POLYSACCHARIDES

Polysaccharides

also called glycans, these are complex carbohydrates with high molecular weight.​

Polysaccharides

these are composed of abundant monosaccharides units combined together through loss of water molecules.​

Polysaccharides

• length of the polymer chain – less than a hundred monomer units up to million monomer units.​

• Monomeric subunits are covalently joined via glycosidic linkages (either α or β configuration)

• Exists either as continuous straight chains (unbranched) or highly branched polymers with varying degrees of branching.

Polysaccharides

these are non-reducing sugars and are not sweet-tasting

• examples are starch, cellulose, glycogen, chitin, and chitosan

Polysaccharides

• Serves as mobile and reserve carbohydrate reserves in both animal cells (glycogen) and plant cells (starch).

• Provides essential tensile strength, shape, and mechanical support (e.g., cellulose in plant cell walls, chitin in arthropods and fungi).

Polysaccharides

Functions in cell-cell recognition, immune modulation, extracellular matrix cohesion, and joint lubrication (hyaluronic acid, heparin)

Heteropolysaccharides (Heteroglycans)

composed of two or more distinct types of monosaccharide residues or sugar derivatives (often containing repeating disaccharide subunits of amino sugars and uronic acids)

• Heparin (natural anticoagulant)

• Hyaluronic Acid (synovial fluid, vitreous humor, ECM)

Starch

• The main storage homopolysaccharide of α-linked D-glucose in plants; known historically as amylum

• Insoluble in cold water; when heated in water, granules hydrate and swell to form a colloidal, viscous opalescent solution.

Starch

• Non-reducing sugar; forms no osazone crystals.

• Hydrolyzed enzymatically into disaccharide maltose, and completely hydrolyzed by strong acid into monosaccharide D-glucose

• Yields a characteristic deep blue or dark blue coloration upon treatment with iodine reagent

Achromatic Point

The definitive point during starch hydrolysis at which the solution ceases to produce any color change with iodine (indicates conversion to achrodextrin, maltose, and glucose).

Starch

Main source of carbohydrates for humans in diet and other animals. Present in daily diet in the form of bread, rice, potatoes, corn, etc. and used in confectionery and bakery to make pancakes, cereals, noodles, pasta, tortilla etc. It is also used in the beverage industry to make malt.

Amylose, Amylopectin

Two kinds of starch granules molecules

Amylose

• Straight chain polymer

• Connected exclusively by α-(1→4)- glycosidic linkages (the same linkage found in maltose).

• Readily hydrolyzed by amylases along the linear chain.

Amylose

• Moderately water-soluble; in boiling water, the amylose fraction selectively dissolves into the aqueous solution.

• Foods with high amylose content exhibit a significantly lower glycemic index (GI

Amylose

A type of distinct structural polymer of a native plant starch granule that forms an inclusion complex producing a dark blue / deep blue color.

Amylopectin

• Highly branched polymer composed of thousands of D-glucose residues.

• Linear chains contain α-(1→4)-glycosidic bonds, with branch points formed by α-(1→6)- glycosidic bonds occurring every 24 to 30 glucose units.

Amylopectin

• Insoluble in water; forms the outer envelope of the starch granule. When boiled, it swells to form a thick, colloidal viscous gel.

• Rapidly digested due to multiple branch ends, producing a high glycemic index (GI).

Amylopectin

A type of distinct structural polymer of a native plant starch granule that yields a violet to reddish-brown color with iodine

Amylolytic Enzymes

• α-Amylase (Endoamylase)

• β-Amylase (Exoamylase)

• α-(1→6)-Glucosidase (Debranching Enzyme)

• Glucoamylase

• Dextrins

α-Amylase (Endoamylase)

An amylolytic enzyme, cleaves internal α-(1→4) bonds randomly within both amylose and amylopectin, rapidly yielding maltose, maltotriose, and α-limit dextrins.

β-Amylase (Exoamylase)

An amylolytic enzyme, cleaves successive maltose units from the non-reducing ends of starch chains. In amylopectin, it halts 2–3 residues before an α-(1→6) branch point, producing dextrin molecules (β-limit dextrins).

α-(1→6)-Glucosidase (Debranching Enzyme)

An amylolytic enzyme, specifically cleaves the α-(1→6) branch linkages at branch points in dextrins, allowing complete degradation.

