Questions and Answers
What is the general formula for carbohydrates?
Which of the following is NOT a monosaccharide?
Which monosaccharide is a component of RNA and DNA?
Which of the following is NOT a function of carbohydrates in the body?
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Which type of carbohydrate is considered the building block of all carbohydrates?
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Which of the following is a hexose sugar?
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Which of the following is a disaccharide?
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Which of the following statements is TRUE about monosaccharides?
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What type of monosaccharides contains an aldehyde group?
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Which of the following is the mother compound of aldoses?
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Which disaccharide is not considered reducing?
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What is the general structure of ketoses characterized by?
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Oligosaccharides are defined as polymers of how many monosaccharide units?
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Which enzyme hydrolyzes lactose into glucose and galactose?
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Which type of polysaccharides are built from more than 10 monosaccharide units?
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Which example represents a ketose?
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Study Notes
Carbohydrates
- Carbohydrates are the most abundant organic molecules in nature, formed of carbon, hydrogen, and oxygen atoms with a ratio of 1:2:1 and the general formula Cn(H2O)n.
- They are organic substances (polyhydroxy aldehyde or ketone) and most names for sugars end in -ose.
Biomedical Importance of Carbohydrates
- Carbohydrates are the chief source of energy for most organisms.
- They act as a storage form of energy in the body.
- They serve as cell membrane components that mediate some forms of intercellular communication.
- Ribose and deoxyribose sugars form part of the structure of RNA and DNA.
- Major antigens are carbohydrates in nature, e.g., blood group substances.
Classification of Carbohydrates
- Carbohydrates are classified according to the hydrolysis products (number of individual simple units) into:
- Monosaccharides: contain 1 sugar unit (cannot be hydrolyzed), e.g., Glucose, galactose, mannose, and fructose.
- Disaccharides: contain 2 sugar units, e.g., Maltose, lactose, and sucrose.
- Oligosaccharides: contain 3-10 sugar units.
- Polysaccharides: contain more than 10 sugar units, e.g., Starch, glycogen, and cellulose.
Monosaccharides
- Monosaccharides are the simplest units of carbohydrates and the building blocks.
- The general formula is (CH2O)n, so the name of carbohydrates (carbon + H2O).
- The ratio between carbon and H2O is 1.
- Most monosaccharides occurring in mammals are D sugars.
- Examples of monosaccharides include Glucose, mannose, galactose, and fructose.
Classification of Monosaccharides
- Classification based on the number of carbon atoms:
- Trioses: contain 3 carbon atoms.
- Tetroses: contain 4 carbon atoms.
- Pentose: contain 5 carbon atoms.
- Hexoses: contain 6 carbon atoms.
- Classification based on the functional group:
- Aldoses: monosaccharides containing an aldehyde group (-CH=O), e.g., Glyceraldehyde, erythrose, ribose, glucose, galactose, and mannose.
- Ketoses: monosaccharides containing a ketone group (-C=O), e.g., Dihydroxyacetone, erythrulose, ribulose, and fructose.
Disaccharides
- Disaccharides consist of two monosaccharides united together by glycosidic linkage.
- Disaccharides are classified into reducing disaccharides and non-reducing disaccharides.
- Examples of disaccharides include:
- Sucrose (non-reducing): hydrolyzed by sucrase enzyme into Glucose + Fructose.
- Lactose (reducing): hydrolyzed by lactase enzyme into Galactose + Glucose.
- Maltose (reducing): hydrolyzed by maltase enzyme into 2 Glucose.
Oligosaccharides and Polysaccharides
- Oligosaccharides are polymers of 3-10 monosaccharide units and are not an important source of carbohydrates in the diet for humans.
- Polysaccharides are composed of more than 10 monosaccharide units linked by glycosidic bonds and are non-reducing.
- Examples of polysaccharides include Starch, glycogen, and cellulose.
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Description
This quiz covers the chemistry of carbohydrates, including their structure, composition, and properties. It's based on Lecture 7 by Dr. Wael Sobhy Darwish, a Biochemistry PhD.
