Carbohydrates Note For Nurses Part I

Definition:

Carbohydrates are defined chemically as aldehyde or ketone
derivatives of the higher polyhydric alcohols, or compounds which yield
these derivatives on hydrolysis.

Classification

Carbohydrates are divided into four major groups monosaccharides,
disaccharides, oligosaccharides and polysaccharides.

1. Monosaccharides: (also called ‘simple’ sugars) are those which cannot be hydrolyzed further into simpler forms.

General Formula =C_nH_2nO_n

Subdivision of Monosaccharides

They can be subdivided further:

(a) Depending upon the number of carbon atoms they possess, as trioses, tetroses, pentoses, hexoses, etc.

(b) Depending upon whether aldehyde (– CHO) or ketone (– CO) groups are present as aldoses or ketoses.

Sr.No	General Formula	Name On The Base of Carbon Atoms	On the Base of Functional Group
			Aldehyde or Aldo Sugars	Ketone or Keto Sugars
01	C3H6O3	Trioses	Glyceraldehyde	Dihydroxyacetone
02	C4H8O4	Tetroses	Erythrose	Erythrulose
03	C5H10O5	Pentoses	Ribose	Ribulose
04	C6H12O6	Hexoses	Glucose	Fructose

2. Disaccharides:

Those sugars which yield two molecules of the same or
different molecules of monosaccharide on hydrolysis.

General Formula=C_n(H₂O)_n-1

Maltose yields 2 molecules of glucose on
hydrolysis.

Lactose yields one molecule of glucose and
one molecule of galactose on hydrolysis.

Sucrose yields one molecule of glucose and
one molecule of fructose on hydrolysis.

Lactulose a keto disaccharide

3. Oligosaccharides: Those sugars
which yield 3 to 10 monosaccharide units on hydrolysis, e.g. Maltotriose.

4. Polysaccharides (Glycans):
Those sugars which yield more than ten molecules of monosaccharides on
hydrolysis

General Formula= (C₆H₁₂O₆)_n

Polysaccharides are further divided into two groups:

a. Homo-polysaccharides (homoglycans):
Polymer of same monosaccharide units. Examples—Starch, glycogen, inulin,
cellulose, dextrins, dextrans.

b. Hetero-polysaccharides
(heteroglycans): Polymer of different monosaccharide units or their
derivatives. Example—Mucopolysaccharides (glycosaminoglycans).

Biomedical Importance of Carbohydrates

• Chief source of energy.

• Constituents of compound lipids and conjugated proteins. 

•
Degradation products act as “promoters” or ‘catalysts’.

• Certain carbohydrate derivatives are used as drugs like cardiac
glycosides/antibiotics.

• Lactose principal sugar of milk in lactating mammary gland.

• Degradation products utilized for synthesis of other substances
such as fatty acids, cholesterol, amino acid, etc.

• Constituents of mucopolysaccharides which form the ground
substance of mesenchymal tissues.

• Inherited deficiency of certain enzymes in metabolic pathways of
different carbohydrates can cause diseases, e.g. galactosemia, glycogen storage
diseases (GSDs), lactose intolerance, etc.

• Derangement of glucose metabolism is seen in diabetes mellitus.

Reference:

Notes Made By The Help of “The Text Book of Medical Biochemistry By MN. Chatterjea 8th Edition“