Carbohydrates Overview and Monosaccharides

Carbohydrates Overview

• Carbohydrates are a group of carbonyl compounds (aldehydes or ketones) that also contain several hydroxyl groups.
• General formula: (CH₂O)ₙ
• Carbohydrates can change in sore conditions, such as having less oxygen or more nitrogen.
• Isomers have the same formula but different structures.
• Fructose and glucose have the same formula (C₆H₁₂O₆).
• Carbohydrates are classified based on the number of units.
  • Monosaccharides, disaccharides, oligosaccharides, and polysaccharides
• The "-ose" suffix is added to names of carbohydrates.
• Carbohydrates can be classified by the type of carbonyl group (aldose or ketose) and number of carbons (triose, tetrose, etc.).

Monosaccharides

• Monosaccharides are the simplest carbohydrates.
• They are categorized as aldoses or ketoses, based on the carbonyl group's position.
• The number of carbons determines the specific name (triose, tetrose, pentose, hexose, etc.).
• Examples include glucose, fructose, galactose, ribose, and deoxyribose.
• Aldoses contain an aldehyde functional group on the first carbon.
• Ketoses contain a ketone functional group other than the first carbon.
• Some monosaccharides have isomers.
• Isomers have different structures.

Disaccharides

• Disaccharides are formed by joining two monosaccharides.
• A glycosidic bond forms between two monosaccharides.
• There are several types of disaccharides, including maltose, lactose, and sucrose.
• Each is made up of different monosaccharides and contains a glycosidic bond.
• Maltose is formed by combining two glucose molecules.
• Lactose is made up of glucose and galactose.
• Sucrose is made of glucose and fructose.

Polysaccharides (Complex Carbohydrates)

• Polysaccharides are polymers of monosaccharides.
• Polysaccharides have many functions in different organisms.
• Polysaccharides are important in energy storage and structural components.
• Starch, glycogen, and cellulose are examples of polysaccharides.
• Starch is found in plants and stored glucose for energy.
• Glycogen is an animal energy-storage polymer.
• Cellulose is a structural component in the plant cell wall.
• Starch can be divided into amylose and amylopectin.
• Both amylose and amylopectin are composed of glucose units.

Protein-Carbohydrate Structures

• Carbohydrates and proteins can sometimes occur together.
• Proteoglycans contain a high proportion of carbohydrate to protein.
• Glycoproteins contain a smaller carbohydrate proportion of protein.
• Glycoproteins have covalent oligosaccharides attached.
• Glycosylation affects protein function.

Digestion

• Digestion involves breaking down complex carbohydrates into simple sugars.
• Enzymes break down these bonds.
• Alpha-amylase is an example in the mouth.
• Glycosidase enzymes degrade glycosidic bonds.
• Starch is broken down into smaller sugars.
• Intestinal disaccharidases further break down disaccharides into monosaccharides.

Absorption

• Monosaccharides are absorbed into the bloodstream for use in metabolism.
• Different transporters, such as SGLT-1 and GLUT-2, are involved.
• Sodium dependent glucose cotransporter (SGLT-1) and GLUT-5, are examples of transporters.
• GLUT-2 helps in the absorption of glucose, fructose, and galactose.

Carbohydrate Metabolism

• Carbohydrates are central to energy metabolism.
• Blood glucose levels are usually maintained at a specific range for proper bodily function.
• Low or high blood glucose for an extended time can be problematic.