Many scientists contributed to the cell theory.
The cell theory grew out of the work of
many scientists and improvements in the
microscope.
More was learned about cells
as microscopes improved.
The cell theory is a unifying
concept of biology.
The cell theory has three principles.
• All organisms are made of cells.
3.1 Cell Theory
• 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.
• All cells are enclosed by a
membrane.
• All cells are filled with
cytoplasm.
• All cells have DNA
Bacterium
(colored SEM; magnification 8800x)
cell membrane
cytoplasm
There are two cell types: eukaryotic cells and
prokaryotic cells.
• Eukaryotic cells have a
nucleus.
• Eukaryotic cells have
membrane-bound
organelles.
nucleus
cell membrane
organelles
There are two cell types: eukaryotic cells and
prokaryotic cells.
• Prokaryotic cells do not
have a nucleus.
• Prokaryotic cells do not
have membrane-bound
organelles.
nucleus
cell membrane
organelles
cytoplasm
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.
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.