Carbohydrates PDF - Medical Chemistry

Almaaqal University Medical Chemistry Collage of Dentistry Carbohydrates and oral health Dr/ Wael Sobhy Darwish 1ST stage&2024  INTRODUCTION Biochemistry can be defined...

Almaaqal University Medical Chemistry Collage of Dentistry Carbohydrates and oral health Dr/ Wael Sobhy Darwish 1ST stage&2024  INTRODUCTION Biochemistry can be defined as the science concerned with the study of chemical reactions that occur in living organisms. The cell is the structural unit of living systems. Thus, biochemistry can also be described as the science concerned with the structures, functions and interactions of biological molecules, such as proteins, nucleic acids, carbohydrates and lipids, which provide the structure of cells and perform many of the functions associated with life. The Big Four "THE BIG 4" MACROMOLECULES  Before you can understand the topics in this unit there are some key vocabulary terms you need to know. Macromolecule Polymer Monomer  So what is a macromolecules? Area very large molecule consisting of many smaller structural units linked togethe by a process called dehydration synthesis such as a polymer or protein All biological macro-molecule are made up of a small number of elements: Carbon, Hydrogen, Oxygen, (Nitrogen, Phosphorus)  Three of the four classes of macromolecules—carbohydrates, proteins, and nucleic acids—form chain-like molecules called polymers. A polymer gnidliub ralimis ynam fo gnitsisnoc elucelom gnol a si blocks called monomers linked by covalent bonds. A monomer is a molecule that can undergo polymerization, creating macromolecules. Large numbers of monomers combine to form polymers in a process called polymerization.  The Synthesis and Breakdown of Polymers Monomers form larger molecules by condensation reactions called dehydration reactions HO 1 2 3 H HO H Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new bond H2O HO 1 2 3 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer Polymers can disassemble by Hydrolysis HO 1 2 3 4 H Hydrolysis adds a water H2O molecule, breaking a bond HO 1 2 3 H HO H Hydrolysis of a polymer  Carbohydrates Carbohydrate are biomolecules consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with the general formula Cn(H2O)n = CnH2nOn There are some carbohydrates, which do not have this general formula There are substances which are not carbohydrates but have the formula CnH2nOn Importance of carbohydrates: 1)The chief source of energy. 2)Important structural components in animal and plant cells. 3)Important part of nucleic acids, free nucleotides and coenzymes. 4)Major antigens are carbohydrates in nature, e.g., blood group substances. 5)Biological role as part of hormones and their receptors and enzymes.  Classification of Carbohydrates Cannot be hydrolyzed Hydrolyzed to Hydrolyzed to monosaccharides or into smaller unit smaller units oligosaccharide  Classification of carbohydrates A-According to the hydrolysis products (no. of individual simple units): 1-Monosaccharides: contain 1 sugar unit (can not be hydrolyzed). Ex: Glucose, galactose , mannose, & fructose. 2- Disaccharides: contain 2 sugar units. Ex: Maltose, lactose & sucrose. 3- Oligosaccharides: contain 3-10 sugar units. 4- Polysaccharides: more than 10 sugar units. Ex: Starch, glycogen & cellulose.  Monosaccharides Simplest carbohydrates, composed of single sugar unit according to the formula CnH2nOn Monosaccharides can be classified according to :- (1)The number of carbon atoms present in the monosaccharide The name of any monosaccharides composed of two parts [prefix + suffix] Prefix = No. of C. atoms Suffix = ose A monosaccharide containing three carbon atoms is called a triose A monosaccharide containing four carbon atoms is called a tetrose (pentose? hexose?) (2)Whether they contain an aldehyde or keto group :- (i)Aldoses :- contain C=O in C1 [ aldehyde group] (ii)Ketoses :- contain C=O in C2 [ ketone group]  Stereochemistry of carbohydrates Stereoisomers: - They are compounds having the same structural formula but differ in: i)Arrangement of atoms in the molecule in space ii)Properties. - isany carbon atom attached to 4 different groups. Chiral carbon - Also called Asymmetric carbon. Example :- Glucose Optical activity is the ability of a chiral molecule to rotate the plane of plane-polarized light (The rotation may be clockwise orAnti-clockwise). D- and L- sugars If the rotation was clockwise, the sugar called dextrorotatory, If the rotation was Anti-clockwise, the sugar called levorotatory D-sugar :- The OH of pre-last carbon is on the right L-sugar :- The OH of pre-last carbon is on the left  Monosaccharide of biological importance Glucose a) Major source of energy for humans and animals tissues. (Some cells and tissues e.g. brain and erythrocytes depend mainly on glucose because they cannot oxidize alternative fuels.) b) The body maintains a fairly constant blood glucose level of 70–140 mg/dl at all times. c) Most ingested carbohydrates are absorbed in the form of glucose. d) Glucose can be converted into other sugars in the liver and other tissues [e.g. galactose, fructose, ribose and glycogen.] Galactose a) It is synthesized in mammary gland to form the disaccharide lactose (sugar of milk) b) Presents in tissues as a constituent of galactolipid and glycoproteins.  Fructose a) It is present in semen and is a constituent of disaccharide sucrose b) Seminal fluid is rich in fructose that is formed from glucose and sperms utilize fructose for energy. Ribose a)Ribose and deoxy-ribose form part of the structural backbone of nucleic acids RNA and DNA respectively. b)Ribose enters in the structure of high-energy phosphate compounds (e.g. ATP) and also in the structure of coenzymes such as (e.g. NAD).  Common Disaccharides There are several forms of disaccharides but the most common ones are sucrose, lactose, and maltose. These three are made up of two monosaccharides joined by a covalent bond. Glucose & Fructose Glucose&Galactose 2 Glucose  Starch Is a polymer consisting entirely of glucose monomers Is the major storage form of glucose in plants Glycogen Consists of glucose monomers Is the major storage form of glucose in animals Cellulose Is a polymer of glucose Has different glycosidic linkages than starch Cellulose is difficult to digest Cows have microbes in their stomachs to facilitate this process  Sugars and dental caries Sugars, after being hydrolyzed by salivary amylase, provide substrate for the actions of oral bacteria. They produce excess amounts of acid, which starts attacking your tooth enamel, eventually leading to cavities and tooth decay. The resultant action is the beginning of tooth demineralization causing caries. It’s important to note that these bacteria can use any type of sugar. That includes “natural sugars” like honey and fruits.  Can Sugar Also Cause Gum Disease? Gum disease, or periodontitis, has the same main cause as tooth decay the formation of plaques that eventually move down into your soft gum tissue. Once the bacteria reach the base around your teeth, they can quickly grow and multiply, eventually causing pockets in your gums. Periodontitis can lead to painful, bleeding gums, tooth loss, and bone disease in your jawbone. As with tooth decay, the more sugar you eat, the more bacteria will grow.