Proteins

Proteins are large molecules, much longer than peptides, made up of long polypeptides or several polypeptides attached to each other by chemical bonds, such as disulfide bonds, between the sulfur-containing amino acids. Proteins in the form of enzymes act as catalysts to enable biological reactions: amylase in our saliva breaks down starch, and alcohol dehydrogenase in yeast produces alcohol from glucose. Some proteins provide structural integrity to cells and tissues, such as the actin and myosin proteins that give the muscle tissues in meat their firm texture. Others form the receptors in our bodies that help us sense light, sound, aroma, taste, and pain through extremely complex communication pathways.