Polysaccharides Overview

Polysaccharides

• Carbohydrate polymers composed of multiple monosaccharide units connected by glycosidic linkages.
• Homopolysaccharides consist of a single type of monosaccharide (e.g., starch, glycogen, cellulose); yield glucose upon hydrolysis.
• Heteropolysaccharides contain multiple types of monosaccharides, often referred to as glycosaminoglycans (GAGs).
• Examples of heteropolysaccharides include hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparin, heparan sulfate, and keratan sulfate.

Homopolysaccharides

• Starch

  • Main carbohydrate storage in plants; major dietary source for humans.
  • Major food sources are potatoes, rice, corn, and wheat.
  • Composed of two polysaccharides: amylose (linear) and amylopectin (branched).

• Glycogen

  • Primary carbohydrate storage in humans and animals; structure consists of glucose polymer with alpha links.
  • Most abundant in liver and muscle cells, accounting for 8-10% of liver weight and 2-3% of muscle weight.

Heteropolysaccharides

• Chondroitin Sulfate

  • Essential structural component in cartilage, enhancing its resistance to compression.
  • Plays a role in nutrient delivery to joint cartilage and in cartilage repair.

• Dermatan Sulfate

  • Found in skin, blood vessels, heart valves, tendons, and lungs; important for skin integrity.
  • Involved in coagulation, cardiovascular health, cancer progression, wound healing, and fibrosis.

• Heparin and Heparan Sulfate

  • Act as anticoagulants; contain D-glucuronic acid found in mast cells, important for inflammation and cell differentiation.

• Keratan Sulfate

  • Minor component of proteoglycans; located in the cornea, cartilage, and intervertebral discs.
  • Crucial for corneal development and maintaining tissue transparency.

Disaccharides

• Composed of two monosaccharides; hydrolysis yields two glucose molecules.

• Provide significant caloric intake in human diets; examples include lactose, maltose, sucrose, and cellobiose.

• Lactose

  • Known as milk sugar; a disaccharide of glucose and galactose linked via a beta bond.
  • Lactose intolerance can result from insufficient lactase, leading to digestive issues.

• Maltose

  • Contains two glucose units joined by an alpha bond; formed during starch hydrolysis.
  • Used as an energy source for plants and in beer production.

• Sucrose

  • Commonly known as table sugar; composed of glucose and fructose.
  • Produced in plants and serves as a major transportable energy source.

• Cellobiose

  • Composed of two glucose units linked via a glycosidic bond; not commonly found in nature.

Oligosaccharides

• Comprise 3 to 10 monosaccharides; often attached to glycoproteins and glycolipids in cell membranes.
• Nutritionally important oligosaccharides include raffinose and stachyose, found in beans and legumes.

Monosaccharides

• Classified by the number of carbon atoms: trioses (3), tetroses (4), pentoses (5), and hexoses (6).

• Pentoses and hexoses are the most common types found in living organisms.

• Glucose

  • Called dextrose or blood sugar; primary energy source for cells, especially brain and red blood cells.
  • Generates energy in cells with limited oxygen supply, such as those in the eyeball.

• Fructose

  • Also known as levulose or fruit sugar; highly abundant in fruits and vegetables.
  • Sweeter than sucrose, often used as a sweetener; provides energy for sperms after synthesis in the male reproductive system.

• Galactose

  • Necessary for synthesizing biomolecules, including lactose and glycolipids.
  • Galactosemia is a genetic disorder leading to its accumulation, which can cause liver damage and cognitive issues.

• Ribose and Deoxyribose

  • Pentose sugars present in genetic material; ribose in RNA and deoxyribose in DNA.

Explore the fascinating world of polysaccharides, which are carbohydrate polymers made from numerous monosaccharide units. This quiz covers the differences between homopolysaccharides and heteropolysaccharides, including examples like starch and hyaluronic acid. Test your knowledge on these essential components of biological systems.