Bioquímica Básica: Carbohidratos

General Information

• University: Universidad Veracruzana
• Faculty: Facultad de Medicina
• Region: Región Poza Rica - Tuxpan
• Program: Médico Cirujano
• Course: Bioquímica Básica
• Topic: Carbohidratos
• Instructor: QFB. Méd. Lucio Ivan Rodríguez Infante
• Date: Octubre 2024

Carbohydrate Concepts and General Properties

• A typical carbohydrate is a hydrocarbon chain with several alcohol groups (-OH) bonded to a more oxidized carbon (carbonyl, 'keto', C=O).
• Carbohydrates (sugars, saccharides, glycides) are abundant in terrestrial environments (approximately 75%).
• They constitute 0.3% of the organism.
• A daily intake of 380 grams provides 1520 kcal (57.3% from carbohydrate combustion, lipids, proteins).
• Carbohydrates are a principal source of immediate energy for most cells, particularly glucose for the brain and red blood cells.
• They are precursors for the synthesis of other biomolecules.
• They serve as energy reserves in tissues like liver and muscle.
• They also play structural roles in various tissues, including connective tissue.

Biological Functions and Related Concepts

• Carbohydrates provide immediate energy for most cells.
• They are involved in the biosynthesis of other biomolecules (anaplerotic pathways).
• They function as energy stores in organs like the liver and muscles.
• They contribute to the structure of various tissues, including connective tissues.
• Glucobiology: the study of carbohydrate functions in health and disease.
• Glucoma: a comprehensive analysis of an organism's sugars, both free and complex.
• Glucomica: a comprehensive study of glucome (genetic, physiological, pathological aspects).

Carbohydrate Classification

• Monosaccharides: consist of 3 to 8 carbon atoms.
  • They cannot be hydrolyzed into simpler sugars.
  • Examples: fructose, glucose, galactose.
• Oligosaccharides: formed by combinations of monosaccharides.
  • Disaccharides: two monosaccharide units (lactose, maltose).
  • Trisaccharides: three monosaccharide units (raffinose, maltotriose), etc. (2-10 units).
• Polysaccharides: comprised of numerous (>10) monosaccharide units.
  • These can be linear or branched chains.
  • This category includes homopolysaccharides (single monosaccharide) and heteropolysaccharides (multiple monosaccharides).

Monosaccharides: Classification

• Number of atoms: trioses, tetroses, pentoses, hexoses, heptoses, and octoses.
  • The most biologically important are hexoses, followed by pentoses.
• Chemical nature: carbonyl group
  • Aldoses (aldehyde group): at the end of the chain (aldohexoses).
  • Ketoses (ketone group): at a position other than the end.
• Stereoisomers: due to the presence of asymmetric carbons and optical activity.

Isomerism

• Isomers have the same molecular formula but different atomic arrangements.
• Structural isomers: different structural configurations.
• Stereoisomers: different spatial arrangements.
  • Diastereomers: Non-mirror image isomers.
  • Enantiomers: mirror image isomers that cannot be superimposed.
    • Conformational isomers: different spatial arrangements around single bonds.

Chirality and its Relation to Monosaccharides

• Carbon atoms with four different substituents are chiral or asymmetric.
• D- and L- designations for monosaccharides are based on the orientation of the chiral carbon furthest from the carbonyl group.
• Gliceraldehído is the simplest aldotriose with optical activity.
• Monosaccharides can exist in different stereoisomers due to varying configurations around the different chiral centers.

Series of D-Aldoses and D-Cetoses

• These are series of D-monosaccharides illustrating the branching of monosaccharides.
• The aldoses have different number of chiral carbons; the cetoses have less chiral centers.
• Examples given of aldoses and ketoses, including their names.

Anomería and Mutarotation

• Anomerism: results from the cyclic structure of monosaccharides; a and β forms of a given sugar.
• Mutarotation: the equilibrium between the α and β anomeric forms in solution.

Carbohydrate Derivatives

• Alditoles: formed by reduction of the carbonyl group of a carbohydrate.
  • Examples like D-sorbitol and D-manitol.
• Deoxy sugars: formed through the loss of hydroxyl groups.
  • Examples include 2-deoxyribose and L-fucose, which are relevant components of DNA and glycoconjugates, respectively.
• Amino sugars: amino group substitution for a hydroxyl group, commonly on the C-2 position.
  • Examples include glucosamine and galactosamine, relevant to glycoconjugates or to other molecules.
• Acidic sugars: oxidation of terminal carbon to a carboxyl group.
  • Derivatives contain a carboxyl group (-COOH).
  • Examples are uronic and aldonic acids, which are significant for detoxification, glycosaminoglycans, and other functions.

Disaccharides

• Formed by the condensation of two monosaccharides. Examples:
  • Lactose: galactose + glucose, found in milk.
  • Sucrose: fructose + glucose, commonly known as table sugar.
  • Maltose: glucose + glucose, a product of starch digestion.
  • Isomaltose: glucose + glucose with a different linkage
  • Other types exist with specific linkage types.

Polysaccharides

• Large, complex carbohydrates formed by many monosaccharide units.
  • Homopolysaccharides: made up of a single type of monosaccharide.
    • Starch: energy storage in plants (composed of amylose and amylopectin)
    • Glycogen: energy storage in animals
    • Cellulose: structural component in plant cell walls
    • Chitin: structural component in fungal cell walls and insect exoskeletons.
  • Heteropolysaccharides: made up of multiple types of monosaccharides.
    • These include specialized components of connective tissue, like glycosaminoglycans (GAGs).

Dietary Carbohydrates and Digestion

• Dietary fiber: indigestible polysaccharides found in plant foods, contributing to gut health.
• Nutrient absorption: different forms of carbohydrates are digested and absorbed in the digestive tract.

Diabetes Mellitus

• Definition, Prevalence, Risk Factors, Diagnosis, Auxiliaries, Treatment, Complications.

Diabetes in Pregnancy

• Pre-gestational diabetes, its prevalence, epidemiological factors, and its risks to both mother and child
• Gestational diabetes: intolerance to carbohydrates occurring first during pregnancy.
• Diagnosis and Classification: methods for diagnosing pregnancy-related diabetes
• Treatment guidelines and management.