Glucoamylase

An amylolytic enzyme, cleaves terminal α-(1→4) and α-(1→6) bonds from non-reducing ends, releasing free D-glucose

Dextrins

An amylolytic enzyme, intermediate degradation oligosaccharides formed during the partial hydrolysis (dextrinization) of starch. Extensively utilized commercially in the manufacture of adhesives, paper sizing, and mucilages.

Amylose

acts physiologically as a resistant starch (RS), categorized as a functional type of insoluble fiber so it is not digested but fermented in the gut by some strains of healthy bacteria (bifidobacteria, lactobacillus, limosilactobacillus)

RS1

• Starch physically trapped within fibrous plant cell walls and seeds.

• The gut cannot access these molecules mechanically.

• Found in: seeds, whole grains, and legumes.

RS2

• Highamylose starch that is indigestible in its native raw state due to dense crystalline packing.

• Found in: raw unripe potatoes, green bananas, and plantains.

• When cooked, it gelatinizes and becomes digestible

RS3

• Formed when RS1 or RS2 starchy foods are cooked (gelatinized) and then allowed to cool.

• Retrograded amylose recrystallizes into a digestion-resistant matrix. Can be reheated below 130°F (54°C) without losing its resistant structure.

• Found in: boiled and cooled potatoes, chilled cooked rice

RS4

• Artificially synthesized or chemically cross-linked/esterified starches (e.g., "hi-maize resistant starch").

• Not recommended by natural health advocates as it lacks the physiological behavior of organic whole-food amylose

High-Amylose Foods

• Seeds, nuts, and legumes (soaking recommended prior to cooking to degrade antinutrients such as lectins).

• Sprouted or 100% whole-grain breads.

• Non-GMO corn, whole oats, and barley.

• Green bananas and plantains (unripe and cooked varieties have the highest amylose content).

• Raw starches and flours (e.g., arrowroot flour, raw unmodified potato starch in smoothies/soups).

• Cooked and subsequently cooled rice.

• Root vegetables and tubers: cassava, lesser yam, boiled and cooled potatoes, and tapioca pearls

Low-Amylose Foods

• Standard ripe fruits (excluding green bananas and plantains).

• Above-ground non-starchy vegetables.

• Animal protein: meat, fish, and poultry.

• Processed breads, commercial tortillas, and refined sugary snacks

Amylopectin

Represents the primary storage molecule produced via photosynthesis. Chlorophyll converts sunlight, carbon dioxide, and water into glucose, which is assembled into amylopectin for energy storage

Amylopectin

Ingested amylopectin is rapidly cleaved by salivary and pancreatic α-amylases into maltose and glucose. Glucose fuels cellular ATP production, tissue repair, muscle movement, and organ function. Excess glucose is polymerized into glycogen in liver and muscle cells or stored as fat.

High-Amylopectin Foods

Short-grain sticky rice, refined white bread, bagels, white potatoes (russet), commercial cookies, crackers, pretzels, instant oatmeal, puffed rice, cornflakes, and processed rice cakes

Low-Amylopectin Foods

Long-grain rice, whole oats, quinoa, sweet potatoes, bananas, whole wheat, barley, rye, beans, and legumes.

Glycogen

• ranched-chain polymer like amylopectin, but with more frequent branching (about every 10 residues / 8–12 units).

• Responsible for the characteristic sweet taste of fresh liver

• Also found in mollusks (oysters and other sea shells), sweet corn, yeasts, and fungi/molds.

Glycogen

• The primary glucose storage homopolysaccharide in animals and humans, historically called animal starch

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Glycogen

• Soluble in water, forming an opalescent, colloidal solution.

• Non-reducing carbohydrate

• Does not form osazone crystals.

Glycogen

• Produces a distinct red to red-brown color upon reaction with iodine.

• Complete acid hydrolysis proceeds through progressive dextrin intermediates

Glycogenesis, Glycogenolysis

Metabolic Pathways of Glycogen (2)

Glycogenesis

formation of glycogen from glucose and stores in the liver for use by the body at a later time

Glycogenolysis

process by which glycogen, the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into glucose to provide immediate energy and to maintain blood glucose levels during fasting

Glycogenolysis

Governed by two central regulatory enzymes:

• phosphorylase kinase

• glycogen phosphorylase

Glycogenolysis

Stimulated primarily in the liver by glucagon (secreted during fasting) and in muscle/liver by epinephrine (adrenaline) during stress and physical exertion.

