Structures of Amino Acid, Protein, Glucose, Carbohydrates and Fatty Acids - Article Example

CHEMISTRY Structure of amino acid: Basic structure of an amino acid contains an amine group, a carboxyl group and a variable side chain attached to central carbon chain. The carbon atom to which the carboxyl group is attached to is called the alpha carbon. The carbon atom in central skeleton next to alpha carbon is beta carbon and so on. Different amino acids differ in their side chains; the simplest being glycine having a Hydrogen in side chain attached to alpha carbon. The side chain can be attached to any of the carbon atoms in the central carbon skeleton, yielding alpha-, beta-, gamma- amino acids. Polar and Non-Polar amino acids: The side chain of the amino acid can render it slightly polar or non-polar. The polar amino acids can be either slightly acidic or basic in nature; i.e. they form acidic solutions or basic solutions when dissolved in water. Structure of Protein The complexity of protein structure is illustrated in the four tiers of conformations a protein takes. Starting from the primary sequence of amino acids to the quaternary globular structure of protein; every level increases in intricacy. Primary structure of a Protein: The primary structure of a protein is the sequence of amino acids in the macromolecule. The amino acids in a protein macromolecule are linked together via an amide bond which comes into existence as a result of a condensation reaction. Condensation reaction: A chemical reaction in which two entities are covalently linked to each other with release of a water molecule. In synthesis of proteins and polypeptides, the reaction takes place between carboxyl group of one amino acid and amine group of another amino acid. The result is carboxyl group carbon atom covalently linked to nitrogen atom of amine group, with release of water molecule. Scores of amino acids are linked together in this way to form the primary structure of proteins. The primary structure is read from the amino terminal i.e. from the amino acid which has a free amine group and it ends with the free carboxyl functional group of last amino acid. Secondary structure of protein: H-bonds: The primary structure of the protein forms local areas of highly stable repetitious conformations such as alpha helices and beta sheets. These secondary structure conformations are stabilized by hydrogen bonds between the electropositive hydrogen of amine group and electronegative oxygen of carboxyl group. Hydrogen bonds, though being non-covalent in nature, play a major role in determining physical properties of protein macromolecules. Glucose: Glucose, with chemical formula C6H12O6, is a 6 carbon sugar, having an aldehyde group at one end. The orientation of hydrogen atoms above and below the plane of the ring gives rise to two different stereoisomers of glucose: alpha glucose and beta glucose. In alpha glucose, the hydrogen attached to C1 carbon is above the plane of the ring and in beta glucose, it is below the plane of the ring. Carbohydrates formed by alpha-glucose molecules Maltose: alpha linkage glucose disaccharide Two glucose molecules linked together via an alpha 14 bond form Maltose sugar. Maltose can be broken down into simple glucose to be introduced into biochemical pathways for release of energy. Starch: Polysaccharide of alpha glucose molecules A large number of alpha glucose subunits are linked together via glycosidic linkages producing complex carbohydrate starch. The glycosidic linage is again alpha 14 linkage. Plants store their food in the form of starch. Starch is also present in staple foods like rice wheat and potatoes, consumed world over. Breakdown of starch gives maltose which can be further broken down to glucose monomers for release of energy. Carbohydrates formed by beta-glucose molecules: Cellobiose: beta linkage The beta glucose isomer forms the dissacharide Cellobiose via 14 glycosidic linkage. The beta linked carbohydrates cannot be broken down by enzymes produced by animals; although bacterial enzymes can cleave cellobiose to give glucose molecules. Cellobiose is structural component of paper and jute. Cellulose: beta linkage A large number of beta glucose subunits are linked together via 14 glycosidic bonds giving rise to the polysaccharide cellulose, the most common organic compound on earth. It is a component of the plant cell wall. Complete breakdown yields glucose molecules while partial breakdown of cellulose can give rise to smaller polysaccharides. Breakdown of cellulose can occur in some animals due to presence of bacterial enzymes in their guts, however humans have limited ability to break down the cellulose. Fatty Acids: Organic compounds that contain a long aliphatic chain and atleast one carboxylic functional group. They are divided according to the number of carboxylic groups present, i.e. monocarboxylic acids, dicarboxylic acids and so on. Also, the aliphatic chain can be saturated or unsaturated, forming another basis for the classification (Zamora, 2005-2008). Saturated fatty acids: These fatty acids have no double bonds in the long aliphatic chain and usually have even number of carbon atoms. High percentage of saturated fatty acids are present in fats that are solids at room temperature. Unsaturated fatty acids: These fatty acids contain one or more double bonds in the aliphatic chain, decreasing the melting and boiling points of these acids. Oils and fats that are liquid at room temperature have a larger proportion of unsaturated fatty acids in them. The unsaturated fats contribute towards increasing high-density lipoproteins (HDL) in the blood. HDL is also known as good cholesterol and level of HDL should be high in blood. On the other hand, saturated fatty acids increase the low-density lipoprotein (LDL) in the blood which is supposed to be low in level for a healthy body. HDL cholesterol works to scavenge the LDL cholesterol and decreases its level in the blood. It transports LDL to the liver where it is broken down. Therefore saturated fatty acids increase the blood cholesterol level as LDL persists in the blood whereas HDL moves around in the body forming packets of cholesterol (The National Cholesterol Education Program, 2001). References University of Arizona, 2003. The Chemistry of Amino Acids. [image online] available at: Brooklyn College, 2001. The Three Dimensional Structure of Protein. [online] available at: Kellie, 2009. Biomolecules. [image online] available at: Shaw, Michael, 2005. The Molecules of Life: Biochemistry. [image online] available at: Pearson Education, 2008. [image online] available at: Biosynth, 2006. Carbohydrates and Inositols. [image online] available at: Zamora, Antonio, 2005-2008. Fats, Oils, Fatty Acids, Triglycerides. [online] available at: Corkill, Jeff, 2010. Triacylglycerols (TAGs), Soaps and Detergents at the molecular level. [online image] available at: The National Cholesterol Education Program, 2001. Blood Cholesterol (HDL & LDL). [online] available at: Read More