Concepts of Human Anatomy & Physiology   5/e   Van De Graaff/Fox
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I. Cell Membrane and Associated Structures

Concept: The cell is the basic unit of structure and function in the body. Many of the functions of cells are performed by particular subcellular structures known as organelles. The cell membrane allows selective communication between the intracellular and extracellular compartments and aids cellular movement.

II. Cytoplasm and Its Organelles

Concept: Many of the functions of a cell that are performed in the cytoplasmic compartment result from the activity of specific structures called organelles. Among these are the lysosomes, which contain digestive enzymes, and the mitochondria, where most of the cellular energy is produced. Other organelles participate in the synthesis and secretion of cellular products.

III. Cell Nucleus and Nucleic Acids

Concept: The genetic code is based on the structure of DNA and expressed through the structure and function of RNA. DNA and RNA are composed of subunits called nucleotides, and together these molecules are known as nucleic acids. The sequences of DNA nucleotides direct the synthesis of RNA molecules, and it is through the RNA-directed synthesis of proteins that the genetic code is expressed.

IV. Protein Synthesis and Secretion

Concept: In order for a gene to be expressed, it first must be used as a guide, or template, in the production of a complementary strand of messenger RNA. The mRNA is then itself used as a guide to produce a particular type of protein whose sequence of amino acids is determined by the sequence of base triplets (codons) in the mRNA.

V. DNA Synthesis and Cell Division

Concept: When a cell is going to divide, each strand of the DNA within its nucleus acts as a template for the formation of a new complementary strand. Organs grow and repair themselves through a type of cell division known as mitosis. The two daughter cells produced by mitosis contain the same genetic information as the parent cell. Gametes contain only half the number of chromosomes as their parent cell and are formed by a type of cell division called meiosis.

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