Glycogenolysis

the biochemical pathway in which glycogen breaks down into glucose-1-phosphate and glucose

Chitin

• Major structural component of the exoskeletons of invertebrates (insects and crustaceans)

• occurs in cell walls of algae, fungi and yeasts

• Composed of units of N-acetyl-β-D-glucosamine joined by β-(1→4)-glycosidic bonds

Chitin

used as structural material in arthropod exoskeletons, fungal cell walls, and surgical thread.

Biomedical Applications of Chitin

• Wound Dressings:

  • Protects wound skin from contamination and infection,

  • increases dermal regeneration,

  • accelerates wound healing,

  • prevents bacteria infiltration,

  • and avoids water loss.

• Surgical Threads:

  • Strong, flexible, and decomposed naturally after the wound heals.

Anticoagulation

essential for open-heart surgery and kidney dialysis which prevents blood from clotting during sugery

Sulfated chitin derivatives

have good anticoagulant activity

Chitosan

A modified carbohydrate polymer derived from the shells of crustaceans (crab, shrimp, lobster, cuttlefish, squid, etc.) via deacetylation.

Chitosan Uses

• Pharmaceuticals:

  • Gels and hydrogels (controlled, sustained drug release).

  • Films and membranes (controlled drug release).

  • Emulsions (microspheres, microcapsules for sustained release, increased bioavailability, and mucoadhesion).

  • Targeted cancer therapy (retention and accumulation of drug in tumor).

  • Systems for controlled delivery/release of peptide drugs, vaccines, and genes

• Medicine and Biomedicine:

  • Wound dressings, wound treatment, and bandages. Sutures and surgical implants

  • Hemodialysis membranes and biomedical device coatings.

  • Hemostasis and anticoagulants.

  • Tissue engineering: scaffolds for tissue engineering and artificial skin grafts.

• Other Uses:

  • Agriculture, textile industry, and wastewater treatment

Heteropolysaccharides

Heteroglycans

Heteropolysaccharides

• A polymer consisting of monosaccharide residues bonded together by glycosidic linkages

• Linkages can be between different monosaccharides (branched polymer) or between the same repeating disaccharide units (linear polymer).

Heteropolysaccharides

• Naturally occurring heteropolysaccharides often have peptides, proteins, and lipids attached to them

  • Heparin, Hyaluronic Acid

Heparin

• Natural blood thinner / anticoagulant.

• Accelerates the inactivation of thrombin and other blood clotting agents (decreases clotting ability to prevent harmful clots).

Heparin

• Composed of repeating glucuronic acid and glucosamine (sulfated).

• Discovered by McLean in 1916.

Heparin

• Strong electromagnetic compound; strongest acid in the human body.

• Present in all tissues containing mast cells.

• Commercially prepared from beef lung and pig (porcine) intestinal mucosa.

Heparin

• Prevents blood clotting in heart and lung conditions.

• Used during open-heart surgery, bypass surgery, kidney dialysis, and blood transfusions.

• Used in low doses to prevent blood clot formation in bedridden patients or those undergoing surgery.

• Used to diagnose and treat disseminated intravascular coagulation (DIC)

Hyaluronic Acid

• A glycosaminoglycan found in extracellular tissue space, the synovial fluid of joints, and the vitreous humor of the eyes.

• Acts as a binding, lubricating, and protective agent.

Hyaluronic Acid

Composed of repeating polymeric disaccharides of D-glucuronic acid and N-acetyl-D-glucosamine linked by a glucuronidic β-(1→3) bond.

Restylane, Restylane-L, Perlane

Commercial brands of Hyaluronic Acid

Hyaluronic Acid

• Anti-aging and anti-wrinkle skin care (Hyaluronic Acid Serum).

• Soothing moisturizer formulated with Vitamin C + E + L-Arginine.

• Restores and rejuvenates skin for a youthful appearance.

• Rehydrating lotion gel containing lavender oil and witch hazel extract.

• Draws moisture from the environment and replenishes essential skin nutrients.

• Used in wrinkle skin treatments and dermal fillers