They are essential catalysts which are needed to catalyse biochemical reactions, e.g., maltase, lactase, amylase, invertase, etc.

The main structural feature of reducing sugars is the presence of an aldehyde group (-CO) such as in glucose, mannose, galactose , etc. . Or the α -ketol grouping (-CO-CH₂OH) as present in fructose.

Polysaccharides are those carbohydrates which give large number of monosaccharides on hydrolysis.

(i) Vitamin 'A'
(ii) Vitamin 'K'

Amylose is water soluble linear polymer of α -glucose. Amylopectin is water insoluble branched chain polymer of α -glucose.

Vitamin E

Lactose is a diassacharide. On hydrolysis, it gives two molecules of monosaccharides, i.e., one molecule of each of D-(+)-glucose and D-(+)-galactose.
\(\underset { Lactose }{ { C }_{ 12 }{ H }_{ 22 }{ O }_{ 11 } } +{ H }_{ 2 }O\overset { { \quad H }_{ 3 }{ O }^{ + } }{ \underset { { orLactose\quad } }{ \longrightarrow } } \underset { D-(+)-Glucose }{ { C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 } } +\underset { D-(+)-Galactose }{ { C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 } } \)

The six memberd cyclic structure og glucose is called pyranous structure.

(i) Those carbohydrates which have free aldehyde group and reduce Fehling's solution are called reducing sugars.
(ii) When tertiary and secondary structures of protein is ruptured by heating, change in pH or by adding electrolyte it is called denaturation of a proteins.
(iii) We take oxygen from atmosphere and release CO₂. Plants take CO₂ and H₂O from atmosphere to prepare their food in presence of sunlight and release O₂ and thus O₂ is replenished in our atmosphere. 

(a) Isoelectric point: It is the pH at which +ve and -ve charges on zwitter ion are equal, e.g., amino acid exists as zwitter ion at pH =5.5 to 6.3.
(b) Mutarotation : It is a spontaneous change in optical rotaion when an optically active substance is dissolved in water, e.g., \(\alpha\)-glucose, when dissolved  in water, its optical rotaion changes from 111^o to 52.5^o.
(c)Enzymes : They are biological catalysts which catalyse specific biochemical reactions, e.g., 
\(\underset { sucrose }{ C_{ 12 }H_{ 22 }O_{ 11 } } +H_{ 2 }O\quad \overset { invertase }{ \longrightarrow } \underset { Glucose }{ C_{ 6 }H_{ { 12 } }O_{ 6 } } +\underset { Fructose }{ C_{ 6 }H_{ 12 }O_{ 6 } } \)
Most of enzymes are globular proteins.

(i) Peptide linkage. Peptide bond is formed by the condensation of two or more same or different n-amino acids. The condensation occurs between amino acids with the elimination of water. In this case, the carboxyl group of one amino acid and amino group of another amino acid get condensed with the elimination of water molecule.
The resulting \(\quad O\\ \quad \parallel \\ -C-NH-\)  linkage is called peptide linkage. The formation of a dipeptide and the peptide 

(ii) Primary structure. The primary structure of proteins gives the sequence in which the amino acids are linked in one or more polypeptide chains of proteins. This is shown below:

(iii) Denaturation. A process that changes the physical and biological properties of proteins without affecting the chemical composition of a protein is called denaturation. The denaturation is caused by certain physical or chemical treatments such as changes in pH, temperature, presence of some salts or certain chemical agents.

Nucleic acids are biomolecules which are found in the nuclei of all living cells inform of nucleoproteins or chromosomes (proteins containing nucleic acids as the prosthetic group).
Nucleic acids are of two types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The two main functions of nucleic acids are:
(i) DNA is responsible for transmission of hereditary effects from one generation to another. This is due to the unique property of replication during cell division as a result of which two identical DNA strands are transferred to the daughter cells.
(ii) DNA and RNA are responsible for synthesis of all proteins needed for the growth and maintenance of our body. Actually, the proteins are synthesized by various RNA molecules (r-RNA, m-RNA and t-RNA) in the cell but the message for the synthesis of a particular protein is given by DNA molecules.

(i) Glycosidic linkage: The two monosaccharides units are joined together through an oxide linkage formed by loss of a molecule of H₂ O.
(ii) Invert sugar: Hydrolysis of sucrose brings about a change in a sign of rotation from dextro (+) to leavo (-) and the product is known as invert sugar.
(iii) Carbohydrates that yield two to ten monosaccharides units, on hydrolysis are called Polysaccharides. Examples are starch, cellulose, glycogen etc. 

(i) Vitamin B-complex and vitamin C are water soluble vitamins.
(ii) Vitamin C is chemically ascorbic acid while vitamin D is ergocalciferol.
(iii) Green leafy vegetables like spinach, cabbage, carrot etc.
(iv) It is essentially needed for body. The deficiency of vitamin K leads to blood clotting and even harmorrhage

(a) The penta-acetate of glucose does not react with hydroxylamine. It indicates that the carbonyl group of glucose is not free as it is present in cyclic form.
(b) Vitamin C is water soluble, that's why it cannot stored in our body.
(c) (i) Peptide linkage Proteins are connected to each other by –CO–NH– bond which is called the peptide linkage.
(ii) Denaturation When a native protein is subjected to physical change or chemical change, the hydrogen bonds are disturbed. As a result, globules unfold and helix gets uncoiled and protein loses its biological activity. This is known as denaturation of proteins.
Or
(c) (i) Anomers In carbohydrates, a pairs of anomers, is a near-identical stereoisomers that differ at only the anomeric carbon.
(ii) Glycosidic linkage The two monosaccharide units are joinied together through an oxide linkage, known as glycosidic linkage.