Carbohydrates: Structure and Functions

Study Notes

Macronutrients include carbohydrates, proteins, and fats required in large quantities.
They are vital for bodily formation, growth, and energy provision.
Macronutrients significantly contribute to body weight.

Carbohydrates are essential biomolecules found in all living organisms.
Composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio, with the general formula (CH2O)n.
Common sources include grains, vegetables, fruits, and dairy products.

Physical Properties:
- Solubility: Monosaccharides and disaccharides are water-soluble; polysaccharides are less soluble and cellulose is insoluble.
- Sweetness: Sweetness varies among monosaccharides; fructose is the sweetest, followed by sucrose, glucose, and galactose.
- Optical Activity: Carbohydrates can rotate polarized light, aiding in sugar identification.
- Crystallinity: Monosaccharides form crystalline structures; polysaccharides are generally amorphous.
Chemical Properties:
- Hydrolysis: Disaccharides/polysaccharides can be broken down into monosaccharides with water; enzymatic or acidic conditions facilitate this.
- Dehydration Synthesis: Monosaccharides combine to form larger carbohydrates by removing water, catalyzed by enzymes.
- Oxidation: Carbohydrates can be oxidized during cellular respiration to produce ATP, with tests available to detect reducing sugars.
- Fermentation: Sugars can undergo fermentation.

Carbohydrates provide energy and help regulate blood glucose.
They spare proteins from being used for energy.
Involved in biological recognition processes through glycoproteins and glycolipids.
Constituent of nucleic acids and structural components of plant and bacterial cell walls.
Serve as flavor and sweeteners, and dietary fiber.

Monosaccharides: Simplest form, include glucose (primary energy source), fructose (found in fruits), and galactose (part of lactose).
Disaccharides: Formed from two monosaccharides; examples include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose).
Polysaccharides: Complex carbohydrates, categorized into:
- Storage Polysaccharides:
  - Starch (plant glucose storage, found in potatoes and rice).
  - Glycogen (animal glucose storage in liver and muscles).
- Structural Polysaccharides:
  - Cellulose (plant cell wall component).
  - Chitin (found in fungal cell walls and insect exoskeletons).