Podcast
Questions and Answers
What is one major role of N-linked oligosaccharides in proteins?
What is one major role of N-linked oligosaccharides in proteins?
Why are most animals unable to digest cellulose?
Why are most animals unable to digest cellulose?
Which animals are known to efficiently digest cellulose?
Which animals are known to efficiently digest cellulose?
What effect does glycosylation have on the properties of proteins?
What effect does glycosylation have on the properties of proteins?
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What does the enzyme cellulase do?
What does the enzyme cellulase do?
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What defines a disaccharide?
What defines a disaccharide?
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Which of the following disaccharides is not a reducing sugar?
Which of the following disaccharides is not a reducing sugar?
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What type of polysaccharide contains only one kind of monosaccharide unit?
What type of polysaccharide contains only one kind of monosaccharide unit?
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Which of the following statements about glycosidic bonds is true?
Which of the following statements about glycosidic bonds is true?
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What is unique about N-linked glycoproteins?
What is unique about N-linked glycoproteins?
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Which carbohydrate residue is commonly linked to proteins in O-linked saccharides?
Which carbohydrate residue is commonly linked to proteins in O-linked saccharides?
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What distinguishes a heteropolysaccharide from a homopolysaccharide?
What distinguishes a heteropolysaccharide from a homopolysaccharide?
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What are the simplest oligosaccharides?
What are the simplest oligosaccharides?
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What role do N-linked oligosaccharides play in protein stability?
What role do N-linked oligosaccharides play in protein stability?
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Which enzyme is explicitly missing in most animals that prevents them from digesting cellulose?
Which enzyme is explicitly missing in most animals that prevents them from digesting cellulose?
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What effect does glycosylation have on the electrical charge of proteins?
What effect does glycosylation have on the electrical charge of proteins?
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Why can ruminant animals digest cellulose effectively?
Why can ruminant animals digest cellulose effectively?
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What happens to glucose derived from cellulose in ruminant animals?
What happens to glucose derived from cellulose in ruminant animals?
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What is the role of dehydration synthesis in the formation of glycosides?
What is the role of dehydration synthesis in the formation of glycosides?
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Which statement correctly describes sucrose in relation to reducing sugars?
Which statement correctly describes sucrose in relation to reducing sugars?
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What are glycosidic bonds primarily formed from?
What are glycosidic bonds primarily formed from?
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What defines homopolysaccharides?
What defines homopolysaccharides?
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Which type of polysaccharide can also be referred to as glycans?
Which type of polysaccharide can also be referred to as glycans?
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What distinguishes N-linked glycoproteins from O-linked glycoproteins?
What distinguishes N-linked glycoproteins from O-linked glycoproteins?
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Which of the following describes an aspect of polysaccharide structure?
Which of the following describes an aspect of polysaccharide structure?
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What makes a disaccharide a reducing sugar, as opposed to one that is not?
What makes a disaccharide a reducing sugar, as opposed to one that is not?
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Study Notes
Monosaccharides and their Reactions
- Monosaccharides are the simplest carbohydrates
- They are used to form disaccharides (e.g., maltose, sucrose, lactose) and polysaccharides via glycosidic bonds
- Pyranose and furanose forms react with alcohols in dehydration synthesis to form glycosides, retaining the α or β configuration at C-1
- The reaction results in a glycosidic bond via a condensation reaction and breaks by hydrolysis. The new bond is between an anomeric carbon and the oxygen of an alcohol.
Disaccharides
- Disaccharides are oligosaccharides composed of two monosaccharide units linked by a glycosidic bond
- Common examples include sucrose, maltose, and lactose
- These are mixed acetals, with one intramolecular hydroxyl group and one from another monosaccharide
- All except sucrose have a free anomeric carbon, making them reducing sugars
- Sucrose is a non-reducing sugar due to no free anomeric carbon
Polysaccharides
- Polysaccharides, also called glycans, are polymers of monosaccharides
- Homopolysaccharides consist of only one type of monosaccharide
- Heteropolysaccharides contain more than one type of monosaccharide
Glycosylation of Proteins
- Proteins can be glycosylated, which involves the addition of carbohydrates (oligosaccharides)
- O-linked glycosylation involves attaching carbohydrate residues (e.g., N-acetylgalactosamine, mannose, galactose, xylose) to the oxygen of hydroxyl groups on the protein.
- N-linked glycosylation involves attaching carbohydrate residues to the amide nitrogen of an asparagine residue. The core structure always contains two N-acetylglucosamine residues linked to a branched mannose triad
- N-linked glycoproteins can be high mannose, complex, or hybrid
- O-linked oligosaccharides are often found in cell surface glycoproteins and mucins
- N-linked oligosaccharides are found in various proteins, impacting their properties and functions, affecting solubility, mass and electrical charge
- Glycosylation can stabilize protein conformations and protect from proteolysis
Cellulose Digestion
- Cellulose is resistant to hydrolysis by acids and digestive enzymes because humans lack the enzyme cellulase, which breaks down β(1→4) linkages
- Ruminant animals can digest cellulose due to cellulase-secreting bacteria in their rumen. These bacteria produce β-glucosidase which hydrolyzes the cellulose.
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Description
This quiz covers the basics of carbohydrates, including monosaccharides, disaccharides, and polysaccharides. It explores their structures, formation, and unique properties. Test your knowledge on glycosidic bonds and the characteristics of these essential biomolecules.
