Carbohidratos y Clasificación

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Questions and Answers

¿Cuál es la estructura típica de un hidrato de carbono?

  • Una cadena de aminoácidos unida por enlaces peptídicos.
  • Una cadena hidrocarbonada con grupos carbohidratos y amino.
  • Una cadena hidrocarbonada con varios grupos alcohol y un carbono más oxidado. (correct)
  • Una estructura lipídica con múltiples ácidos grasos.

¿Qué función principal tienen los hidratos de carbono en las plantas?

  • Son responsables de la formación de membranas celulares.
  • Sirven como forma de energía y almacenamiento. (correct)
  • Participan en la síntesis de proteínas.
  • Actúan como catalizadores en reacciones químicas.

¿Qué grupo funcional caracteriza a los hidratos de carbono?

  • Grupos carbonilo y alcohol. (correct)
  • Grupos ácido carboxílico.
  • Grupos éster.
  • Grupos amina.

¿Dónde se forman principalmente los hidratos de carbono?

<p>En las plantas durante el proceso de fotosíntesis. (D)</p> Signup and view all the answers

La cadena hidrocarbonada de un hidrato de carbono está generalmente asociada con qué tipo de grupos?

<p>Grupos alcohol y carbonilo. (B)</p> Signup and view all the answers

Flashcards

Carbohidratos

Moléculas orgánicas formadas por carbono, hidrógeno y oxígeno; son la principal fuente de energía para los seres vivos.

Función de los carbohidratos

Proporcionar energía a los seres vivos.

Estructura de un carbohidrato

Cadenas hidrocarbonadas con grupos alcohol (-OH) y un carbono oxidado (carbonilo).

Origen de los carbohidratos

Principalmente formados por las plantas.

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Ejemplos de Carbohidratos

Azúcar, almidón, o celulosa.

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Study Notes

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.

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