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Questions and Answers
What is the significance of prefixes tri-, tetr-, pent- in a monosaccharide?
What is characteristic of dihydroxyacetone?
What is the purpose of Fischer's projection and Haworth's formation?
What is the result of monosaccharides having asymmetric carbon atoms?
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What is the standard reference molecule used in carbohydrate chemistry?
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What is the reason for monosaccharides forming rings?
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Which monosaccharide is a structural isomer of glucose?
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What component leads to cataract if in excess due to enzyme deficiency?
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Which disaccharide is commonly known as 'table sugar'?
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Which monosaccharide is a major source of dairy products like milk?
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In which type of proteins are L-arabinose and L-fucose commonly found?
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Which type of bond is formed between two monosaccharides when joined together?
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What type of bond connects the glucose and fructose molecules in sucrose?
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What is the main function of oligosaccharides in the cell membrane?
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Which type of sugar is less sweet and less soluble, found in mammalian milk?
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What do blood group ABO substances represent on the surface of red blood cells?
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Which sugar is a 6-carbon L-sugar in the chain gal - nag – gal – fuc?
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How are polysaccharides characterized in terms of their size?
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What is the main component of chitin?
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Which polymer is recommended for the prevention and management of osteoarthritis?
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In which polysaccharide is an anticoagulant found that is used in preventing blood clotting after surgery?
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What is the second type of monosaccharide present in heparin?
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Which polysaccharide is used in artificial skin and is composed of glucuronic acid and N-acetylgalactosamine?
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What type of glycosidic bonds are present in chitin?
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What type of polysaccharides contain only α-glucose units?
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Which molecule is a mixture of amylose (20%) and amylopectin (80%)?
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How are glucose units linked in amylopectin?
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Which heteropolysaccharides are commonly called glycosaminoglycans or mucopolysaccharides?
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What is the primary function of glycogen?
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What is the difference between ribose and deoxyribose?
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Study Notes
Monosaccharides
- Prefixes tri-, tetr-, pent- indicate the number of carbon atoms in the monosaccharide
- Simplest monosaccharides are trioses: glyceraldehyde (aldotriose) and dihydroxyacetone (ketotriose)
- Most carbohydrates of interest in human biochemistry are aldohexoses or aldopentoses
- Monosaccharides can exist in linear and cyclic forms
- Cyclic form can be represented in Haworth's formation or chair conformation
- Linear form is not very stable, so pentoses and hexoses tend to form rings for improved stability
Classification of Isomerism
- Aldose-ketose isomerism
- D- and L- forms
- Enantiomers, diastereomers, epimers
- Pyranose and furanose ring structures
- α- and β- anomers (anomerism)
Monosaccharide Structure
- Monosaccharides possess stereogenic centers (asymmetric carbon atoms)
- All carbohydrates contain at least one asymmetrical (chiral) carbon, except for dihydroxyacetone
- Glyceraldehyde is the standard reference molecule, and its presence confers optical activity
- Hormones such as insulin and glucagon are related to diabetes mellitus
Important Monosaccharides
- Fructose (C6H12O6): fruit sugar, sweeter than glucose, and has a structural isomerism with glucose
- Galactose (C6H12O6): found in dairy products, a component of lactose and glycoproteins in brain and nerve tissue
- Galactosemia: excess galactose results in cataract due to enzyme deficiency
Disaccharides
- Formed via condensation/dehydration reactions
- A H2O molecule is removed (condensation) from a pair of monosaccharide molecules when joined together
- The bond formed between 2 monosaccharides is called a glycosidic bond (O-glycosidic bond)
- Disaccharides can be hydrolyzed to form monosaccharide sub-units (reverse reaction)
Examples of Disaccharides
- Sucrose: glucose + fructose, commonly called "table sugar"
- Maltose: glucose + glucose, used to make malted candy
- Lactose: glucose + galactose, found in cow's milk
Oligosaccharides
- Contain 3-10 monosaccharide molecules which are liberated on hydrolysis
- Functions include cell recognition and cell adhesion in the cell membrane
- Normally present as glycans: oligosaccharide chains are linked to lipids or to amino acid side chains in proteins, by N- or O-glycosidic bonds
- Blood groups ABO substances are oligosaccharides present in most cells of the body and in certain secretions
Polysaccharides
- Large molecules > 10 monosaccharide units
- Joined by O-glycosidic linkages in one continuous chain or the chain may be branched
- Examples: chitin, hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin
Examples of Polysaccharides
- Chitin: second most abundant polysaccharide in nature, found in crustaceans and insects, used as surgical thread that biodegrades as a wound heals
- Hyaluronic acid (hyaluronate): found in synovial fluid in joints, eye, and in connective tissues, provides lubrication and shock absorption
- Heparin: anticoagulant used in preventing blood clotting after surgery and in blood sample tubes
- Chondroitin 6-sulphate: found in connective tissues, tendons, and cartilage, used in artificial skin and recommended for the prevention and management of osteoarthritis
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Description
Test your knowledge on the structure and classification of monosaccharides, including the prefixes indicating the number of carbon atoms and the different types of trioses. Explore the unique characteristics of monosaccharides, from aldohexoses to aldopentoses, and understand their biochemical importance.
