Proteins   One of the most important organic molecules   Almost 50% dry weight of cells   Composed of monomers known as amino acids   Contains hydrogen, carbon, oxygen and nitrogen and a variable side chain (R) R H 3 N – C – COO - H +

 Amino acids link together to form a polypeptide

 Linear arrangement of different amino acids is known as its primary structure

 Amino acids link together to form a polypeptide  Linear arrangement of different amino acids is known as its primary structure  Because of chemical bonding and repulsion, the linear arrangement of amino acids begins to fold taking on one of two distinct shape: Alpha helix Beta pleated sheet Less common Random coil

 When the polypeptide folds into a three- dimensional shape, it is called a protein  The three-dimensional shape of a protein is called its tertiary structure Myoglobin  Binds oxygen  Found in the muscles  Acts as a storage site for oxygen  Makes up the dark meat in chicken

 If two or more polypeptide chains link to form a protein its called it quaternary structure Hemoglobin  Binds oxygen in the lungs and transports it through out the body  Helps to regulate blood pressure

 Shape of the protein is important for its function Ex. Insulin = 51 amino acids

 Shape of the protein is important for its function Ex. Insulin = 51 amino acids

Types of Proteins TypeFunction CommunicationCell signaling Ex. Hormones in the bloodstream DefenseProtection from infection Ex. Antibodies in the bloodstream StructureMechanical support Ex. Collagen in skin & keratin in hair/nails StorageStores nutrients Ex. Albumin in egg whites ContractileMovement Ex. Actin and myosin in muscles TransportCarries other molecules Ex. Hemoglobin HormonesChemical messengers Ex. Growth hormone stimulates bone growth EnzymesSpeed up chemical reactions Ex. Catalase

Just for fun facts: Your hair is composed of all  -helix Spider webs are all  -pleated sheets