Protein or the physical region of the protein that participates in chemical catalysis. In solution proteins also undergo variation in structure through thermal vibration and the collision with other molecules. Proteins can be informally divided into three main classes, which correlate with typical tertiary structures: globular proteins, fibrous proteins, and membrane proteins. Almost all globular proteins are soluble and many are enzymes. Fibrous proteins are often structural, such as collagen, the major component of connective tissue, or keratin, the protein component of hair and nails. Membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass
The dogs and the lion's skin The dogs and the lion's skin The dogs and the lion's skin is a fable ascribed to Aesop and is numbered 406 in the Perry Index. However, it is only found in a mediaeval Greek manuscript claiming to be a translation from the Syriac (Syntipas, Fable 19). The story relates how some dogs, finding the skin of a lion, began to tear it to pieces. Seeing them, a passing fox remarked, "If this lion were alive, you would soon find out that his claws were stronger than your teeth." The moral in the original commented that "the fable is for