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Questions and Answers
What characteristic distinguishes glycoproteins from glycolipids?
What characteristic distinguishes glycoproteins from glycolipids?
Which statement about lipopolysaccharides is true?
Which statement about lipopolysaccharides is true?
What is a major consequence of bacterial endotoxins in humans?
What is a major consequence of bacterial endotoxins in humans?
Which polysaccharide is not digestible by the human body?
Which polysaccharide is not digestible by the human body?
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What role do gangliosides play in the cell membrane?
What role do gangliosides play in the cell membrane?
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What is the primary function of hyaluronic acid in the body?
What is the primary function of hyaluronic acid in the body?
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Which of the following is NOT a type of sulfated glucosaminoglycan?
Which of the following is NOT a type of sulfated glucosaminoglycan?
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What type of linkage connects the glucosaminoglycan to the protein core in proteoglycans?
What type of linkage connects the glucosaminoglycan to the protein core in proteoglycans?
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What causes mucopolysaccharidosis?
What causes mucopolysaccharidosis?
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Which glucosaminoglycan is primarily found in cartilage?
Which glucosaminoglycan is primarily found in cartilage?
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What is a characteristic of heparan sulfate compared to heparin?
What is a characteristic of heparan sulfate compared to heparin?
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What are the main components of proteoglycans?
What are the main components of proteoglycans?
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What role do glycosaminoglycans (GAGs) play in tissues?
What role do glycosaminoglycans (GAGs) play in tissues?
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Which disaccharide is composed of glucose and fructose?
Which disaccharide is composed of glucose and fructose?
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What is the primary characteristic of sucrose?
What is the primary characteristic of sucrose?
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Which polysaccharide is primarily the storage form of carbohydrates in plants?
Which polysaccharide is primarily the storage form of carbohydrates in plants?
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What type of glycosidic linkage is present in cellulose?
What type of glycosidic linkage is present in cellulose?
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What is one of the main functions of lactulose?
What is one of the main functions of lactulose?
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Which of the following is a characteristic of glycogen?
Which of the following is a characteristic of glycogen?
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Which type of polysaccharides are composed of different types of monosaccharides?
Which type of polysaccharides are composed of different types of monosaccharides?
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What is the main structural component of the cell wall in plants?
What is the main structural component of the cell wall in plants?
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Study Notes
Disaccharides
- Two monosaccharides linked by a glycosidic bond
- Hydrolyzed to form two simple sugars
Types of Disaccharides
-
Maltose: Glucose + Glucose
- Malt sugar
-
Lactose: Glucose + Galactose
- Main carbohydrate in milk
-
Sucrose: Glucose + Fructose
- Non-reducing sugar (no free carbonyl carbon)
-
Lactulose: β-galactose + fructose
- β-1-4 glycosidic bond between C1 of galactose and C4 of fructose
Importance of Lactulose
-
Laxative:
- Not absorbed by the intestine - creates bulk in the stool due to its osmotic effect
- Used to treat constipation
-
Liver Disease:
- Prevents bacterial production of ammonia in the intestines - beneficial for patients with liver disease who cannot deal with ammonia
Polysaccharides
- Large polymers of monosaccharides
- Two main types:
- Homopolysaccharides: Same type of monosaccharide
- Heteropolysaccharides: Different types of monosaccharides
Homopolysaccharides
-
Starch: Major storage form of carbohydrates in plants
- Two chains:
- Straight chain (amylose)
- Branched chain (amylopectin)
- Formed by repeated glucose units linked by α 1-4 glycosidic linkages and α 1-6 glycosidic linkages at branch points
- Two chains:
-
Glycogen: Major storage form of carbohydrates in animals
- Branched polymer of glucose
- Formed by repeated glucose units linked together by α 1-4 glycosidic linkages and α 1-6 glycosidic linkages at branch points
-
Cellulose: Forms the cell wall of plants
- Formed by repeated glucose units linked together by β 1-4 glycosidic linkages
- Not digested in the human body due to the lack of β-glycosidase enzyme
- Helps prevent constipation and forms the bulk of stool
Heteropolysaccharides (Complex Polysaccharides)
-
Nonsulfated Glucosaminoglycans
- Hyaluronic acid
-
Sulfated Glucosaminoglycans
- Heparin
- Heparan sulfate
- Keratan sulfate
- Chondroitin sulfate
- Dermatan sulfate
Hyaluronic Acid (Nonsulfated GAG)
- Composed of alternating residues of D-glucuronic acid and N-acetylglucosamine
- Clear, highly viscous solution
- Acts as a lubricant in synovial fluid of joints
- Forms the vitreous humor, which fills the eyeball
- Forms the extracellular matrix of cartilage and tendons
Defects in Hyaluronic Acid:
- Osteoarthritis
Heparin (Sulfated GAG)
- Anticoagulant
- Found in mast cells
- Repeated disaccharide units:
- Glucosamine-SO4 + Glucuronic acid ± Iduronic acid (variable)
Heparan Sulfate (Sulfated GAG)
- Similar structure to heparin, but more acetylated and less sulfated
Keratan Sulfate (Sulfated GAG)
- Found in two types:
- Type I: cornea
- Type II: cartilage
- Repeated disaccharide units:
- N-acetylglucosamine-SO4 + Galactose
Mucopolysaccharidosis
- Autosomal recessive disorder
- Caused by defects in lysosomal enzymes responsible for metabolism of membrane-associated glucosaminoglycans
- Leads to accumulation of glucosaminoglycans in lysosomes of affected cells
- Symptoms: skeletal deformities, mental retardation, and early death
Glycoconjugates
- Carbohydrates covalently bound to:
- Proteins (Proteoglycans & Glycoproteins)
- Lipids (Glycolipids & Lipopolysaccharides)
Proteoglycans
- Large macromolecules composed of glucosaminoglycan chains covalently bound to a membrane or secreted protein
- Glycan (CHO) constitutes the larger proportion
- GAGs are formed of amino sugars + uronic acids
- Major component of cartilage: confers strength and provides adhesion points, recognition signals, and information transfer between cells or between cells and the extracellular matrix
- Glucosaminoglycan attaches to the protein core via a trisaccharide linker composed of: Galactose, Galactose, Xylose, and Sulfur
- The protein core is coupled to the trisaccharide linker via its serine residue by an O-glycosidic bond
Glycoproteins
- Smaller oligosaccharide portion than proteins
- Present on cell surfaces (cell membranes) or extracellularly (plasma proteins, except albumin)
Glycolipids and Lipopolysaccharides
- Oligosaccharides are covalently bound to lipids
- Gangliosides are membrane lipids in eukaryotic cells complexed with oligosaccharides
- Some of these complexes determine blood groups
- Lipopolysaccharides are glycolipids present on the outer surface of bacterial cell walls of some Gram-negative bacteria
- Main target of antibodies produced by the immune system against these bacteria
- Lipopolysaccharides of some bacteria are toxic to humans and are called bacterial endotoxins
- Endotoxins cause:
- Decreased blood pressure
- Toxic shock, which accompanies infection with Gram-negative bacteria
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Description
Explore the fascinating world of disaccharides and polysaccharides in this quiz. Delve into the types of disaccharides such as maltose, lactose, and sucrose, and learn about their significance in nutrition and health. Understand the roles that these carbohydrates play in the body, particularly the importance of lactulose in treating constipation and liver disease.
