Objectives Describe the chemical composition and general structure of carbohydrates. Describe three classes of carbohydrates, how they are synthesized, specific examples of each (name, empirical and structural formulas) and their functions. Describe the chemical composition and structures of lipids Describe the formation of a triglyceride Describe the 4 levels of protein structure. Describe the major functions of proteins.

Carbohydrates A carbohydrate is a large biological molecule consisting only of carbon (C), hydrogen (H), and oxygen (O), which are combined as (,, where n is 3 or more. The general empirical formula for a carbohydrate is CH 2 O. If a carbohydrate has 5 carbons atoms, what would be its empirical formula? C 5 H 10 O 5

Functions of Carbohydrates Provide energy source: A fuel source when catabolized during cellular respiration. Energy is stored in the chemical bonds within the molecule and released during cellular respiration. Usually simple sugars. Provide energy storage: Plants store energy in a complex carbohydrate form called starch (amylose). Animals store energy in a complex carbohydrate in their muscle tissue and liver in the called glycogen. Structural Building Material: Plants build their cell walls of a complex carbohydrate material called cellulose. Animals such as arthropods build their exoskeletons of a complex carbohydrate called chitin. Chitin is also found in the cell walls of Fungi.

Classes of Carbohydrates There are three major classes of carbohydrates: 1. Monosaccharides (simple sugars) These are the monomers or building blocks for all other classes of carbohydrates. Examples: glucose, fructose, galactose, and ribose. 2. Disaccharides are produced by joining two simple sugars by dehydration synthesis forming a covalent bond between them. Examples: sucrose (table sugar), maltose, lactose 3. Polysaccharides (complex carbohydrates) are produced by joining many monosaccharides together by many dehydration synthesis reactions forming a polymer molecule. Examples: amylose, glycogen, cellulose, and chitin

Monosaccharides (Simple sugars) They may exist in a linear molecule or in ring forms. They are classified according to the number of carbon atoms in their molecule. 5 carbons are called pentoses ex. Ribose 6 carbons are called hexoses ex. Glucose MONOSACCHARIDES ARE THE BUILDING BLOCKS FOR ALL OTHER CARBOHYDRATES!

Monosaccharide Isomers H H—C—OH C O H H H C OH H OH C C OH H OH H H—C—OH O H C OH OH H C H OH H—C—OH H α- GLUCOSE FRUCTOSE What is the empirical formula for these molecules?C 6 H 12 O 6

Disaccharide Formation and Structure Disaccharides are formed when two monosaccharides are joined by dehydration synthesis reaction.

Disaccharide Formation and Structure CH 2 OH H O H OH OH CH 2 OH H O H HO OH + H20H20 CH 2 OH H O H OH CH 2 OH H O H OH O α- GLUCOSE MALTOSE

Polysaccharide Structure and Formation Polysaccharides are chains of monosaccharides that have been joined by many dehydration synthesis reactions. The function of the polysaccharide depends on what type of isomer of glucose the polysaccharide is made. This determines how the glucose molecules bond together (linkage) and whether they can be used for energy storage or structural molecules.

(a)  and  glucose ring structures (b) Starch: 1–4 linkage of  glucose monomers (c) Cellulose: 1–4 linkage of  glucose monomers  Glucose  Glucose Polysaccharide Structure

13 INTRODUCTION Lipids are heterogeneous group of water insoluble (hydrophobic) organic molecules. They are fats, oils, steroids and waxes. Insoluble in water, but soluble in non-polar solvents such as ether, chloroform.

14 BIOLOGICAL IMPORTANCE OF LIPIDS Important dietary constituents. Have high energy value. Fats stored in adipose tissue, serve as thermal insulator. With proteins and carbohydrates, they form important cellular constituents (lipoproteins, glycolipids).

15 CLASSIFICATION OF LIPIDS Classified into simple, complex and derived lipids 1.SIMPLE LIPIDS: Esters of fatty acids (FA) with various glycerol a. Fats: esters of FA with glycerol b. Waxes: esters of FA with higher molecular weight alcohols 2. COMPLEX LIPIDS: Esters of FA containing groups in addition to an alcohol and a FA a. Phospholipids: Esters of FA with alcohol and phosphoric acid.

16 CLASSIFICATION CONTD….. 3. DERIVED LIPIDS: These include FA, glycerol, steroids, some alcohols, fatty aldehydes and ketone bodies.  Acylglycerols (glycerides), cholesterol & cholesterol esters are termed neutral lipids because, they are uncharged.

Lipid structure (Triglyceride) A triglyceride is composed of an alcohol called glycerol covalently bonded to three fatty acid molecules by dehydration synthesis reactions. This process forms three ester groups between the alcohol and one with each fatty acid chain.

Figure 5.10b (b) Fat molecule (triacylglycerol) Ester linkage

Introduction Proteins are polymers of amino acids linked covalently through peptide bonds. Proteins are large molecules and can be split into smaller units by hydrolysis-amino acids.

Proteins: Classification Depending upon their solubility and physical properties, proteins are divided into three classes. 1- Simple proteins: Simple proteins are those which contain only amino acids. e.g. albumin and globulin 2- Conjugated proteins: Conjugated proteins are those which contain a non amino acid component in addition to the amino acids. e.g. lipoprotein, phosphoproteins etc. 3- Derived proteins: Derived from simple proteins (denaturation) e.g. peptones.

Properties of Proteins Molecular weights range from several hundred thousand Generally proteins are soluble in water, except the membrane proteins which are hydrophobic Absorption maxima in the ultraviolet region Proteins are charged molecules, but the charge depend on the pH of the buffer. Move under an electric field and can be separated by electrophoresis

Functions of Proteins 1.Proteins build new tissues of the body. 2.They maintain and replace damaged tissues. 3.They carry out regulating activities as enzymes and hormones. 4.They are protective as antibodies. 5.They help in other activities such as movement of skeletal muscles, transport of oxygen, pigmentation of skin etc.

Four Levels of Protein Structure The primary structure of a protein is its unique sequence of amino acids Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain Tertiary structure is determined by interactions among various side chains (R groups) Quaternary structure results when a protein consists of multiple polypeptide chains

4 Levels of Protein Structure