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Questions and Answers
What is a primary function of carbohydrates in the body?
What is a primary function of carbohydrates in the body?
Which of the following accurately classifies carbohydrates based on the type of carbonyl group?
Which of the following accurately classifies carbohydrates based on the type of carbonyl group?
What term describes carbohydrate polymers attached to proteins or lipids that play a signaling role?
What term describes carbohydrate polymers attached to proteins or lipids that play a signaling role?
In carbohydrate classification, which carbohydrate type consists of more than 10 monosaccharide units?
In carbohydrate classification, which carbohydrate type consists of more than 10 monosaccharide units?
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Which of the following is true about the suffix used for carbohydrates with a carbonyl group?
Which of the following is true about the suffix used for carbohydrates with a carbonyl group?
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What is a key characteristic that differentiates isomers from epimers?
What is a key characteristic that differentiates isomers from epimers?
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What are the products of cyclization of monosaccharides?
What are the products of cyclization of monosaccharides?
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Why are diastereomers important in biological processes?
Why are diastereomers important in biological processes?
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Which of the following statements about enantiomers is true?
Which of the following statements about enantiomers is true?
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What could be a potential consequence of using a drug that exists as diastereomers?
What could be a potential consequence of using a drug that exists as diastereomers?
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What is the characteristic of a sugar that allows it to act as a reducing agent?
What is the characteristic of a sugar that allows it to act as a reducing agent?
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Which of the following pairs represents important disaccharides?
Which of the following pairs represents important disaccharides?
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What type of bond is formed between monosaccharides?
What type of bond is formed between monosaccharides?
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What enzyme is responsible for catalyzing glycosidic bonds?
What enzyme is responsible for catalyzing glycosidic bonds?
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Which configuration is used to differentiate types of glycosidic bonds?
Which configuration is used to differentiate types of glycosidic bonds?
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What type of bond is formed when a sugar is attached to an –NH2 group?
What type of bond is formed when a sugar is attached to an –NH2 group?
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Which of the following describes lectins?
Which of the following describes lectins?
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What is the significance of oligosaccharides on cell surfaces?
What is the significance of oligosaccharides on cell surfaces?
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What are the three common disaccharides primarily composed of?
What are the three common disaccharides primarily composed of?
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Which of the following is TRUE about reducing sugars?
Which of the following is TRUE about reducing sugars?
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What is the functional impact of the 'sugar code'?
What is the functional impact of the 'sugar code'?
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How are isomers, epimers, and anomers classified?
How are isomers, epimers, and anomers classified?
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Which of the following best describes the role of selectins in the human body?
Which of the following best describes the role of selectins in the human body?
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Which of the following pairs of monosaccharides can produce more than one isoform?
Which of the following pairs of monosaccharides can produce more than one isoform?
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What type of bond holds carbohydrates together with non-carbohydrate molecules?
What type of bond holds carbohydrates together with non-carbohydrate molecules?
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Study Notes
Introduction to Carbohydrates
- Carbohydrates are the most abundant organic molecules in nature.
- They are also known as "hydrates of carbon".
- Their empirical formulas are (CH₂O)ₙ, where n ≥ 3.
Functions of Carbohydrates
- Provide dietary calories.
- Store energy in the body.
- Form components of cell membranes, involved in intercellular communication.
- Compose carbohydrate polymers – structural and protective elements in connective tissue (animals).
- Lubricate joints.
- Contribute to cell-cell recognition.
- Part of complex CHO polymers covalently attached to lipids or proteins (glycoconjugates). These polymers direct the intracellular destination or metabolic fate of hybrid molecules.
- Are structural components in organisms other than humans (e.g., cell walls of bacteria, exoskeletons of insects, fibrous cellulose of plants).
Classification by Number of Carbon Atoms
- Monosaccharides: one monomeric unit.
- Disaccharides: two monomeric units.
- Oligosaccharides: approximately 3-10 monosaccharides.
- Polysaccharides: more than 10 monosaccharides (can be hundreds).
- Glycoconjugates: linked to proteins or lipids.
Classification by Carbonyl Group
- Aldoses have an aldehyde group as their carbonyl group.
- Ketoses have a ketone group as their carbonyl group.
Isomers and Epimers
- Isomers have the same chemical formula but different structures.
- C₆H₁₂O₆: glucose, fructose, mannose, and galactose are examples.
- Epimers differ in the configuration around one carbon atom (other than the carbonyl carbon).
Monosaccharides
- Trioses (3 carbons): glyceraldehyde
- Tetroses (4 carbons): erythrose
- Pentoses (5 carbons): ribose, deoxyribose
- Hexoses (6 carbons): glucose, fructose
- Heptoses (7 carbons): sedoheptulose
- Nonoses (9 carbons): neuraminic acid
Important Disaccharides
- Sucrose
- Lactose
- Maltose
Monosaccharides to Polysaccharides
- Glycogen (branched) from animal sources.
- Starch from plants.
- Cellulose (unbranched) from plants.
- All are polymers of glucose linked by glycosidic bonds.
Glycosidic Bonds
- Bonds that join sugars together.
- Catalyzed by glycosyltransferases.
- Use nucleotide sugars (e.g., UDP-glucose) as substrates.
- Named according to the numbers of connected carbons and the position of the anomeric hydroxyl group. They are either α or β.
Complex Carbohydrates (Glycosides)
- Carbohydrates bonded to noncarbohydrates via glycosidic bonds.
- Examples include: purine and pyrimidine bases (nucleic acids), aromatic rings (steroids, bilirubin), proteins (glycoproteins, proteoglycans), and lipids (glycolipids).
N- and O-glycosides
- N-glycosides: the noncarbohydrate molecule has an -NH₂ group.
- O-glycosides: the noncarbohydrate molecule has an -OH group
The Sugar Code
- Monosaccharides form oligosaccharides (glycans).
- Glycans are dense and more informative than nucleic acids or proteins.
- Lectins (proteins) have highly specific carbohydrate-binding domains (glycan codes).
- Lectins initiate interactions between cells and govern the rate of peptide hormone and protein degradation; involved in cellular recognition and disease.
Thalidomide
- A drug used in the 1950s for morning sickness.
- Caused congenital deformities (phocomelia) in some babies.
- Exists as a mixture of optical isomers (R and S).
- R-form had sedative properties, S-form was teratogenic.
Reducing Sugars
- Sugars where the oxygen on the anomeric carbon is not attached to any other structure.
- Act as reducing agents.
- Examples: glucose, maltose, lactose.
Importance of Diastereomers
- Enzymes distinguish between different forms (e.g., α- and β-glucose) and preferentially work on one or the other.
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Description
This quiz covers the basics of carbohydrates, their functions in the body, and their classification based on the number of carbon atoms. Understand their importance in nutrition and cellular processes, as well as their various forms such as monosaccharides and disaccharides.
