CHEMISTRY GLOSSARY

maltose    →   maltoza

Maltose (malt sugar) is a disaccharide which is obtained with hydrolytic decomposition of starch in the presence of enzyme amylase. Maltose is composed of two glucose molecules linked by an α(1→4)-glycosidic linkage. Maltose has an alpha acetal.

oligosaccharide    →   oligosaharid

Oligosaccharides are carbohydrates containing from three to ten monosaccharide units, each joined to the next by a glycoside bond.

carbohydrate    →   ugljikohidrat

Carbohydrates (often called carbs for short) are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis. They are also known as saccharides, a term derived from the Latin word saccharum for sugar. Carbohydrates are the most abundant class of compounds in the biological world, making up more than 50 % of the dry weight of the Earth’s biomass. Every type of food we eat can have its energy traced back to a plant. Plants use carbon dioxide and water to make glucose, a simple sugar, in photosynthesis. Other carbohydrates such as cellulose and starch are made from the glucose. Light from the sun is absorbed by chlorophyll and this is converted to the energy necessary to biosynthesize carbohydrates

The term carbohydrate was applied originally to monosaccharides, in recognition of the fact that their empirical composition can be expressed as C_x(H₂O)_y. Later structural studies revealed that these compounds were not hydrates but the term carbohydrate persists.

Carbohydrates are generally classed as either simple or complex. Simple sugars, or monosaccharides, are carbohydrates that can’t be converted into smaller subunits by hydrolysis. Complex carbohydrates are made of two (disaccharides) or more (oligosaccharides, polysaccharides) simple sugars linked together by acetal (glycosidic) bonds and can be split into the former by hydrolysis.

cellulose    →   celuloza

Cellulose, (C₆H₁₀O₅)_n, is a polysaccharide that consists of a long unbranched chain of glucose units linked by (1→4)-β-glycoside bonds. Nature uses cellulose primarily as a structural material to impart strength and rigidity to plants. Leaves, grasses, and cotton are primarily cellulose. The fibrous nature of extracted cellulose has led to its use in textile industry for the production of cotton, artificial silk, etc. Cellulose also serves as raw material for the manufacture of cellulose acetate, known commercially as acetate rayon, and cellulose nitrate, known as guncotton. Gunncotton is the major ingredient in smokeless powder, the explosive propellant used in artillery shells and in ammunition for firearms.

disaccharide    →   disaharid

Disaccharides are compounds in which two monosaccharides are joined by a glycosidic bond. A glycosidic bond to the anomeric carbon can be either α or β. For example, maltose, the disaccharide obtained by enzyme-catalyzed hydrolysis of starch, consists of two D-glucopyranose units joined by a 1,4’-α-glycoside bond. The "prime" superscript indicates that C-4 is not in the same ring as C-1. Unlike the other disaccharides, sucrose is not a reducing sugar and does not exhibit mutarotation because the glycosidic bond is between the anomeric carbon of glucose and the anomeric carbon of fructose.

fructose    →   fruktoza

Fructose (fruit sugar) is a ketohexose (a six-carbon ketonic sugar), which occurs in sweet fruits and honey. Glucose and fructose have the same molecular formula, C₆H₁₂O₆, but have different structures. Pure, dry fructose is a very sweet, white, odorless, crystalline solid. Fructose is one of the sweetest of all sugars and is combined with glucose to make sucrose, or common table sugar. An older common name for fructose is levulose, after its levorotatory property of rotating plane polarized light to the left (in contrast to glucose which is dextrorotatory). The polysaccharide inulin is a polymer of fructose.

glucose    →   glukoza

Glucose (grape sugar, blood sugar), C₆H₁₂O₆, is an aldohexose (a monosaccharide sugar having six carbon atoms and an aldehyde group). An older common name for glucose is dextrose, after its dextrorotatory property of rotating plane polarized light to the right. Glucose in free (in sweet fruits and honey) or combined form (sucrose, starch, cellulose, glycogen) is is probably the most abundant organic compound in nature. During the photosynthesis process, plants use energy from the sun, water from the soil and carbon dioxide gas from the air to make glucose. In cellular respiration, glucose is ultimately broken down to yield carbon dioxide and water, and the energy from this process is stored as ATP molecules (36 molecules of ATP across all processes).

Naturally occurring glucose is D isomers (OH group on the stereogenic carbon farthest from the aldehyde group, C-5, is to the right in the Fischer projection). Although often displayed as an open chain structure, glucose and most common sugars exist as ring structures. In the α form, the hydroxyl group attached to C-1 and the CH₂OH attached to C-5 are located on opposite sides of the ring. β-glucose has these two groups on the same side of the ring. The full names for these two anomers of glucose are α-D-glucopyranose and β-D-glucopyranose.

lactic acid    →   mliječna kiselina

Lactic acid is an acid produced as a result of anaerobic respiration in muscles and red blood cells, i.e. when glycogen is used as an energy source for respiration rather than oxygen. After production, it is converted back to glycogen in the liver. The build up of large amounts of lactic acid in the blood can lead to stress and toxic effects. High levels are usually a result of sustained, excessive exercise.

lactose    →   laktoza

Lactose (milk sugar) is a disaccharide comprising one glucose molecule linked to a galactose molecule by an β(1→4)-glycosidic linkage. Lactose has a beta acetal. Lactose is manufactured by the mammary gland and occurs only in milk (from 4 % to 7 %). Lactose intolerance is a common medical condition that results in diarrhea, abdominal pain, and flatulence and is caused by reduced or absent activity of enzyme lactase.

Like cellobiose and maltose, lactose is a reducing sugar. All reducing sugar undergo mutarotation in aqueous solution. The equilibrium mixture at 20 °C is composed of 62.7 % β-lactose (β-D-galactopyranosyl-(1→4)-β-D-glucopyranose) and 37.3 % α-lactose (β-D-galactopyranosyl-(1→4)-α-D-glucopyranose).

polyester    →   poliester

Polyesters are copolymers formed by condensation polymerization of dicarboxylic acid (terephthalic acid) and a dialcohol, also called a diol (ethylene glycol).