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Questions and Answers
Which of the following statements accurately defines anomers?
Which of the following statements accurately defines anomers?
What is the key difference between epimers and anomers?
What is the key difference between epimers and anomers?
Which of the following pairs are correctly classified as epimers?
Which of the following pairs are correctly classified as epimers?
L-Ascorbic acid is an example of which type of compound?
L-Ascorbic acid is an example of which type of compound?
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What process leads to the formation of sugar acids?
What process leads to the formation of sugar acids?
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What characteristic defines the sugar mentioned in the content as a non-reducing sugar?
What characteristic defines the sugar mentioned in the content as a non-reducing sugar?
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Why is the sugar referred to as 'invert sugar' upon hydrolysis?
Why is the sugar referred to as 'invert sugar' upon hydrolysis?
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Which statement correctly describes trehalose?
Which statement correctly describes trehalose?
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What is the levorotatory power of fructose as mentioned in the content?
What is the levorotatory power of fructose as mentioned in the content?
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Which organisms are known to have trehalose as a significant sugar component?
Which organisms are known to have trehalose as a significant sugar component?
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What is the primary role of carbohydrates in living organisms?
What is the primary role of carbohydrates in living organisms?
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Which of the following is an aldohexose?
Which of the following is an aldohexose?
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Fructose is primarily found in which of the following sources?
Fructose is primarily found in which of the following sources?
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In diabetes mellitus, which carbohydrate appears in urine due to high blood levels?
In diabetes mellitus, which carbohydrate appears in urine due to high blood levels?
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Which carbohydrate can be synthesized in the mammary gland to form lactose?
Which carbohydrate can be synthesized in the mammary gland to form lactose?
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Which sugar is known as the reference sugar due to its asymmetric carbon atom?
Which sugar is known as the reference sugar due to its asymmetric carbon atom?
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What type of activity do substances containing an asymmetric carbon atom exhibit?
What type of activity do substances containing an asymmetric carbon atom exhibit?
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What major function does galactose serve when converted in the liver?
What major function does galactose serve when converted in the liver?
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What type of linkage connects β-galactose and β-glucose in lactose?
What type of linkage connects β-galactose and β-glucose in lactose?
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Which sugar is considered the least sweet and most suitable for baby feeding?
Which sugar is considered the least sweet and most suitable for baby feeding?
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What is a characteristic of lactose related to fermentation?
What is a characteristic of lactose related to fermentation?
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What type of sugar is sucrose classified as?
What type of sugar is sucrose classified as?
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What is the building unit of cellulose?
What is the building unit of cellulose?
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What effect does lactose have in relation to constipation in infants?
What effect does lactose have in relation to constipation in infants?
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What type of sugar is formed when the hydroxyl group at C2 is replaced by an amino group?
What type of sugar is formed when the hydroxyl group at C2 is replaced by an amino group?
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Which of the following is NOT a benefit of lactose for infants?
Which of the following is NOT a benefit of lactose for infants?
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Which of the following disaccharides contains only α-glucose units?
Which of the following disaccharides contains only α-glucose units?
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Which amino sugar is known to enter into the structure of heparin?
Which amino sugar is known to enter into the structure of heparin?
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How does sucrose primarily differ from lactose in terms of its sugar composition?
How does sucrose primarily differ from lactose in terms of its sugar composition?
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Which disaccharide is a non-reducing sugar?
Which disaccharide is a non-reducing sugar?
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What is the glycosidic bond type present in isomaltose?
What is the glycosidic bond type present in isomaltose?
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Sialic acid is formed from which two components?
Sialic acid is formed from which two components?
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Which of the following disaccharides is formed from β-glucose and β-galactose?
Which of the following disaccharides is formed from β-glucose and β-galactose?
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What characteristic property do all reducing disaccharides share?
What characteristic property do all reducing disaccharides share?
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Which of the following is NOT a sugar alcohol?
Which of the following is NOT a sugar alcohol?
