Podcast
Questions and Answers
What is the primary function of polysaccharides?
What is the primary function of polysaccharides?
Which structural feature distinguishes amylose from amylopectin?
Which structural feature distinguishes amylose from amylopectin?
Which type of amylase is found in saliva and pancreatic juice?
Which type of amylase is found in saliva and pancreatic juice?
What is a key characteristic of pure starch?
What is a key characteristic of pure starch?
Signup and view all the answers
How does starch serve as a storage material in plants?
How does starch serve as a storage material in plants?
Signup and view all the answers
Which of the following best describes the molecular structure of amylopectin?
Which of the following best describes the molecular structure of amylopectin?
Signup and view all the answers
Which of the following conditions could result from polysaccharide dysfunction?
Which of the following conditions could result from polysaccharide dysfunction?
Signup and view all the answers
What type of glucose does starch primarily consist of?
What type of glucose does starch primarily consist of?
Signup and view all the answers
What type of glycosidic bonds link D-glucoses in glycogen?
What type of glycosidic bonds link D-glucoses in glycogen?
Signup and view all the answers
Which characteristic differentiates inulin from starch?
Which characteristic differentiates inulin from starch?
Signup and view all the answers
What effect does dietary fiber have in relation to cholesterol?
What effect does dietary fiber have in relation to cholesterol?
Signup and view all the answers
What color change indicates the presence of starch when iodine is applied?
What color change indicates the presence of starch when iodine is applied?
Signup and view all the answers
What causes mucopolysaccharidoses?
What causes mucopolysaccharidoses?
Signup and view all the answers
Which of the following is a feature of glycosaminoglycans?
Which of the following is a feature of glycosaminoglycans?
Signup and view all the answers
Which dietary component is primarily associated with preventing constipation?
Which dietary component is primarily associated with preventing constipation?
Signup and view all the answers
What is the role of core proteins in proteoglycans?
What is the role of core proteins in proteoglycans?
Signup and view all the answers
Which of the following represents a common misconception about starch digestion?
Which of the following represents a common misconception about starch digestion?
Signup and view all the answers
Which statement about amylose and amylopectin is false?
Which statement about amylose and amylopectin is false?
Signup and view all the answers
What is a common mistake regarding the role of glycogen in humans?
What is a common mistake regarding the role of glycogen in humans?
Signup and view all the answers
Which of the following is incorrect in relation to the health effects of dietary fibers?
Which of the following is incorrect in relation to the health effects of dietary fibers?
Signup and view all the answers
Which process is mistakenly attributed to starch when considering its role in food?
Which process is mistakenly attributed to starch when considering its role in food?
Signup and view all the answers
Study Notes
Polysaccharides
- Polysaccharides are high molecular weight carbohydrates
- They are insoluble non-sugars
- They are composed of many monosaccharides
- On hydrolysis, they yield monosaccharides or related products
- They are polymeric anhydrides of simple sugars
- D-glucose is a common component
Types of Polysaccharides
-
Homopolysaccharides
- Yield a single monosaccharide on hydrolysis
- Examples: starch, glycogen, cellulose, inulin, chitin
-
Heteropolysaccharides
- Yield a mixture of monosaccharides on hydrolysis
- Examples: Hyaluronic acid, chondroitin sulfates, dermatan sulfate, heparin
Functions of Polysaccharides
-
Storage: Store energy (starch, glycogen, inulin)
- Starch is stored in plant cells and is a major source of energy
- Glycogen is stored in animal cells for energy needs
-
Structural: Provide structural support (cellulose, chitin)
- Cellulose is abundant in plants, forming cell walls.
- Chitin is found in the exoskeletons of insects and crustaceans, offering structural strength.
Other Constituents of Polysaccharides
- D- and L-galactose; D-mannose; D-xylose; L-arabinose
- D-glucuronic acid; D-galacturonic acid; D-mannuronic acids
- D-glucoseamine; D-galactoseamine; Aminouronic acids
Differences in Polysaccharides
- Molecular weight
- Chain nature (linear or branched)
- Glycosidic bond type (α or β)
- Linkage type (e.g., 1-2, 1-3, 1-4, etc.)
- Most carbohydrates of nature are polysaccharides
Chemical Classification of Polysaccharides
- HomoPolysaccharides: On hydrolysis, yield a single monosaccharide.
- HeteroPolysaccharides : On hydrolysis, yield a mixture of monosaccharides
Functional Aspects of Polysaccharides
- Nutrient/Digestible Polysaccharides: Act as metabolic reserve of monosaccharides in plants and animals; examples include starch, glycogen, and inulin.
- Structural/Indigestible Polysaccharides: Serve as rigid mechanical structures in plants and animals including cellulose, pectin, chitin, hyaluronic acid, chondroitin
Functions
- Provide energy source, stored as glycogen
- Help oxidize fat without carbohydrates
- Spare proteins for building/repairing tissues
- Aid digestion
- Help build cell and tissue structures
- Are a source of carbon for synthesizing other compounds
Homopolysaccharides
-
Starch: Polymer of α-glucose, stored as starch grains in chloroplasts and storage organs of plants like seeds.
- Consists of two molecules: amylose and amylopectin
- Amylose: linear, helical, soluble in water, gives blue color with iodine
- Amylopectin: branched, insoluble in water, gives a violet color with iodine.
