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Questions and Answers
What percentage of human food do carbohydrates represent?
What percentage of human food do carbohydrates represent?
Which of the following is a major function of carbohydrates?
Which of the following is a major function of carbohydrates?
What is the general name ending for carbohydrates?
What is the general name ending for carbohydrates?
-ose
All monosaccharides are reducing sugars.
All monosaccharides are reducing sugars.
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_______ have the C=O group in carbon 1 and are aldoses.
_______ have the C=O group in carbon 1 and are aldoses.
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Haworth projection formulas are:
Haworth projection formulas are:
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Which of the following monosaccharides is a ketose?
Which of the following monosaccharides is a ketose?
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A hemiacetal is a cyclic structure of a ketose
A hemiacetal is a cyclic structure of a ketose
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In the open-chain form of a sugar, which carbon becomes the anomeric carbon in the cyclic form?
In the open-chain form of a sugar, which carbon becomes the anomeric carbon in the cyclic form?
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A furanose is a sugar that contains a five-membered ring as part of its cyclic structure
A furanose is a sugar that contains a five-membered ring as part of its cyclic structure
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The alpha and beta forms of the same sugar are called:
The alpha and beta forms of the same sugar are called:
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Glycosidic linkages between monosaccharide units may vary based on:
Glycosidic linkages between monosaccharide units may vary based on:
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Linear polymers are more water-soluble than branched ones
Linear polymers are more water-soluble than branched ones
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Branched polymers have one non-reducing end, and many reducing ends
Branched polymers have one non-reducing end, and many reducing ends
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Study Notes
Carbohydrates
- Represent 50-60% of human food and are the most abundant biomolecules on Earth
- Functions:
- Rapid source of energy
- Energy storage
- Structural components in cells and biomolecules
- Cell surface recognition
Classification of Carbohydrates
- Divided into four major groups:
- Monosaccharides (simple sugars)
- Disaccharides (two sugars)
- Oligosaccharides (a few sugars)
- Polysaccharides (many sugars)
Monosaccharides
- Also known as simple sugars
- Have at least 3 carbons
- General formula: (CH2O)n
- Have a carbonyl group (C=O) and hydroxyl groups (-OH)
- Classified into:
- Aldoses (C=O at carbon 1)
- Ketoses (C=O at other carbons)
- Differ in the number of carbons and hydroxyl groups
- Can exist as anomers (isomers that differ in the configuration of one carbon)
Disaccharides
- Formed by linking two monosaccharides through a glycosidic bond
- Can have different glycosidic bonds
- Examples:
- Lactose (milk sugar)
- Sucrose (table sugar)
Polysaccharides
- Long polymer chains of monosaccharides
- Used for energy storage or structure
- Can be linear or branched
- Examples:
- Starch (energy storage in plants)
- Glycogen (energy storage in animals)
- Cellulose (structural component in plants)
- Chitin (structural component in insects and crustaceans)
Glycoconjugates
-
Carbohydrates covalently linked to proteins or lipids
-
Examples:
- Proteoglycans (core protein with covalently attached glycosaminoglycans)
- Glycoproteins (carbohydrate-protein conjugates with branched oligosaccharides)
- Glycosphingolipids (sphingolipids with covalently bound oligosaccharides)### Carbohydrate Structures and Functions
-
Starch and glycogen form helical structures with intrachain hydrogen bonding
-
Cellulose and chitin form long, straight strands that interact with neighbouring strands
Glycoconjugates
- Glycoconjugates have oligo- or polysaccharides covalently attached to a protein or lipid
- Exposed on the outside of the plasma membrane
- Involved in signalling, transport within cells, recognition, and information transfer between cells and the extracellular matrix or parasites
Monosaccharides and Anomers
- Haworth projection formulas represent the cyclic form of sugars and show the distinction between alpha and beta anomers
- Fructose is a ketose
- A hemiacetal is a cyclic structure of a ketose
- In the open-chain form of a sugar, the highest numbered chiral centre becomes the anomeric carbon in the cyclic form
Glycosidic Linkages and Polymers
- Glycosidic linkages between monosaccharide units vary based on the anomeric form and the -OH group involved
- Linear polymers are more water-soluble than branched ones
- Branched polymers have one non-reducing end and many reducing ends
- Amylopectin and glycogen have a high degree of alpha(1-6) branching linkages
Glycoproteins and Biological Roles
- Glycoproteins are proteins covalently bound to sugars
- Carbohydrates play various roles in biology, including cell-cell communication, energy storage, and structural elements in cell walls
Specific Carbohydrates and Their Roles
- Cellulose: most abundant organic substance on earth, structural element in plant cell walls
- Chitin: exoskeleton structure in insects
- Glycogen: energy storage in animals, extensively branched
- Starch: energy storage in plants, less branched than glycogen
- Sucrose: not the most abundant organic substance on earth
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Description
This quiz covers the structure and types of glycosidic bonds in disaccharides, including lactose, and their reducing and non-reducing ends.
