Carbohydrate Chemistry (1) Biochemistry 1 PDF

carbohydrate chemistry (1) Biochemistry 1 Code (4125) Objectives By the end of the lecture, the student should know: ❑ Definition of carbohydrates. ❑ Importance of carbohydrates. ❑ Classification of carbohydrates. ❑ Monosaccharides. ❑ Derivatives of monosaccharides. ...

carbohydrate chemistry (1) Biochemistry 1 Code (4125) Objectives By the end of the lecture, the student should know: ❑ Definition of carbohydrates. ❑ Importance of carbohydrates. ❑ Classification of carbohydrates. ❑ Monosaccharides. ❑ Derivatives of monosaccharides.  DEFINITION of carbohydrates Carbohydrates are biomolecules consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. As hydrogen and oxygen in carbohydrates were found to be present in the same proportion as in water H2O (2:1) (Glucose, C6 H12O6), So carbohydrates “Carbon Hydrate” derive their name from a misleading concept “Hydrates of Carbon”. This term is not a perfect derivation as many carbohydrates do not have the same proportion as water. (Deoxyribose, C5H10 O4) CHEMICAL DEFINITION Polyhydroxy aldehydes or ketones or substances that yield these compounds on hydrolysis. Polyhydroxy: containing more than one hydroxyl group (-OH). The functional group of carbohydrates, is the carbonyl group which may be either, Aldehyde Group (H-C=O) or Ketone Group (C=O)  CARBONYL GROUPS H-C=O CH2OH   H-C-OH C=O   OH-C-H OH-C-H GLUCOSE   H-C-OH FRUCTOSE--> H-C-OH   H-C-OH H-C-OH   CH2OH CH2OH  Importance of CARBOHYDRATES The most abundant organic molecules in nature. Important source of energy for cells. Provide energy storage; plants store energy in a complex carbohydrate form called starch. Humans and other vertebrates store energy in a complex carbohydrate form called glycogen. Form structural components of many organisms: cellulose of plants; exoskeleton of insects, cell wall of microorganisms. Form a part of RNA, DNA, and several coenzymes (NAD,FAD )  Classification Carbohydrates are classified according to the number of saccharide (Greek Sakcharon meaning "Sugar") units as: Monosaccharides: contain one saccharide unit. Disaccharides: contain 2 monosaccharide units per molecule. Oligosaccharides: contain 3 to 10 monosaccharide units per molecule. Polysaccharides: contain more than 10 monosaccharide units per molecule.  Monosaccharides Monosaccharides are classified 1. According to the number of carbon atoms: Trioses: contain 3 carbon atoms as Glyceraldehyde, Dihydroxyacetone Tetroses: contain 4 carbon atoms as Erythrose, Erythrulose Pentoses: contain 5 carbon atoms as Ribose, Ribulose Hexoses: contain 6 carbon atoms as Glucose, Fructose The suffix ose denotes sugar, and the prefix indicates the number of carbon. 2. According to the presence of aldehyde or ketone groups into : Aldoses Ketoses EXAMPLES OF MONOSACCHARIDES NO. OF CARBON ALDOSES KETOSES ATOMS 3C, TRIOSE Glyceraldehyde Dihydroxyacetone 4C, TETROSE Erythrose Erythrulose 5C, PENTOSE Ribose Ribulose 6C, HEXOSE Glucose, Galactose, Fructose Mannose Trioses Tetroses (Aldotetrose) (Ketotetrose) Pentoses H-C=O CH2OH   H-C-OH C=O  Ribose  H-C-OH Ribulose --> H-C-OH   H-C-OH H-C-OH   CH2OH CH2OH (Aldopentose) (Ketopentose) Hexoses (Aldohexose) (ketohexose)  Galactose Mannose (Aldohexose) (Aldohexose)  Important derivatives of Monosaccharides 1- Sugar alcohols 2- Sugar Acids 3- Deoxy-sugars 4- Amino-sugars 1- Sugar alcohols (Reduction Products) Monosaccharides, may be reduced at carbonyl carbon to the corresponding alcohols. Glucose is reduced to sorbitol (Sweetener, Laxative) Mannose is reduced to mannitol (Sweetener) Galactose is reduced to dulcitol (Culture media) 2- Sugar Acids (Oxidation Products) These are produced by oxidation of aldehyde group, primary alcohol group or both. a- Aldonic acids: Oxidation of aldehyde group (H-C=O) to carboxyl group (COOH).Glucose is oxidized into gluconic acid. b- Uronic acids: Oxidation of primary alcohol group (CH2OH) into carboxyl group (COOH). Glucose is oxidized into glucuronic acid. c- Aldaric acids: oxidation of both aldehyde group and primary alcohol group into carboxyl group Glucose is oxidized to glucaric acid (Di-carboxylic acids). 3- Deoxy-sugars They are sugars in which hydroxyl group is replaced by hydrogen atom leading to the net loss of an oxygen atom. Ribose is converted to deoxyribose, hydroxyl group of C2 of ribose is removed and replaced by hydrogen. It is present in the structure of DNA. 4- Amino-sugars In these sugars, the hydroxyl group at C2 is replaced by an amino group (NH2) Glucosamine: occurring in heparin and hyaluronic acids. Galactosamine: occurring in chondroitin sulphate. Optical activity of Monosaccharides The asymmetric carbon atom : is a carbon atom attached to four different atoms or groups as middle carbon of glyceraldehyde.  Plane polarized light (PPL) is a light vibrates in only one plane. It is produced by the passage of ordinary light through a prism of pure calcium carbonate (polarizing filter).  Optical activity is the ability of the asymmetric carbon atoms to rotate the plane polarized light. When a beam of polarized light is passed through sugars, they will be rotated either towards right or left. Dextrorotatory ( + ) substance rotates PPL to Right Levorotatory ( - ) substance rotates PPL to Left Optical activity is measured by polarimeter. Monosaccharides of biological importance (I)Pentoses Riboses Enters in the structure of nucleic acids (RNA,DNA) Enters in the structure of coenzymes as NAD and FAD II) Hexoses - Glucose It is the main sugar in blood It is the major source of energy in mammals - Galactose It can be converted into glucose in liver It is synthesized in lactating mammary glands to form milk sugar (lactose) - Fructose It can be converted into glucose in liver. It is present in seminal fluid Thank you