Nutrition Chemistry

- Nutrition chemistry is called boichemistry, because it connects chemistry science with biology one. - Saccharides or mono charbohydrates have the general formula . The ratio between hydrogen and oxygen is semilar to that in water ( 2 : 1). - Saccharides are called carbohydrate i.e carbon hydrate, because its general formula is [C_n(H₂O)_n] - Monosaccharides are named simple saccharides as they do not undergo hydrolysis into simpler units i.e they are in the simplest form. - Mono saccarides are polyhydroxy compounds, because they contain many hydroxyle groups in the sugar molecule. They dissolve easily in water because they form hydrogen bonds with water molecules. - Glucose is from aldoses due to the prsence of aldhyde group in the sugar molecule. - Fructose is from ketoses due to the presence of ketone group in the sugar molecule. - Monosaccharides are reduced to polyhydric alcohols by sodium amalgam (Glucose is reduced to sorbitol) as the aldhyde group in the sugar molecule is reduced to primary alcohol group. - Glucose is oxidized by mild oxidizing agent e.g (Br₂/H₂O) to gluconic acid (monobasicity) and oxidized to saccharic acid (di-basicity) by strong oxidizing agent eg. Dil HNO₃. - Disaccharides (sucrose, maltose and lactose) are oligosaccarides, because each molecule is formed from condensation of two monomsaccharides units. - Disaccharides decompose by hydrolysis to two units of monosaccharides which have no fermentation characteristics. - Maltose & lactose have areducing property. They reduce the solutions of Fehling or Benedict to red brick ppt, and reduce the ammonical silver nitrate to silver mirror. - Sucrose has no reducing power, since the aldhydic and ketonic groups in glucose and fructose are linked with each other, so their characteristics disappear. - Osazone compounds are used to differentiate between the different types of sugar. - The poly saccharide molecule is formed from the condensation of more than ten units of mono-saccharides (starch, cellulose or glycogene). - Polysaccharides are natural polymers, as they form from the condenstation of unlimited numbers of units of glucose sugar. - Polysaccarides neither have reducing property nor fermentation characteristic. The general formula is (C₆H₁₀O₅)_n - Starch dissolve in hot water. Its particles swell and explode. - starch does not melt by heating, its colour becomes blue when adding drops of iodine. - Cellulose is insoluble in water, acids or alkalies, but it dissolves in ammoniacal copper II hydroxide [Cu(NH₄)₂](OH) ₂ and precipitate in a glossy form by adding dil. HCl (because the acid is neutralized with ammonical copper II hydroxidel. - Cellulose reacts with acetic acid and cellulose acetate is produced (starting material of synthetic silk) Mercerization: Spun cotton fibers are treated with caustic soda solution, the cotton threads become more tolerant, brightes and easily to be dye. - Herbivorous intestine can hydrolize cellulose into glucose, by the action of some bacteria that they contain. - Oils and fats are triglyceride esters, since they form from the combination between trihydric alcohol and three molecules of fatty acids. Saponification: The hydrolysis of esters iin the presence of strong alkali (NaOH) or (KOH) to form sodium or pottasium salt of the fatty acid (soap). - The iodine number: The amount of iodine in grams needed to saturated 100 grams of the triglyceride. - The iodine number of stearic acid = zero because it is saturated. - rancidity of oils or fat: A chemical reaction that produced a change in colour, odour and taste of fats and oil as a result of oxidation . - Artificial fats are produced from the hydrogenation of vegetable oils. - Margarine (butter substitutes) are produced by mixing hydrogenated oil with milk. - Proteins are natural polymers, as they are produced from the condensation of unlimited number of amino acids. They combine together forming a chain of polypeptide. Amino acid is the basic unit of protein molecule. - Amino acids are considered as the amino derivatives of organic acids, since a hydrogen atom in the alkyle group of organic acid is replaced with an amino group. - eg: Glycine is amino acetic acid. - Amino acids are amphoteric compounds since they react with an acid as a base and react with the base as an acid to give salt and water. - The isoelectric point is the pH value at which the amino acid exists in the form of dipolar ion and precipetate. - The amino acids exist in the neutral medium in the form of dipolar ion, in alkaline medium they are presented as anions and in acidic medium as cations. - The essential amino acids are ten in number. They must be taken in diet since they cannot be synthesized in the body, while the non essential amino acids are not essential to be taken in diet, as they are synthesized in the body.