The Greek word myxa means slime. They are known as hagfish. The ugly fish is called slime eel. Their number of species is 70.
1. Their bodies are slender, elongated, with slippery glands and without paired fins.
2. They look like eel or bine fish.
3. The spinal cord consists of notochord and fibrous neural tube.
4. Their mouth is marginal and has 4 pairs of gills.
5. They have 5–15 pairs of florets.
6. Their nasal sacs open into the oral cavity.
7. The forebrain forms the brain. Cerebellum absent. There are 10 pairs of carotid nerves.
8. They are known as hagfish.
9. They feed on annelids, molluscs, crustaceans, arthropods or dead fish.
10. The digestive system does not contain a stomach and the intestinal spiral is absent.
11. They are all marine.
12. Their life cycle does not have a larval stage.
13. They are unisexual animals. They are excreted. Eggs are yolky and large.
[KEY WORDS TO REMEMBER CHARACTERISTICS: bine, mouth margin, larynx, larynx, nasal sac, hagfish]

Polysaccharide is formed from the Greek words poly meaning many and saccharin meaning sugar. Carbohydrates that break down or break down into many molecules (more than 10) of monosaccharides are called polysaccharides. Their common symbol is (C6H10O5)n. where 10 ≥ n ≤ 3000|

Properties of polysaccharides
(i) It is a complex sugar.
(ii) Its wet analysis yields numerous monosaccharide molecules.
(iii) It is a large molecule.
(iv) Its molecular weight is more than 10,000 daltons.
(v) It is not sweet in taste.
(vi) It is non-granular and insoluble in water.
(vii) It does not contain aldehyde and ketone groups.
(viii) It is an insoluble sugar.

1. Classification based on work
Polysaccharides are divided into three categories based on function.
(i) Stored polysaccharides: All the carbohydrates that are stored in the body as stored food are called stored polysaccharides. For example, starch, glycogen, inulin, dextin, paramylam, livan etc. Starch is the main stored food in plants and glycogen in animals. Dr. Siddiq Publications
(ii) Structural polysaccharides: Carbohydrates which form the cell walls of plants are called structural polysaccharides. For example, cellulose, hemicellulose, pectic acid, chitin, keratin sulfate etc. Cellulose is the main structural component of the cell wall.
(iii) Complex polysaccharides: Those polysaccharides which are composed of sugars and non-sugars are called complex polysaccharides. Such as mucopolysaccharide, agar, hyaluronic acid, chondroitin sulfate, heparin etc. Dr. Siddiq Publications
2. Structural classification
Polysaccharides are divided into two categories based on structure.
(i) Homopolysaccharides or Homoglycans: Carbohydrates that are composed of monosaccharides of the same type are called homopolysaccharides or homoglycans. For example, starch, cellulose, glycogen, inulin etc.
(ii) Heteropolysaccharides or Heteroglycans: Carbohydrates composed of two or more types of monosaccharides are called heteropolysaccharides or heteroglycans. Such as hemicellulose, mucopolysaccharide, pectin, chitin, agar etc.
3. Unit Based Classification: On the basis of structural unit polysaccharides are of several types-
(i) Glucosan: The polysaccharide formed from glucose is called glucosan.
(ii) Fructosan: The polysaccharide formed by fructose is called fructosan.
(iii) Galactasan: The polysaccharide formed by galactose is called galactasan.
(iv) Hexosan: A polysaccharide composed of six carbon monosaccharides is called hexosan.

On the basis of structural unit polysaccharides are of several types-
(i) Glucosan: The polysaccharide formed from glucose is called glucosan.
(ii) Fructosan: The polysaccharide formed by fructose is called fructosan.
(iii) Galactasan: The polysaccharide formed by galactose is called galactasan.
(iv) Hexosan: A polysaccharide composed of six carbon monosaccharides is called hexosan.

Polysaccharides are divided into two categories based on structure.
(i) Homopolysaccharides or Homoglycans: Carbohydrates that are composed of monosaccharides of the same type are called homopolysaccharides or homoglycans. For example, starch, cellulose, glycogen, inulin etc.
(ii) Heteropolysaccharides or Heteroglycans: Carbohydrates composed of two or more types of monosaccharides are called heteropolysaccharides or heteroglycans. Such as hemicellulose, mucopolysaccharide, pectin, chitin, agar etc.

