3C_Proteins

Proteins Properties Basic Unit of Proteins
 * 1) Sensitive to pH and heat
 * 2) Shape determines its function
 * 3) Special group of proteins are enzymes
 * Amino acids
 * 20 essential amino acids for protein formation
 * contain elements C, H, O, N and sometimes S & P



Proteins are polymers made up of monomers called amino acids. There are 20 different amino acids, amino acids can join in any order to produce an infinite number of different proteins. The only thing that changes between different amino acids is the R group The R group can contain hydrogen and/or carbon and sometimes oxygen, sulphur and nitrogen. Peptide Bond Peptide bond: formed between 2 amino acids in a condensation reaction Two amino acids joined together forms a dipeptide. Protein Structures A condensation reaction joins two amino acids together forming a dipeptide. The bond formed between them is called a peptide bond A chain of many amino acids linked by peptide bonds is called a polypeptide. A protein can consist of one or more polypeptides. Proteins can get broken down by hydrolysis reactions into polypeptides, dipeptides and amino acids. Proteins sub groups Proteins fit into two subgroups, globular proteins and fibrous proteins. Globular proteins, for example enzymes, form roughly a spherical shape and most of them are soluble in water.
 * 1) Primary: order in which amino acids are linked to form a polypeptide chain
 * 2) Secondary: the way the polypeptide chain is coiled and folded, alpha-helix and beta-pleated
 * 3) Tertiary: large globular proteins formed by the coiling and folding the already coiled and folded chain eg enzymes
 * 4) Quaternary: proteins made from 2 more polypeptides eg haemoglobin

The function of a globular protein is determined by its shape, so its shape is vital. The usual function for this subgroup is a chemical function. Fibrous proteins do not form a spherical structure they form long chains and they are insoluble. Fibrous proteins have structural roles, like giving strength or elasticity to certain tissues. Proteins can become denatured causing their shape to change therefore affecting their function. A protein can vibrate due to an increase in temperature, which can cause it to become denatured, causing the weak bonds holding the tertiary or quaternary structure together to break. Functions of Proteins General uses of proteins
 * 1) Synthesis of protoplasm, for growth and repair of worn out cells
 * 2) Synthesis of enzymes and hormones
 * 3) Formation of antibodies to combat diseases
 * 4) Source of energy

Enzymes - are proteins that facilitate biochemical reactions. They are often referred to as catalysts because they speed up chemical reactions. Examples include the enzymes lactase and pepsin. Lactase breaks down the sugar lactose found in milk. Pepsin is a digestive enzyme that works in the stomach to break down proteins in food.

Contractile Proteins - are responsible for movement. Examples include actin and myosin. These proteins are involved in muscle contraction and movement.

Antibodies - are specialized proteins involved in defending the body from antigens (foreign invaders). One way antibodies destroy antigens is by immobilizing them so that they can be destroyed by white blood cells.

Hormonal Proteins - are messenger proteins which help to coordinate certain bodily activities. Examples include insulin, oxytocin, and somatotropin. Insulin regulates glucose metabolism by controlling the blood-sugar concentration. Oxytocin stimulates contractions in females during childbirth. Somatotropin is a growth hormone that stimulates protein production in muscle cells.

Structural Proteins - are fibrous and stringy and provide support. Examples include keratin, collagen, and elastin. Keratins strengthen protective coverings such as hair, quills, feathers, horns, and beaks. Collagens and elastin provide support for connective tissues such as tendons and ligaments.

Storage Proteins - store amino acids. Examples include ovalbumin and casein. Ovalbumin is found in egg whites and casein is a milk-based protein.

Transport Proteins - are carrier proteins which move molecules from one place to another around the body. Examples include hemoglobin and cytochromes. Hemoglobin transports oxygen through the blood. Cytochromes operate in the electron transport chain as electron carrier proteins.

Besides these functions, protein is the basic unit for hair nail and connective tissues. The triple helix of the collagen (a protein) gives our skin the elasticity. That is why it is injected under the sky in cosmetic surgery. - Food Test Buirets Test Solution turns from blue to lilac
 * Red Blood Cells and Haemoglobin
 * A small change in the haemoglobin protien, changes the shape of the whole cell. Sickle cell anaemia