Cell Theory

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

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