Cell Theory
Cells are composed of three principle areas (regions):
Plasma Membrane, Cytoplasm, Nucleus

Cytoplasm
– material between plasma membrane and the nucleus
Site where most cellular activities happen
Consists of three major elements:
Cytosol
Organelles
Inclusions
---Cytosol – viscous fluid that suspends the organelles and inclusions and gives cell shape. Largely water with dissolved protein, salts, sugars, and other solutes
---Cytoplasmic organelles – metabolic machinery of the cell
---Inclusions – storage areas for nutrients such as glycosomes, glycogen granules, and pigment

Nucleus
-Contains nuclear envelope, nucleoli, chromatin, and distinct compartments rich in specific protein sets
-Gene-containing control center of the cell
-Contains the genetic library with blueprints for
nearly all cellular proteins
-Dictates the kinds and amounts of proteins to be synthesized
-Most cells have a single nucleus, but some are multinucleated and are often associated with large cytoplasmic mass and high protein production
-Mature red blood cells (RBCs) are anuclated and do not divide
-Largest of all cytoplasmic organelles
-Divided into three regions:
Nuclear envelope, Nucleoli, Chromatin

Chapter 3: Cells: The Living Units

21. List the three major regions of a generalized
cell and indicate the function of each.

Plasma Membrane (Cell Membrane)
-Defines the extent of the cell
-Separates intracellular fluids from extracellular fluids
-Encloses all of the cell organelles
-Plays a dynamic role in cellular activity
-Plasma membrane is a selective (or differentially) permeable barrier. E.g. allows some substances to pass and blocks others
-Plasma membrane moves things across by:
-Active processes: require ATP to cross P.M.
-Passive processes: require no energy from cell