The kidneys are part of which organ system? (You may need to select more than one answer)

A fully-assembled protein composed of 2 or more polypeptides constitutes:

_____ glands have ducts.

Amino acids differ only in their:  

__________ fibers have the highest tensile strength. 

Attraction between two polar molecules constitutes:

Which level of organization is the smallest (or lowest)?

The outer layer of the nuclear envelope is continuous with the rough ER.

Which of the following nucleotide bases is found only in DNA:

____________ are non-membranous organelles that carry out protein translation.