Polysaccharides are divided into three categories based on function.
(i) Stored polysaccharides: All the carbohydrates that are stored in the body as stored food are called stored polysaccharides. For example, starch, glycogen, inulin, dextin, paramylam, livan etc. Starch is the main stored food in plants and glycogen in animals. Dr. Siddiq Publications
(ii) Structural polysaccharides: Carbohydrates which form the cell walls of plants are called structural polysaccharides. For example, cellulose, hemicellulose, pectic acid, chitin, keratin sulfate etc. Cellulose is the main structural component of the cell wall.
(iii) Complex polysaccharides: Those polysaccharides which are composed of sugars and non-sugars are called complex polysaccharides. Such as mucopolysaccharide, agar, hyaluronic acid, chondroitin sulfate, heparin etc. Dr. Siddiq Publications

(i) It is a complex sugar.
(ii) Its wet analysis yields numerous monosaccharide molecules.
(iii) It is a large molecule.
(iv) Its molecular weight is more than 10,000 daltons.
(v) It is not sweet in taste.
(vi) It is non-granular and insoluble in water.
(vii) It does not contain aldehyde and ketone groups.
(viii) It is an insoluble sugar.

Polysaccharide is formed from the Greek words poly meaning many and saccharin meaning sugar. Carbohydrates that break down or break down into many molecules (more than 10) of monosaccharides are called polysaccharides. Their common symbol is (C6H10O5)n. where 10 ≥ n ≤ 3000.

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

Properties of oligosaccharides
(i) Oligosaccharides are simple sugars.
(ii) It can be wet analyzed.
(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 is an insoluble sugar.

Some oligosaccharides
(i) Trisaccharides: Carbohydrates which break down or break down into three molecule monosaccharides are called trisaccharides. Such as – raffinose, rabinose, raminose and malizitose. Breaking down raffinose yields glucose, fructose and galactose. Dr. Siddiq Publications
(ii) Tetrasaccharides: Carbohydrates which break down or break down into four molecules of monosaccharides are called tetrasaccharides. Its chemical symbol is C24H42O21. Eg – Stachyose, Skardose etc. When stachyose is broken down, glucose, fructose and two molecules of galactose are obtained. Tetrasaccharides are found in plants of the Leguminosae and Labiatae families. Cucurbita pepo plant contains tetrasaccharides.
(iii) Pentasaccharides: Carbohydrates which break down or break down into monosaccharides of five molecules are called pentasaccharides. For example, verbose. The root of Verbescus thepus plant contains pentasaccharides.
(iv) Hexasaccharide: Carbohydrates composed of six monosaccharide molecules are called hexasaccharides. For example, α-Cyclodextrin.
(v) Heptasaccharides: Carbohydrates which are made up of seven molecules of monosaccharides are called heptasaccharides.
(vi) Octasaccharides: Carbohydrates which are composed of eight molecules of monosaccharides are called octasaccharides.
(vii) Nanasaccharides: Non-carbohydrate molecules composed of monosaccharides are called Nanasaccharides.
(viii) Decasaccharides: Carbohydrates which are composed of ten molecules of monosaccharides are called Decasaccharides.

(i) Trisaccharides: Carbohydrates which break down or break down into three molecule monosaccharides are called trisaccharides. Such as – raffinose, rabinose, raminose and malizitose. Breaking down raffinose yields glucose, fructose and galactose. Dr. Siddiq Publications
(ii) Tetrasaccharides: Carbohydrates which break down or break down into four molecules of monosaccharides are called tetrasaccharides. Its chemical symbol is C24H42O21. Eg – Stachyose, Skardose etc. When stachyose is broken down, glucose, fructose and two molecules of galactose are obtained. Tetrasaccharides are found in plants of the Leguminosae and Labiatae families. Cucurbita pepo plant contains tetrasaccharides.
(iii) Pentasaccharides: Carbohydrates which break down or break down into monosaccharides of five molecules are called pentasaccharides. For example, verbose. The root of Verbescus thepus plant contains pentasaccharides.
(iv) Hexasaccharide: Carbohydrates composed of six monosaccharide molecules are called hexasaccharides. For example, α-Cyclodextrin.
(v) Heptasaccharides: Carbohydrates which are made up of seven molecules of monosaccharides are called heptasaccharides.
(vi) Octasaccharides: Carbohydrates which are composed of eight molecules of monosaccharides are called octasaccharides.
(vii) Nanasaccharides: Non-carbohydrate molecules composed of monosaccharides are called Nanasaccharides.
(viii) Decasaccharides: Carbohydrates which are composed of ten molecules of monosaccharides are called Decasaccharides.

(i) Oligosaccharides are simple sugars.
(ii) It can be wet analyzed.
(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 is an insoluble sugar.