Two or more polypeptide chains, each with its own tertiary structure.

A dipeptide can be broken into two amino acids by dehydration synthesis.

The mediastinum encloses the heart and lungs. 

This inventor is often blamed for the rapid spread of cotton production in the American South before the Civil because of his invention of the cotton gin.  What is his name?

Isotopes differ from each other only in the number of electrons the atom contains.

A bond in which electrons are completely lost or gained by the atoms involved.

The pH of body fluids must remain fairly constant for the body to maintain homeostasis.

Identify the level of organization. Protein structure achieved when alpha-helical or beta-pleated regions of the polypeptide chain fold upon one another to produce a compact ball-like, or globular, molecule.

Thymine.

Double bonds have 2 shared electrons.