The word oligosaccharide is formed from the Greek words oligo meaning few and saccharin meaning sugar. Oligosaccharide means few sugars. Carbohydrates that break down or break down into a few molecules of monosaccharides (3-10 molecules) are called oligosaccharides. Monosaccharides or monomers are linked by glycosidic bonds to form oligosaccharides. The attachment of the hydroxyl group of one monosaccharide to the hydroxyl group of another monosaccharide is called glycosidic linkage. Dr. Siddiq Publications

Carbohydrates that break down or break down into two molecules of monosaccharides are called disaccharides. Their chemical symbol is C12H22O11. A condensation reaction between two monosaccharide molecules results in the removal of one molecule of H2O from two –OH groups to form a disaccharide. Both monosaccharide molecules of the disaccharide form new C-O-C bonds. The C-O-C bond formed is called a glycosidic bond. Disaccharides such as sucrose (table sugar), maltose, isomaltose, lactose (milk sugar), cellobiose, trehalose etc. When sucrose or sugar is broken down, glucose and fructose are obtained. Again, lactose is broken down to glucose and galactose. Dr. Siddiq Publications

Monosaccharide is formed from the Greek word mono meaning one and saccharin meaning sugar. Monosaccharide means a single sugar. Carbohydrates that do not yield any other simple carbohydrate units when broken down or analyzed are called monosaccharides. Their common symbol is CnH2nOn. Monosaccharides have 3-10 carbons. Monosaccharides have a free aldehyde group (-CHO) at carbon 1 or a ketone group (>C=O) at carbon 2, so they are called reducing sugars or reducing sugars. Monosaccharides with aldehyde groups are called aldoses and monosaccharides with ketone groups are called ketoses. Aldehyde and ketone groups are reducing groups and sugars containing reducing groups are called reducing sugars.

Characteristics of monosaccharides
(i) It is a simple sugar.
(ii) It is photoactive.
(iii) It is a small molecule.
(iv) Its molecular weight is less than 10,000 daltons.
(v) It has a sweet taste.
(vi) It is granular and soluble in water.
(vii) It contains aldehyde and ketone groups.
(viii) It is called aldose or ketose sugar.
(ix) It is a repulsive sugar.

Classification of Monosaccharides
Monosaccharides can be divided into two groups based on the aldehyde or ketone group.
1. Aldose: Monosaccharides containing aldehyde groups are called aldoses. Such as glucose, erythrose, ribose, mannose etc. Dr. Siddiq Publications
2. Ketose: Monosaccharides containing ketone group are called ketose. Such as fructose, erythrulose, ribulose, dihydroxyacetone etc.

The different types of monosaccharides based on the number of carbons are-
1. Triose: Monosaccharides with three carbons are called triose. A triose with an aldehyde group is called an aldotriose and a ketone group with a ketotriose. Its molecular symbol is C3H6O3. For example, glyceraldehyde, dihydroxy acetone etc.
2. Tetrose: A four-membered monosaccharide is called a tetrose. Its molecular symbol is C4H8O4. A tetrose with a four-carbon aldehyde group is called an aldotetrose and a ketone group with a ketotetrose. Eg-Erythrose, Thirose, Erythrolose etc. Dr. Siddiq Publications
3. Pentose: Five carbon monosaccharides are called pentoses. Its molecular symbol is C5H10O5. Ribose and deoxyribose are pentose sugars and form nucleotides and nucleic acids. Examples – ribulose, xylulose, arabinose, lyxose, ribose, deoxyribose etc. Dr. Siddiq Publications
4. Hexose: Monosaccharides with six carbons are called hexoses. Its molecular symbol is C6H12O6. Hexoses of aldehyde groups are called aldohexoses and hexoses of ketone groups are called ketohexoses. They are known as blood sugar. There are 16 types of hexoses. The abundant hexose is the glucose that provides energy to living cells. Examples – glucose, fructose, galactose, mannose etc.
5. Heptose: A monosaccharide with seven carbons is called heptose. Its molecular symbol is C7H14O7. Its number is very less. It plays an important role in photosynthesis. Pseudoheptulose, monoheptulose etc.
6. Octose: An eight carbon monosaccharide is called octose. Its molecular symbol is C8H26O8. eg glucooctose. Dr. Siddiq Publications
7. Nenose: A monosaccharide having nine carbons is called nenose. Its molecular symbol is C9H18O9. eg gluconanose.
8. Decose: A ten carbon monosaccharide is called decose. Its molecular symbol is C10H30O10. E.g. Glucodecose.

