BOUND ORGANELLES
Prokaryotic Cells


Notice how everything is floating around together
– not bound separately from one another!
Example:

The DNA is not bound separately from the ribosomes
Eukaryotic Cells

Protists, fungi, plants, and animals consist of
eukaryotic cells.

Eukaryotic cells are much more complex in
structure

They do have a true nucleus and membrane
bound organelles

The DNA in a eukaryotic cell is concentrated
in an area called the nucleus
Eukaryotic Cells
 Notice
how everything is bound in a
membrane separate from one another.
Example:

The DNA is seen inside the nucleus which
has a nuclear membrane separate it from
everything else!
Compare, Compare!
 Prokaryotic
Cell
 Eukaryotic
Cell
o What are some similarities?
o What are some differences?