Questions and Answers
Carbohydrates are composed of carbon, hydrogen and ______ in a specific proportion.
oxygen
The formula for carbohydrates is expressed as (CH2O)______.
n
Certain carbohydrates can contain other elements such as ______ and nitrogen.
sulphur
CHO are defined as polyhydroxy ______ and ketones.
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Carbohydrates are divided into simple sugars (Saccharides) and ______ or polysaccharides.
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Monosaccharides are those sugars which on hydrolysis yield no ______ sugars.
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The general formula for monosaccharides is ______.
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A chain form monosaccharide with a carbonyl group on an end carbon is referred to as an ______.
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Bioses contain two carbon atoms and are rarely found in nature. The only known compound is ______.
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Triose contains ______ carbon atoms and represents the simplest form of monosaccharide sugar found in nature.
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Tetrose contains ______ carbon atoms, e.g., erythrose.
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Pentose are very common in plants and are the product of hydrolysis of polysaccharides such as ______.
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Hexoses are monosaccharides containing ______ carbon atoms.
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Heptose contains ______ carbon atoms and plays a key role in photosynthesis of plants.
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Oligosaccharides consist of short chain monosaccharide units joined by characteristic linkages called ______ bonds.
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Disaccharides on hydrolysis yield ______ molecules of monosaccharide.
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Sucrose yields
plus
plus
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Maltose yields
glucose plus glucose.
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Lactose yields
plus Galactose.
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Raffinose yields Glucose plus Fructose plus
.
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Gentinose yields Glucose plus Glucose plus
.
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Tetrasaccharides can yield
molecules of monosaccharides on hydrolysis.
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Polysaccharides are formed by condensation and the elimination of
.
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Homopolysaccharides give only one type of
unit on hydrolysis.
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Study Notes
Overview of Carbohydrates
- Composed of carbon, hydrogen, and oxygen, typically in a ratio similar to water (CH₂O)n.
- Include polyhydroxy aldehydes and ketones, derived from the hydrolysis of more complex structures.
- Key in pharmacognosy, forming glycosides and secondary metabolites during plant photosynthesis.
Classification of Carbohydrates
- Divided into simple sugars (saccharides) and complex carbohydrates (polysaccharides).
- Simple sugars categorized as mono, di, tri, tetra, etc., based on carbon count.
Monosaccharides
- Simplest form of carbohydrates, with the formula CₙH₂ₙOₙ.
- Subdivided into:
- Bioses: 2 carbon atoms (e.g., glycoaldehyde, C₂H₄O₂).
- Trioses: 3 carbon atoms (e.g., glyceraldehyde).
- Tetroses: 4 carbon atoms (e.g., erythrose).
- Pentoses: 5 carbon atoms, common in plants (e.g., ribose, arabinose, xylose).
- Hexoses: 6 carbon atoms, abundant in plants; include aldoses (glucose, mannose, galactose) and ketoses (fructose).
- Heptoses: 7 carbon atoms, rare, involved in photosynthesis and glucose metabolism (e.g., glucoheptalose).
Oligosaccharides
- Composed of short chains of monosaccharides connected by glycosidic bonds.
- Naming convention ends in “--ose”; typically not existing freely.
Disaccharides
- Yield two monosaccharide molecules upon hydrolysis.
- Examples include:
- Sucrose: glucose + fructose.
- Maltose: glucose + glucose.
- Lactose: glucose + galactose.
Trisaccharides
- Composed of three monosaccharide units upon hydrolysis.
- Examples include:
- Raffinose: glucose + fructose + galactose (found in sugarcane).
- Gentianose: glucose + glucose + fructose (found in gentian root).
Tetrasaccharides
- Yield four monosaccharide units upon hydrolysis.
- Example: Stachyose (1 glucose, 2 galactose, and 1 fructose).
Polysaccharides
- Complex carbohydrates yielding an indefinite number of monosaccharides.
- Formed through condensation reactions, eliminating water.
- Examples include:
- Cellulose: composed of glucose units with β-1,4 glycosidic linkages.
- Starch: glucose linked by α-1,4 and α-1,6 bonds.
- Commonly insoluable in water and non-sweet; often form colloidal suspensions.
Classification of Polysaccharides
- Based on hydrolysis products:
- Homopolysaccharides: yield one type of monosaccharide (e.g., starch, cellulose, glycogen).
- Heteropolysaccharides: yield multiple types (e.g., hemicellulose, pectin).
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Description
Learn about the definition and molecular structure of carbohydrates, including their composition of carbon, hydrogen, and oxygen, and how they are expressed by the formula (CH2O)n.