-
Glycogen: Polymer of α-glucose, stored in animal livers and muscles, acting as a reserve energy source
- Highly branched
- Compact structure, readily releasing glucose units for energy needs
-
Cellulose: Linear polymer of β-glucose, composing plant cell walls
- Insoluble in water, providing structural strength
-
Inulin: Polymer of fructose, stored in plant tubers and roots.
- Lower molecular weight than starch, soluble in water.
Occurrence of Starch
- Grains, potatoes, beans, chestnuts
- It is usually compactly inside the plant cells
- Insoluble granule; spherical, lens-shaped, ovoid with layered structures
Hydrolysis of Starch
- Amylase enzymes (α-amylase in saliva/pancreatic juice; β-amylase in sprouted grains/malts) are involved in breaking down starch into maltose, and further to glucose.
Characteristics of Pure Starch
- White, tasteless, odorless powder
- Insoluble in cold water or alcohol
- Composed of amylose and amylopectin molecules
Amylose Structure
- Linear chain connected by α(1→4) glycosidic bond
Amylopectin Structure
- Branched chain with both α(1→4) and α(1→6) glycosidic linkages
- Branching after 8-10 residues
Amylase Types
- α-amylase: present in saliva and pancreatic juice
- β-amylase: present in sprouted grains and malts.
- Both hydrolyze only α-glycosidic linkages
Glycogen
- D-glucose chains linked by α-1,4 and α-1,6 bonds
- Branching after 8-10 residues
Inulin
- Polymer of fructose, β(1,2) linked fructofuranoses
- Linear structure, no branching
- Lower molecular weight than starch
- Colors yellow with iodine
- Contains fructose on hydrolysis
- Sources: onions, garlic, Jerusalem artichoke
- Used clinically for glomerular filtration rate (GFR) measurement, as a soluble dietary fiber, appetite suppressant, and as a low-glycemic index sweetener, and fat/cream substitute.
Cellulose
- Linear polymer of β-glucose, β(1,4) linked
- Insoluble in water
- Major structural component of plant cell walls
- Synthesized and degraded on Earth; major part of plant carbon.
- Not metabolized by humans; but important source of bulk.
Pectin
- Intercellular substance in young plants and abundant in fruits (guava, apples, pears)
- Component of middle lamella between cell walls
- Polysaccharide of α-D-galacturonic acid; some free carboxyl groups are partly/completely esterified with methyl alcohol and others with calcium/magnesium ions
- Forms jellies with sugar.
Chitin
- Abundant biopolymer after cellulose
- Found in fungi, crabs, lobsters, and insect exoskeletons
- Polymer of N-acetyl-β-D-glucosamine linked by β(1-4) bonds
- Excellent mechanical properties for insect exoskeletons.
Heteropolysaccharides
- Linear polymers consisting of disaccharides (aminosugars-acid sugars)
- One monosaccharide is typically N-acetylglucosamine or N-acetylgalactosamine
- Other monosaccharide is D-glucuronic or L-iduronic acid
Mucopolysaccharidoses (MPS)
- Genetic disorders affecting glycosaminoglycan metabolism
- Caused by lysosomal enzyme deficiencies, leading to excessive accumulation/excretion of glycosaminoglycans
- Result in skeletal abnormalities among other clinical manifestations.
Hyaluronic Acid
- Most abundant mucopolysaccharide
- Found in connective tissues, vitreous humor, synovial fluid
- Highly viscous; acts as a lubricant, biological lubricant
- Composed of D-glucuronic acid and N-acetyl-D-glucosamine, β(1→3) and β(1→4) linkages
Hyaluronidase
- "Spreading factor" in skin and connective tissues
- Depolymerizes hyaluronic acid; allowing foreign bodies (pigments, bacteria) to penetrate tissues
- Plays a role in fertilization, aiding sperm passage for ovum penetration
Chondroitin
- Component of cartilage and cell coats
- Parent substance for chondroitin sulfate A and C
- Polymer of β-D-glucuronido-1, 3-N-acetylglucosamine/galactosamine linked by β(1-4) bonds
Chondroitin Sulfates
- Widely distributed; major structural components of cartilage, tendons, and bones
- Often associated with collagen and other proteins
- Derivatives of chondroitin
- Sulfate group esterified at carbon 4 (chondroitin sulfate A) or carbon 6 (chondroitin sulfate C).
- Both have β(1-3) and β(1-4) linkages
Dermatan Sulfate
- Structurally similar to chondroitin sulfate A, but with L-iduronic acid instead of D-glucuronic acid
- Known by its conventional name, chondroitin sulfate B; but different from chondroitin sulfates A and C
- Contains α(1→3) and β(1→4) linkages
Heparin
- Related to sulfated mucopolysaccharides
- Found in liver, lung, arterial walls (wherever mast cells are)
- Possibly neutralizes biogenic amines (e.g., histamine)
- Anticoagulant; inhibits prothrombin–thrombin conversion
- Heteropolysaccharide with multiple sugars in repeating units
Proteoglycans
- Conjugated proteins with core protein covalently linked to glycosaminoglycans (GAGs)
- Important structural components in tissues.
Biological Importance of Polysaccharides
- Act as metabolic reserves (starch, glycogen)
- Form structural components in plants/animals (cellulose, chitin)
- Used in various applications (wood, paper, explosives, packing materials, and food)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers key concepts related to polysaccharides, including their structure, function, and roles in biological systems. Test your knowledge on amylose, amylopectin, and other polysaccharides, as well as their impact on health and nutrition.
