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.

cytoplasm • All cells have DNA 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 nucleus have a 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