Carbohydrates and Monosaccharides Quiz

Study Notes

Carbohydrates are organic molecules made up of carbon, hydrogen, and oxygen.
They are essential for energy production, storage, and carbon supply for protein and fat synthesis.
Carbohydrates also play a role in the structure of nucleic acids like DNA and RNA.

Simple carbohydrates with polyhydroxy aldehydes or ketones, with the formula (C-H2-O)n.
Examples include trioses (three carbons), tetroses (four carbons), pentoses (five carbons), and hexoses (six carbons).
Classified as aldoses or ketoses based on their functional group (aldehyde or ketone).

Molecules with the same chemical formula but differing in the position of hydroxyl groups on asymmetric carbons.
Enantiomers are mirror images of each other (e.g., D-glucose and L-glucose).
Epimers differ in the position of only one hydroxyl group on an asymmetric carbon (e.g., D-glucose and D-galactose).

Monosaccharides can form ring structures through a reaction between the aldehyde or ketone group and a hydroxyl group within the molecule.
This process creates anomeric carbons, which are essential for glycosidic bond formation.

Sugar alcohols are formed by reducing the aldehyde or ketone group to a hydroxyl group (e.g., sorbitol). Excess glucose can lead to sorbitol accumulation, causing issues like cataracts and neuropathy.
Sugar acids are created by oxidizing the aldehyde group or terminal carbon hydroxyl to a carboxylic group (e.g., gluconic acid and glucuronic acid). Glucuronic acid plays a role in drug metabolism through conjugation.
Amino sugars are formed by replacing the OH group on the third carbon with an amino group (e.g., glucosamine).

Formed by combining two monosaccharides through glycosidic bonds.
Important examples include lactose (galactose + glucose), sucrose (glucose + fructose), maltose (glucose + glucose), and lactulose (galactose + fructose).
Lactulose is a synthetic disaccharide used as a laxative and ammonia removal agent from the gastrointestinal tract.

Sugars with a free anomeric carbon can act as reducing agents, causing the reduction and color change of Benedict's or Fehling's reagent.
This property is used to diagnose the presence of glucose in diabetic patients and lactose in lactating women's urine.

Glycogen is a branched polysaccharide of glucose units, primarily stored in the liver and skeletal muscles. It serves as the main carbohydrate storage for the body.
Starch is a glucose polymer found in plants, a major source of dietary carbohydrates. It consists of amylose (linear) and amylopectin (branched) molecules.
Both glycogen and amylopectin are branched chain polysaccharides, with glucose molecules linked by a (1 - 4) linkages and branches connected by a (1 - 6) linkages.
Humans and animals can digest starch through the hydrolysis of amylose and amylopectin by the enzyme amylase.

A structural polysaccharide found in plants, primarily responsible for their rigidity and cell walls.
Most animals, including humans, cannot digest cellulose due to the absence of the necessary enzymes.
Exceptions include some herbivores and certain gut bacteria.

Carbohydrates can be linked to non-carbohydrate molecules through glycosidic bonds.
Examples:
- Purines and pyrimidines in nucleotides of nucleic acids
- Proteins in glycoproteins and proteoglycans
- Lipids in glycolipids