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Ribitol is classified as which type of sugar?
Ribitol is classified as which type of sugar?
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Sorbitol is produced by the reduction of which of the following sugars?
Sorbitol is produced by the reduction of which of the following sugars?
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Which of the following is a triose sugar?
Which of the following is a triose sugar?
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Which of the following sugars is a pentose?
Which of the following sugars is a pentose?
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How many isomers of glucose exist?
How many isomers of glucose exist?
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The most important epimer of glucose is which sugar?
The most important epimer of glucose is which sugar?
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Which sugar is primarily found in milk?
Which sugar is primarily found in milk?
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Study Notes
Biochemistry of Carbohydrates
- Carbohydrates are substances containing carbon, hydrogen, and oxygen.
- They are aldehyde (CHO) or ketone (C=O) derivatives of polyhydric alcohols (with more than one OH group).
- Carbohydrates are the chief source of energy for the body.
- They are important structural components in animal and plant cells.
- They are a part of nucleic acids, nucleotides, coenzymes, hormones, receptors, and enzymes.
- Carbohydrates function as antigens, such as blood group substances.
- Carbohydrates have a 1:2:1 ratio of carbon, hydrogen, and oxygen (Cn(H₂O)n).
Definition of Carbohydrates
- Carbohydrates are organic compounds containing carbon, hydrogen, and oxygen atoms.
- They are essentially aldehydes or ketones with multiple hydroxyl groups.
- They can be broadly classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
Importance of Carbohydrates
- Carbohydrates are the primary source of energy in the body.
- They serve as structural components of animal and plant cells.
- They are essential parts of nucleic acids, nucleotides, and coenzymes.
- Carbohydrates form important antigens, like blood group determinants.
- They participate in hormone and enzyme structures.
Classification of Carbohydrates
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Monosaccharides: Simple sugars, containing one sugar unit. Cannot be hydrolyzed.
- Named by the number of carbon atoms (e.g., triose, pentose, hexose) and the functional group (aldose, ketose).
- Examples: glucose, fructose, galactose, ribose.
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Disaccharides: Two monosaccharide units linked together through glycosidic bonds.
- Can be hydrolyzed into monosaccharides.
- Examples: maltose, sucrose, lactose.
- Oligosaccharides: Short chains of 3-10 monosaccharide units linked together.
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Polysaccharides: Long chains of monosaccharides joined by glycosidic bonds (more than 10 units).
- Examples: starch, glycogen, cellulose.
Monosaccharides
- Definition: Simple sugars – the basic units of carbohydrates.
- General Formula: Cn(H₂O)n
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Naming:
- Named according to the functional group: aldoses (aldehyde group) and ketoses (ketone group).
- Classified based on the number of carbon atoms: trioses, tetroses, pentoses, hexoses.
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Examples: Trioses (glyceraldehyde, dihydroxyacetone), Tetroses (erythrose, threose), Pentoses (ribose, deoxyribose, xylose), and Hexoses (glucose, fructose, galactose, mannose).
- Specific functions of the individual pentoses and hexoses will be discussed later.
Classification of Monosaccharides
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Trioses: 3 carbon atoms.
-Aldotriose: Glyceraldehyde (glycerose)
- Ketotriose: Dihydroxyacetone.
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Tetroses: 4 carbon atoms.
- Aldotetrose: Erythrose
- Ketotetrose: Erythrulose
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Pentoses: 5 carbon atoms.
- Aldopentoses: Ribose, arabinose, xylose, and lyxose
- Ketopentoses: Ribulose and xylulose
- Ribose is crucial in the structure of RNA and DNA. Ribose is also found in ATP, GTP and coenzymes NAD, NADP, and FAD.
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Hexoses: 6 carbon atoms.
- Aldohexoses: Glucose, mannose, and galactose
- Ketohexose: Fructose
Importance (Functions) of Hexoses
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Glucose: The primary energy source in the body, also known as "grape sugar"
- Produces other carbohydrates, e.g., glycogen, galactose
- Formed by hydrolysis of starch, dextrins, glycogen, sucrose, maltose, and lactose.
