Cell Theory
The cell theory grew out of the work of
many scientists and improvements in the
microscope.
Many scientists contributed to the cell theory.
More was learned about cells
as microscopes improved.
The cell theory is a unifying
concept of biology.
3.1 Cell
Theory
The cell theory has three principles.
• All organisms are made of cells.
• All existing cells are
produced by other
living cells.
• The cell is the most
basic unit of life.
Eukaryotic cells have a nucleus
and membrane-bound organelles;
prokaryotic cells do not.
All cells share certain characteristics.
• Cells tend to be microscopic.
cell membrane
• All cells are enclosed by a
membrane.
• All cells are filled with
cytoplasm.
• All cells have DNA
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
There are two cell types: eukaryotic cells and
prokaryotic cells.
• Eukaryotic cells have a
nucleus.
nucleus
• Eukaryotic cells have
membrane-bound
organelles.
organelles
cell membrane
There are two cell types: eukaryotic cells and
prokaryotic cells.
• Prokaryotic cells do not
have a nucleus.
nucleus
• Prokaryotic cells do not
have membrane-bound
organelles.
organelles
cell membrane
cytoplasm
CELL STRUCTURE AND FUNCTION
CHART
PLANT CELL
ANIMAL CELL
1. Cell Wall
• (Plants only) inflexible barrier “protecting” the
cell and giving it support. Is not selectively
permeable. It is a rigid structure.
2. Cell Membrane
• Boundary (“wall”) between the cell and the
environment. Allows nutrients/ regulates
movement in and out of the cell. (“Selectively
Permeable”).
3. Microtubules
• Part of cell skeleton that act as a scaffold to
maintain the shape of a cell. (“Supporting
Framework”)
4. Nucleus
• Central leader of the cell. Surrounded by
nuclear envelope. Contains directions to make
proteins and genetic information, DNA or
RNA. (“Control Center of Cell”); inside is the
nucleolus which makes ribosomes.
5. Nuclear Membrane
• The outer lining or wall of the nucleus.
(Sometimes this is called the nuclear
envelope.)
6. Chromatin
• Master set of directions for making proteins.
Contents are in the form of Genes & DNA.
7. Vacuole
• Membrane-bound “compartment” used for
temporary material “storage”. (In plants it is
found in the center of cell, in animals it is off
to the side)
8. Mitochondria
• Membrane-bound organelle that transforms
(“generates”) energy from the cell.
(“Powerhouse of cell”)
9. Lysosome
• Contain enzymes which digest excess
organelles, food particles, viruses, and
bacteria. The “vacuum cleaner” of a cell. They
break down organelles not needed.
10. Rough Endoplasmic
Reticulum
• The site of cellular chemical reactions. Rough
ER means ribosomes are attached and are
synthesizing/making proteins.
(“Transportation system with workers”)
11. Smooth Endoplasmic
Reticulum
• The site of a cellular chemical reaction.
Smooth ER has no ribosomes present.
(“Transportation system with no workers”)
12. Ribosomes
• Site where the cell produces proteins
according to the DNA instructions, which
comes from the nucleus. (“Workers of cell”)
– Bound Ribosomes: make proteins for use outside
cell
– Free Ribosomes: make proteins for use inside cell
13. Golgi Apparatus
• Flattens and packages proteins to be sent to
their appropriate destination (The
“UPS/FedEx” of the cell)
14. Chloroplast
• (Found in green plants and some protists only)
– converts light energy (SUN) to chemical
energy (SUGAR).
• - Contains Chlorophyll
15. Cytoplasm
• Clear, gelatinous fluid inside a cell which
suspends and holds a cell’s organelles, such as
the nucleus.
16. Centrioles
• (Animal Cells Only) Play a role in cell division
Cytoskeleton
Network of fine tubes
and threads. Provides
internal structural
support.
Cilia, Pilli, and Flagella
Structures used to enable
movement of cells or sometimes to
propel substances across outer
surface of the cell. Predominantly
protein in composition.
Quiz of the cell
• Know all organelles found in a prokaryotic cell
• Know all organelles found in a eukaryotic cell