Carbohydrates: Definition and Molecular Composition
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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.

<p>aldehydes</p> Signup and view all the answers

Carbohydrates are divided into simple sugars (Saccharides) and ______ or polysaccharides.

<p>complex</p> Signup and view all the answers

Monosaccharides are those sugars which on hydrolysis yield no ______ sugars.

<p>lower</p> Signup and view all the answers

The general formula for monosaccharides is ______.

<p>CnH2nOn</p> Signup and view all the answers

A chain form monosaccharide with a carbonyl group on an end carbon is referred to as an ______.

<p>aldose</p> Signup and view all the answers

Bioses contain two carbon atoms and are rarely found in nature. The only known compound is ______.

<p>glycoaldehyde</p> Signup and view all the answers

Triose contains ______ carbon atoms and represents the simplest form of monosaccharide sugar found in nature.

<p>3</p> Signup and view all the answers

Tetrose contains ______ carbon atoms, e.g., erythrose.

<p>4</p> Signup and view all the answers

Pentose are very common in plants and are the product of hydrolysis of polysaccharides such as ______.

<p>hemicellulose</p> Signup and view all the answers

Hexoses are monosaccharides containing ______ carbon atoms.

<p>6</p> Signup and view all the answers

Heptose contains ______ carbon atoms and plays a key role in photosynthesis of plants.

<p>7</p> Signup and view all the answers

Oligosaccharides consist of short chain monosaccharide units joined by characteristic linkages called ______ bonds.

<p>glycoside</p> Signup and view all the answers

Disaccharides on hydrolysis yield ______ molecules of monosaccharide.

<p>two</p> Signup and view all the answers

Sucrose yields

plus

plus

<p>Glucose, Fructose</p> Signup and view all the answers

Maltose yields

glucose plus glucose.

<p>2</p> Signup and view all the answers

Lactose yields

plus Galactose.

<p>Glucose</p> Signup and view all the answers

Raffinose yields Glucose plus Fructose plus

.

<p>Galactose</p> Signup and view all the answers

Gentinose yields Glucose plus Glucose plus

.

<p>Fructose</p> Signup and view all the answers

Tetrasaccharides can yield

molecules of monosaccharides on hydrolysis.

<p>four</p> Signup and view all the answers

Polysaccharides are formed by condensation and the elimination of

.

<p>water</p> Signup and view all the answers

Homopolysaccharides give only one type of

unit on hydrolysis.

<p>monosaccharide</p> Signup and view all the answers

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.

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