1. Triose: Monosaccharides with three carbons are called triose. A triose with an aldehyde group is called an aldotriose and a ketone group with a ketotriose. Its molecular symbol is C3H6O3. For example, glyceraldehyde, dihydroxy acetone etc.
2. Tetrose: A four-membered monosaccharide is called a tetrose. Its molecular symbol is C4H8O4. A tetrose with a four-carbon aldehyde group is called an aldotetrose and a ketone group with a ketotetrose. Eg-Erythrose, Thirose, Erythrolose etc. Dr. Siddiq Publications
3. Pentose: Five carbon monosaccharides are called pentoses. Its molecular symbol is C5H10O5. Ribose and deoxyribose are pentose sugars and form nucleotides and nucleic acids. Examples – ribulose, xylulose, arabinose, lyxose, ribose, deoxyribose etc. Dr. Siddiq Publications
4. Hexose: Monosaccharides with six carbons are called hexoses. Its molecular symbol is C6H12O6. Hexoses of aldehyde groups are called aldohexoses and hexoses of ketone groups are called ketohexoses. They are known as blood sugar. There are 16 types of hexoses. The abundant hexose is the glucose that provides energy to living cells. Examples – glucose, fructose, galactose, mannose etc.
5. Heptose: A monosaccharide with seven carbons is called heptose. Its molecular symbol is C7H14O7. Its number is very less. It plays an important role in photosynthesis. Pseudoheptulose, monoheptulose etc.
6. Octose: An eight carbon monosaccharide is called octose. Its molecular symbol is C8H26O8. eg glucooctose. Dr. Siddiq Publications
7. Nenose: A monosaccharide having nine carbons is called nenose. Its molecular symbol is C9H18O9. eg gluconanose.
8. Decose: A ten carbon monosaccharide is called decose. Its molecular symbol is C10H30O10. E.g. Glucodecose.

Monosaccharides can be divided into two groups based on the aldehyde or ketone group.
1. Aldose: Monosaccharides containing aldehyde groups are called aldoses. Such as glucose, erythrose, ribose, mannose etc. Dr. Siddiq Publications
2. Ketose: Monosaccharides containing ketone group are called ketose. Such as fructose, erythrulose, ribulose, dihydroxyacetone etc.

Monosaccharides can be divided into two groups based on the aldehyde or ketone group.
1. Aldose: Monosaccharides containing aldehyde groups are called aldoses. Such as glucose, erythrose, ribose, mannose etc. Dr. Siddiq Publications
2. Ketose: Monosaccharides containing ketone group are called ketose. Such as fructose, erythrulose, ribulose, dihydroxyacetone etc.

(i) It is a simple sugar.
(ii) It is photoactive.
(iii) It is a small molecule.
(iv) Its molecular weight is less than 10,000 daltons.
(v) It has a sweet taste.
(vi) It is granular and soluble in water.
(vii) It contains aldehyde and ketone groups.
(viii) It is called aldose or ketose sugar.
(ix) It is a repulsive sugar.

Monosaccharide is formed from the Greek word mono meaning one and saccharin meaning sugar. Monosaccharide means a single sugar. Carbohydrates that do not yield any other simple carbohydrate units when broken down or analyzed are called monosaccharides. Their common symbol is CnH2nOn. Monosaccharides have 3-10 carbons. Monosaccharides have a free aldehyde group (-CHO) at carbon 1 or a ketone group (>C=O) at carbon 2, so they are called reducing sugars or reducing sugars. Monosaccharides with aldehyde groups are called aldoses and monosaccharides with ketone groups are called ketoses. Aldehyde and ketone groups are reducing groups and sugars containing reducing groups are called reducing sugars.

Carbohydrates are divided into two categories based on their oxidative capacity. These are-
(i) Reducing or reducing sugars: Those carbohydrates which have aldehyde and ketone radicals in free form and react with Fehling’s reagent, Benedict’s reagent and Burford’s reagent are called reducing or reducing carbohydrates. All monosaccharides are monosaccharides. Because the aldehyde group (-CHO) or ketone group (-CO) of monosaccharides are free. For example, glucose, fructose, galactose, glyceraldehyde, ribose, xylose etc.
(ii) Non-reducing or non-reducing sugars: Those carbohydrates which do not have aldehyde and ketone radicals in free form and do not react with Fehling’s reagent, Benedict’s reagent and Burford’s reagent are called non-reducing or non-reducing carbohydrates. Eg Sucrose, Starch, Cellulose, Glycogen, Trehalose etc. Dr. Siddiq Publications

Carbohydrates are divided into two categories based on taste. These are-
(i) Sugar: Carbohydrates that are sweet, granular and soluble in water are called sugars. Such as glucose, fructose, sucrose etc.
(ii) Non-sugar: Carbohydrates which are not sweet, granular and insoluble in water are called non-sugars. Such as starch, cellulose, glycogen etc.