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  • Carbohydrates are biomolecules that are composed of carbon, hydrogen

  • and oxygen atoms in the ratio of 1:2:1.

  • We can represent the proportion of these elements within carbohydrate molecules

  • with the formula CH2O.

  • Most carbohydrates are characterized as either monosaccharides, disaccharides or polysaccharides.

  • The termsaccharideis just another word for sugar.

  • The prefixes mono, di and poly refer to the number of sugars in the molecule.

  • Monomeans one,

  • so a monosaccharide is a carbohydrate made of one unit of sugar.

  • The prefixdimeans two,

  • so a disaccharide is a carbohydrate made of two units of sugar.

  • Andpolymeans many,

  • so a polysaccharide is made of many sugar units bonded together.

  • Let’s talk about monosaccharides first.

  • Monosaccharides are the building blocks, or monomers, of all carbohydrates.

  • Common monosaccharides include glucose, fructose, and galactose.

  • Glucose is by far the most abundant monosaccharide.

  • It is water soluble, easily transported through an organism,

  • and is the energy source for cellular respiration and the production of ATP.

  • Fructose is the primary monosaccharide found in fruits and plants,

  • and galactose is the primary monosaccharide found in milk.

  • All of these monosaccharides are six carbon sugars with the chemical formula C6H12O6.

  • They can be depicted chemically as either straight chains or rings.

  • Disaccharides are formed when monosaccharides are joined together

  • through dehydration reactions forming glycosidic linkages.

  • Common disaccharides include maltose, which is made up of two glucose molecules;

  • sucrose (also known as table sugar),

  • which is made up of glucose and fructose;

  • and lactose (or milk sugar) which contains glucose and galactose.

  • Polysaccharides are formed when glucose monomers link together to form long chains.

  • These long chains of glucose units are ideal for storing energy.

  • The chains can be straight or branched.

  • Plants store energy in the form of amylose, which has straight chains, or amylopectin, which is branched.

  • Animals differ from plants in that they store energy in the form of glycogen,

  • which is a highly branched polysaccharide that can be broken down quickly to supply energy to tissues.

  • Other polysaccharides such as cellulose, chitin and peptidoglycan

  • serve as structural molecules in organisms.

  • The most abundant polysaccharide is cellulose.

  • Cellulose is a straight chain polymer of glucose like amylose,

  • but it differs in the configuration of the bonds between the glucose units.

  • Most organisms are unable to break these bonds and cannot use cellulose as a source of energy.

  • Instead cellulose is used to add strength to plant cell walls.

  • Chitin is a structural polysaccharide found in animals and fungi.

  • It makes up the exoskeleton of insects and

  • crustaceans. Its unique properties are a result of chitin having amino groups attached to its sugar monomers.

  • Peptidoglycans are complex polysaccharides found in the cell walls of bacteria.

  • The macromolecule is both flexible and rugged due to its structure.

  • Each monomer of the polysaccharide has a peptide chain attached to it.

  • Often, we refer to carbohydrates as being either simple sugars or complex carbohydrates.

  • Monosaccharides and disaccharides are commonly referred to as simple sugars.

  • The term complex carbohydrates refers to the polysaccharides.

Carbohydrates are biomolecules that are composed of carbon, hydrogen


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B2 中高級

碳水化合物 (Carbohydrates)

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    Yrchinese 發佈於 2021 年 01 月 14 日