Beta pleated sheet is an example of the secondary structure of a protein. The beta sheet is composed of beta strands which are polypeptides linked by hydrogen bonding . Beta strands have a 2 residues repeat and when the polypeptide is fully extended, the distance between adjacent amino acids is 3.5 A. The secondary structure of silk is the beta pleated sheet. The primary structure of silk contains the amino acids of glycine, alanine, serine, in specific repeating pattern. These three amino acids make up 90% of the protein in silk. Concept 5.4: Proteins have many structures, resulting in a wide range of functions. Proteins account for more than 50% of the dry mass of most cells. Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances [Animations are listed on slides that follow the figure] Protein Modeling C: Students will use computer visualization and online resources to construct physical models of the CRISPR Cas9 protein that is being engineered to edit plant and animal cell genomes, and answer a series of questions about the chemistry of protein folding and the interaction of structure and function for model proteins. Chemistry 130 Proteins Part I: Isolation of Casein from Milk. Casein is a milk protein that contains all of the common amino acids and is particularly rich in the essential ones. Cheesemaking is based on the precipitation of casein from milk to form solid curds. The liquid (whey) is then separated from Oct 02, 2008 · Beta pleated sheet This secondary structure has been defined as the secondary level of protein organization in which the backbone of the peptide chain (Beta-strands) is extended into a zigzag arrangement resembling a series of pleats, with the peptide bonds organized in planes of alternating slopes (alternating ascending and descending direction).