Macromolecules: Proteins Proteins are the most common organic molecule in living cells. They are made of carbon, hydrogen, oxygen, nitrogen and sometimes sulfer. CHON(S) Proteins are made of amino acids. There are approximately 20+ amino acids. Of the more than 20 amino acids our bodies require, eight (nine in some older adults and young children) cannot be made by the body in sufficient quantities to maintain health. These amino acids are considered essential and must be obtained from food.

Proteins: Structure Amino acids have three parts: The 20+ amino acids differ only in their R-group

Generalized Formula for Amino Acid H Acid group R C COOH NH2 Rest of the molecule Amino group

Amino Acid Groups H NH2 =N H O Double Bond COOH =C O H

Proteins: Structure Compare amino acids: Valine Leucine Glutamic Acid

Amino Acids Essential Amino Acids Hydrophilic Hydrophobic

Proteins Proteins are large complex polypeptides. Think of the amino acids as letters and proteins as words in making up a sentence. Proteins may contain as few as 50 or as many as 3,000 amino acid molecules. The number of possible combinations of amino acids is staggering. We have tens of thousands of different proteins.

Proteins Amino acids are joined by means of dehydration synthesis. An OH from the acid group of one amino acid joins to an H from the amino group of the other amino acid. A water molecule is formed, and a C-N bond is formed between the two amino acids. The C-N bond is called a peptide bond. Dipeptide: 2 amino acids joined Polypeptide: 3 or more amino acids joined. Needed for muscles, skin, cell membranes, and enzymes

Dehydration Synthesis

Proteins: Structure The protein formed depends on: which amino acids were chosen, their order (sequence), and how many of each How are they formed? The DNA

Secondary Arrangement of atoms Primary Amino acid sequence Protein Structure Tertiary 3D Structure Quarternary Spatial Interaction

Biology/Chemistry of Protein Structure Primary Secondary Tertiary Quaternary Assembly Folding Packing Interaction S T R U C T U R E P R O C E S S

Protein Folding Proteins shape is determined by the sequence of the amino acids The final shape is called the conformation and has the lowest free energy possible Denaturation is the process of unfolding the protein Can be down with heat, pH or chemical compounds In the chemical compound, can remove and have the protein renature or refold

Types of Proteins Globular Proteins – most of the proteins are Compact shape like a ball with irregular surfaces Enzymes are globular Fibrous Proteins – usually span a long distance in the cell 3-D structure is usually long and rod shaped

Nutrition: Proteins Dietary proteins are powerful compounds that build and repair body tissues, from hair and fingernails to muscles. In addition to maintaining the body’s structure, proteins speed up chemical reactions in the body, serve as chemical messengers, fight infection, and transport oxygen from the lungs to the body’s tissues.

Nutrition: Proteins Although protein provides 4 calories of energy per gram, the body uses protein for energy only if carbohydrate and fat intake is insufficient. When tapped as an energy source, protein is diverted from the many critical functions it performs for our bodies.

Nutrition: Proteins Animal proteins, found in such food as eggs, milk, meat, fish, and poultry, are considered complete proteins because they contain all of the essential amino acids our bodies need. Plant proteins, found in vegetables, grains, and beans, lack one or more of the essential amino acids. However, plant proteins can be combined in the diet to provide all of the essential amino acids.

Nutrition: Proteins A good example is rice and beans. Each of these foods lacks one or more essential amino acids, but the amino acids missing in rice are found in the beans, and vice versa. So when eaten together, these foods provide a complete source of protein. Thus, people who eat only vegetables (see Vegetarianism) can meet their protein needs with diets rich in grains, dried peas and beans, rice, nuts, and tofu, a soybean product.

Nutrition: Proteins Experts recommend that protein intake make up only 10 percent of our daily calorie intake. Some people, especially in the United States and other developed countries, consume more protein than the body needs. Extra amino acids cannot be stored for later use, the body destroys these amino acids and excretes their by-products.

Nutrition: Proteins Alternatively, deficiencies in protein consumption, seen in the diets of people in some developing nations, may result in health problems. Marasmus and kwashiorkor, both life-threatening conditions, are the two most common forms of protein malnutrition.

Enzymes Enzyme, any one of many specialized organic substances, composed of polymers of amino acids, that act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms. The name enzyme was suggested in 1867 by the German physiologist Wilhelm Kühne (1837-1900); it is derived from the Greek phrase en zymç, meaning "in leaven.” Those enzymes identified now number more than 700.

Enzymes Enzymes are classified into several broad categories, such as hydrolytic, oxidizing, and reducing, depending on the type of reaction they control. Hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds through reaction with water molecules. Oxidizing enzymes, known as oxidases, accelerate oxidation reactions; reducing enzymes speed up reduction reactions, in which oxygen is removed. Many other enzymes catalyze other types of reactions.

Enzymes Individual enzymes are named by adding ‘ase’ to the name of the substrate with which they react. The enzyme that controls urea decomposition is called urease; those that control protein hydrolyses are known as proteinases. Some enzymes, such as the proteinases trypsin and pepsin, retain the names used before this nomenclature was adopted.

Enzymes Some enzymes, such as pepsin and trypsin, which bring about the digestion of meat, control many different reactions, whereas others, such as urease, are extremely specific and may accelerate only one reaction. Still others release energy to make the heart beat and the lungs expand and contract. Many facilitate the conversion of sugar and foods into the various substances the body requires for tissue-building, the replacement of blood cells, and the release of chemical energy to move muscles.

Enzymes As a class, enzymes are extraordinarily efficient. Minute quantities of an enzyme can accomplish at low temperatures what would require violent reagents and high temperatures by ordinary chemical means. About 30 g (about 1 oz) of pure crystalline pepsin, for example, would be capable of digesting nearly 2 metric tons of egg white in a few hours.

Enzymes The kinetics of enzyme reactions differ somewhat from those of simple inorganic reactions. Each enzyme is selectively specific for the substance in which it causes a reaction and is most effective at a temperature peculiar to it. Although an increase in temperature may accelerate a reaction, enzymes are unstable when heated.

Enzymes Enzymes are proteins that act as a catalyst. (Catalysts are substances that increase the rate of a chemical reaction.) Enzymes are not used up or changed by a reaction. Enzymes are specific in their actions. Enzymes work best under specific conditions.

Enzymes Substrate: The substance that the enzyme causes to react.

Industrial Application of Enzymes Industry Application Enzymes Fruit juice/Wine Juice extraction Clarification Starch hydrolys Pectinase Cellulase Hemicellulase Starch hydrolysis Baking Dough conditioner Bread volume Crumb structure Crust colour Antistaling α-amylase Amyloglucosidase protease Others Fat modification Oxygen removal Confectionery Softening Lipase Glucose oxidase Invertase

Industry Application Enzymes Starch Glucose syrup α-amylase β-amylase Amyloglucosidase Pullulanase Glucosisomerase Dairy Cheese Cheese flavour Lactose hydrolys Rennin Lipase Protease Lactase