- Found in urine in diabetes mellitus.
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Galactose: Converted to glucose in the liver.
- Part of lactose (milk sugar) synthesis.
- Component of glycoproteins, glycolipids, and mucopolysaccharides.
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Fructose: "Fruit sugar" or "semen sugar".
- Sweetest sugar, levorotatory (levulose).
- Part of inulin and sucrose hydrolysis.
- Converted to glucose in the liver.
- Mannose: Found in glycoproteins and linked to sialic acid.
Ring (cyclic) Structure of Sugars
- Cyclic structures of glucose and fructose result from the reaction between the carbonyl carbon and a hydroxyl group.
- Furanose: 4-membered ring structure
- Pyranose: 5-membered ring structure
Asymmetric Carbon Atom
- Asymmetric carbon atoms are carbons that have four different groups attached to them.
- Glyceraldehyde is the reference sugar due to its single asymmetric carbon atom.
- Substances containing asymmetric carbon atoms exhibit optical activity and optical isomerism.
Optical Activity
- The ability of a substance to rotate plane-polarized light.
- Dextrorotatory (+) rotates light to the right.
- Levorotatory (-) rotates light to the left.
Optical Isomerism
- Isomers that are mirror images of each other but not superimposable.
- D and L isomers are a type of optical isomerism.
- Key sugars in the body are D-forms.
Structural Isomerism
- Isomers with the same chemical formula but different structural arrangement of the atoms.
Stereoisomerism
- Types of stereoisomerism:
- D and L isomerism (enantiomers)
- Anomers,
- Epimers,
- Geometric isomers
Examples of stereoisomers (Anomers & Epimers):
- Anomers: alpha and beta forms of the same sugar.
- Epimers: Isomers that differ in the configuration around only one carbon atom. Examples: Glucose and Mannose are epimers at C-2, and Glucose and Galactose are epimers at C-4.
Sugar Derivatives
- Sugar acids: Oxidation of carbohydrates. Examples: gluconic, glucuronic, and glucaric (saccharic) acids. L-ascorbic acid (Vitamin C) is an important sugar acid.
- Sugar alcohols: Reduction of the carbonyl group. Examples include sorbitol, mannitol, ribitol, and dulcitol.
- Deoxy sugars: Loss of the oxygen from a hydroxyl group. Examples include deoxyribose and fucose.
- Amino sugars: Hydroxyl group replaced by an amino group. Examples: glucosamine, galactosamine, and mannosamine. Amino sugars are often found in glycoproteins.
Disaccharides
- Reducing disaccharides: Contain a free anomeric carbon. Example: Maltose, isomaltose, cellobiose, and lactose
- Non-reducing disaccharides: Both anomeric carbons are involved in the glycosidic linkage. Example: Sucrose and trehalose
Examples of Disaccharides and their properties
- Maltose: Two glucose units linked by an α(1→4) glycosidic bond. Reducing disaccharide, produced by starch digestion.
- Isomaltose: Two glucose units linked by an α(1→6) glycosidic bond. Reducing disaccharide
- Cellobiose: Two glucose units linked by a β(1→4) glycosidic bond. Reducing disaccharide, building block of cellulose.
- Lactose: Glucose and galactose linked by a β(1→4) glycosidic bond. Reducing disaccharide, milk sugar. High in pregnant/nursing females.
- Sucrose (Table sugar): Glucose and fructose linked by an α(1→2) glycosidic bond. Non-reducing disaccharide. Sucrose is the most abundant disaccharide.
- Trehalose: Two glucose units linked by an α(1→1) glycosidic bond. Non-reducing disaccharide.
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Description
Test your knowledge on carbohydrates with this quiz that covers definitions, classifications, and examples of various sugar types and their roles in living organisms. Explore important concepts like anomers, epimers, and the significance of sugars such as trehalose and fructose.
