Carbohidratos y Clasificación

Carbohydrates

• Carbohydrates are the most abundant biomolecules on Earth's surface (75%).
• A typical carbohydrate is a hydrocarbon chain with various alcohol groups (-OH) and a more oxidized carbon (carbonyl, 'keto', C=O).
• They are formed in plants from CO2 and in animals from amino acids.
• They are an immediate source of energy (e.g., glucose) for the brain and red blood cells.
• They make up 0.3% of the organism's composition.
• A daily intake of approximately 380g provides 1520 kcal (57.3% from carbohydrate combustion, alongside lipids and proteins).

Classification of Carbohydrates

• Monosaccharides: These are the basic units, containing 3-8 carbon atoms. They cannot be hydrolyzed into simpler sugars. Examples include fructose, glucose, and galactose.
• Oligosaccharides: Formed by connecting monosaccharides. Disaccharides (2 units) like lactose and maltose, and trisaccharides (3 units) like raffinose and maltotriose are examples. (2-10 units).
• Polysaccharides: Composed of numerous monosaccharide units (>10). These can be linear or branched chains. Examples include homopolysaccharides (having one type of sugar) like starch, glycogen and cellulose, and heteropolysaccharides (having multiple sugars).

Monosaccharides: Classification

• Monosaccharides are classified by the number of carbon atoms (trioses, tetroses, pentoses, hexoses, heptoses, octoses).
• The most biologically important are hexoses, followed by pentoses.
• The nature of these molecules can be grouped as aldoses (aldehyde groups) and ketoses (ketone groups).
• The presence of asymmetric carbons results in stereoisomers, which are different spatial arrangements of the same molecule.

Isomerism

• Isomers are compounds with the same molecular formulas but different atom arrangements.
• Structural isomers: These have different structural arrangements (e.g., butane and methylpropane).
• Stereoisomers: These have different spatial arrangements. Further divided into:
  • Enantiomers: Non-superimposable mirror images (e.g., (R)- and (S)- isomers).
  • Diastereomers: Non-superimposable, non-mirror images (e.g., cis- and trans- isomers).
  • Conformational isomers: Different spatial arrangements around single bonds (e.g., different arrangements around a straight carbon chain).

D-Aldoses and D-Ketoses

• D-Aldoses and D-Ketoses are various forms of monosaccharides, differentiated by the position of the carbonyl group. They exist as a chain of carbons that differ in the location of their hydroxyl groups.
• The most common examples: D-glyceraldehyde, D-erythrose, D-ribose, D-arabinose, D-xylose, D-allose, D-altrose, D-glucose, D-mannose, D-gulose, D-idose, D-galactose, and D-talose.
• D-Ketoses are differentiated, having a ketone group versus an aldehyde group. These examples: Dihydroxyacetone, D-erythrulose, D-ribulose, D-xylulose, D-psicose, D-fructose, D-sorbose, and D-tagatose.

Derived Monosaccharides

• Alditols: Formed by reducing the carbonyl group to an alcohol group. Examples: sorbitol, mannitol, and ribitol.
• Deoxy Sugars: Formed by removing a hydroxyl group. Examples: 2-deoxyribose and fucose.
• Amino Sugars: Formed by replacing a hydroxyl group with an amino group. Examples include glucosamine and galactosamine.
• Acidic Sugars: Oxidation of the terminal carbon to a carboxyl group (creating an acid). Examples: glucuronic acid, and gluconic acid.

Disaccharides

• Formed when two monosaccharides join via a glycosidic bond. The most biologically relevant examples are sucrose, lactose, and maltose.
• Important disaccharides include lactose (galactose + glucose), sucrose (fructose + glucose), and maltose (glucose + glucose).

Polysaccharides

• Large polymers of monosaccharides – starch, glycogen, cellulose, and chitin are all polysaccharides.
• Starch: A storage polysaccharide in plants, consisting of amylose (linear) and amylopectin (branched) chains of glucose.
• Glycogen: A storage polysaccharide in animals, highly branched for rapid glucose mobilization.
• Cellulose: A structural polysaccharide in plants, consisting of linear chains of glucose with beta(1-4) linkages. It is indigestible to humans.
• Chitin: A structural polysaccharide in arthropods and fungi, containing N-acetylglucosamine units.

Esta prueba explora la composición y clasificación de los carbohidratos, que son biomoléculas esenciales en la naturaleza. Aprenderás sobre sus tipos, desde monosacáridos hasta polisacáridos, y su papel crucial como fuente de energía. Además, se discutirán datos relevantes sobre la ingesta diaria recomendada.