10 Questions
What is keratan?
A mucopolysaccharide
What is the main function of glycosaminoglycans (GAGs)?
To act as a lubricant and cushion for tissues
What is the property of glycosaminoglycans (GAGs) that allows them to hold large quantities of water?
Repulsion of their negative charges
What is the result of compressing a solution of glycosaminoglycans (GAGs)?
The water is squeezed out and the GAGs occupy a smaller volume
What happens to glycosaminoglycans (GAGs) when the compression is released?
They return to their original hydrated volume
What is the cause of resilience of synovial fluid and the vitreous humor of the eye?
The repulsion of their negative charges
What type of molecule is keratan composed of?
D-galactose and N-acetylglucosamine-6-sulfate
What is a characteristic of glycosaminoglycans (GAGs)?
They are structural components of connective tissue
What is true about keratan?
It is a minor constituent of proteoglycans
What is the function of glycosaminoglycans (GAGs) in connective tissue?
To provide structural support
Study Notes
Carbohydrates
- Carbohydrates are classified into simple and compound carbohydrates.
- Simple carbohydrates include monosaccharides, which are the building blocks of carbohydrates.
- Compound carbohydrates are formed by the condensation of two or more monosaccharides.
Monosaccharides Derivatives
- Sugar derivatives are formed by modifying monosaccharides through oxidation, reduction, or replacement of hydroxyl groups.
- Types of sugar derivatives include:
- Sugar acids (e.g. aldonic acids, uronic acids, aldonic acids)
- Sugar alcohols (e.g. sorbitol, mannitol)
- Amino sugars (e.g. replacement of hydroxyl group with an amino group)
- Deoxy sugars (e.g. replacement of hydroxyl group with a hydrogen atom)
Disaccharides
- Disaccharides are formed by the condensation of two monosaccharides.
- The general formula for disaccharides is Cn(H2O)n-1.
- Examples of disaccharides include:
- Maltose (2 α-glucose molecules linked by α1-4 glycosidic bond)
- Isomaltose (2 α-glucose molecules linked by α1-6 glycosidic bond)
- Cellobiose (2 β-glucose molecules linked by β1-4 glycosidic bond)
- Lactose (β-glucose + β-galactose linked by β1-4 glycosidic bond)
- Sucrose (α-glucose + β-fructose linked by α1-β2 glycosidic bond)
Polysaccharides
- Homopolysaccharides are composed of a single type of monosaccharide.
- Examples of homopolysaccharides include:
- Glycogen (animal starch, stored in liver and muscles)
- Cellulose (structural carbohydrate in plants, found in plant cell walls)
- Heteropolysaccharides are composed of two or more different types of monosaccharides.
- Examples of heteropolysaccharides include:
- Glycosaminoglycans (GAGs) or mucopolysaccharides
- Proteoglycans (chains of GAGs attached to a protein core)
- Glycoproteins (protein core with a short branched chain of carbohydrate)
Glycosaminoglycans (GAGs)
- GAGs are long, unbranched polysaccharides containing a repeating disaccharide unit.
- They are composed of modified sugars, including:
- N-acetylgalactosamine (GalNAc) or N-acetylglucosamine (GlcNAc)
- Uronic acid (e.g. glucuronate or iduronate)
- Sulphate groups
- Examples of GAGs include:
- Hyaluronic acid (found in synovial fluid, vitreous humor of eyes, and loose connective tissue)
- Chondroitin sulphate (found in cartilage and bone)
- Dermatan sulphate (found in sclera of eyes and important for overall shape of eyes)
- Heparin (found in cells and highly acidic, anticoagulant)
- Keratan sulphate (found in proteoglycans and lacks uronic acid)
- GAGs act as a lubricant and cushion in connective tissue, and have the ability to hold large quantities of water due to their negative charges.
This quiz assesses the understanding of carbohydrates, including their structure, classification, functions, and properties. It covers simple and compound carbohydrates, lipids, and amino acids.
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