What is Sucrose? Definition, Structure, & Examples

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Sucrose Definition

Sucrose is a disaccharide with the molecular formula C12H22O11 that is produced by the combining of glucose and fructose in some plants (e.g. sugarcane); common table sugar. 

Sucrose has been crystallised and utilised from the dawn of time. Andreas Marggraf, a German scientist who lived from 1709 to 1782, was credited with discovering sucrose in 1747. (Note that Marggraf is also credited with being the first to separate glucose from raisins, which he did in 1747.)

Sucrose is derived from the French sucre, which is taken from the Latin saccharum (which means “sugar”). It is indicated by the suffix –ose that it is a “sugar.” William Miller, an English chemist, invented the phrase.

Saccharose was the name given to it by French scientist Pierre Eugène Marcellin Berthelot (1827–1907). Berthelot was also the one who gave the sugars galactose and lactose their modern names.

What is Sucrose?

Sucrose is a kind of disaccharide carbohydrate that also includes lactose and maltose. Carbohydrates are a large group of biomolecules that are categorised according to their saccharide content. A disaccharide, in specifically, is a carbohydrate composed of two monosaccharides joined by a glycosidic bond (glycosidic linkage).

Sucrose is a crystalline white substance. The molar mass of this substance is 342.30 gmol-1. It has a melting point of 186 degrees Celsius. It is water soluble. Sucrose has the same general formula as lactose and maltose: C12H22O11. Sucrose, on the other hand, is a disaccharide that consists of one glucosyl and one fructosyl unit. They’re connected by a (1→2) glycosidic bond. This indicates that the carbon(C)-1 on the glucosyl unit and C2 on the fructosyl unit form a bond.

Sucrose vs Lactose vs Maltose

The three most prevalent dietary disaccharides are sucrose (table sugar), lactose (milk sugar), and maltose (malt sugar). The three disaccharides, as previously stated, have the identical chemical formula: C12H22O11. Glucose is present in all three. Maltose is a substance made up of two glucose units.

However, just one glucose unit interacts with another monosaccharide in lactose and sucrose, resulting in galactose and fructose, respectively. The α-(1,4) glycosidic link connects the two sugars in maltose, i.e. C1 and C4. Lactose contains a β-(1,4) glycosidic link between galactose C1 and glucose C4. A α-(1,2)-βbond may form between C1 of glucose and C2 of fructose in sucrose.

Lactose and maltose are both reducing sugars; sucrose, on the other hand, is a non-reducing sugar. Because one of the monosaccharide components might offer a free aldehyde group, maltose and lactose are reducing sugars. The glycosidic link develops between the reducing ends of the two monosaccharide components in the case of sucrose. As a result, sucrose could no longer combine with other saccharide units.

Foods sweetened with sugar derived from sugar cane and sugar beet provide the majority of dietary sucrose. Lactose is plentiful in milk and dairy products, but maltose is typically derived from the digestion of starchy foods. Specific digestive enzymes, such as sucrase, maltase, and lactase, help in the digestion of these sugars. These enzymes are found on the outside of the epithelial cells that lining the small intestine in humans.

Sucrase aids in the digestion of sucrose. Lactase is a digestive enzyme that assists in the digestion of lactose. Maltase aids in the digestion of maltose. The bond between the two monosaccharide components is cleaved by these enzymes.

Sucrose Metabolism

A glycosyl unit and a fructosyl unit are linked in sucrose by a (1→2) glycosidic bond. Glucose can be alpha-pyranose or beta-pyranose. Fructose comes in a variety of isomers. Only one kind of each comes together to produce sucrose. Water is released when two monosaccharides are joined together.

Plants and cyanobacteria are the primary biosynthesisers of sucrose. To make sucrose, they need precursors like uridine diphosphate (UDP)-glucose and fructose 6-phosphate. Sucrose-6-phosphate synthase is a plant enzyme that catalyses the transfer of the hexosyl group from UDP-glucose to fructose 6-phosphate.

Sucrose is the predominant sugar in certain plants, whereas fructose is the primary sugar in others. Sucrose is the source of their energy. It may be found in a variety of plant components, including roots, fruits, and nectar. Plants utilise nectar to attract specific insects, such as bees, so that pollination may occur. Sucrose is derived from sugarcane and sugar beet plants for human use.

Saccharification is the process of breaking down complex carbohydrates into simpler ones. Dehydration synthesis is the polar opposite of this. The condensation reaction forms a glycosidic link between the joining sugars in dehydration synthesis, resulting in complex carbohydrates and the release of water. Hydrolysis, which utilises water molecules to dissolve the glycosidic bond and release the sugar components, is used in saccharification.

Consumption of dietary sucrose causes the small intestine to release sucrase in humans. The enzyme breaks down sucrose into glucose and fructose, which are subsequently absorbed by enterocytes (intestinal cells), released into the circulation, and then absorbed by cells in diverse organs such as the liver, kidney, and muscle.

The hydrolysis of sucrose is further aided by gastric acidity, as the acid in the stomach may dissolve acetal bonds. The enzyme invertase catalyses the digestion of sucrose in various animals and microorganisms.

Sucrose and Metabolic Disorders

Sucrose intolerance, also known as sucrase-isomaltase deficiency or genetic sucrase-isomaltase deficiency (GSID), is a disease in which the metabolism of sucrose is disrupted. This is caused to a deficiency or absence of the functioning enzyme sucrase-isomaltase. A mutation in the genes that code for this enzyme might be the cause of this disease. Irritable bowel syndrome and ageing have also been linked to it.

Sucrose consumption causes a fast rise in blood glucose levels. A diet high in sugar over an extended period of time may raise the risk of type 2 diabetes. Diabetes mellitus is characterised by a shortage of insulin, either relative or absolute, resulting in uncontrolled glucose metabolism. Diabetes type 2 develops in adults and is characterized by an excess of sugar in the bloodstream and urine.

Biological Importance and Functions of Sucrose

Plants and cyanobacteria generate sucrose naturally. Sucrose is found in fruits, nectar, and the roots of plants. Sucrose is synthesised by plants during photosynthesis and stored for later use. Insects, particularly bees, are drawn to nectar. While functioning as pollinators, the bees eat their nectar.

They also make honey from the sugar that has accumulated. Plants provide sucrose to animals and microorganisms (apart from starch). Humans extract and refine sucrose for use in food preparation. It is usually referred to as table sugar and is used to sweeten foods and beverages.

Monosaccharide components of sucrose are consumed by organisms. Sucrose delivers glucose and fructose to the body through digestion or hydrolysis. Glucose is very important since it is preferred for use in energy metabolism. It’s the monosaccharide that the cell utilises to make ATP through substrate-level phosphorylation (glycolysis) and/or oxidative phosphorylation (involving redox reactions and chemiosmosis).

When glucose is insufficient and the metabolic energy demand is high, fructose functions as an alternate metabolite to provide energy. Glycogen synthesis, triglyceride synthesis, free fatty acid synthesis, and gluconeogenesis are all key metabolic processes that fructose enters.

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