Biomolecules Class 12 Notes - Chapter 14

Carbohydrates are classified into three groups viz monosaccharides, disaccharides, polysaccharides. Glucose is obtained by the digestion of starch. Polysaccharides and disaccharides are formed by the monosaccharides connected with glycosidic linkages between them. Proteins are a chain of twenty different α-amino acids which are linked by peptide bonds. Around ten amino acids cannot be synthesized by our body and must be consumed through diet. These are called essential amino acids. Certain dynamic and structural functions are carried out by protein. Proteins are classified as simple proteins, and secondary or tertiary. Simple proteins are the proteins containing only α-amino acids. Whenever there is a change in PH or temperature the secondary and tertiary proteins get disturbed and are unable to carry out their function. This is known as denaturation of the protein. Enzymes increase the rate of a chemical reaction and are very selective and specific in their action. Chemically every enzyme is a protein.

Types Of Nucleic Acids

Deficiency of vitamins leads to many diseases. Vitamins are food factors required for the body and are consumed through diet. They can be classified as fat-soluble and water-soluble. Polymers of nucleotides consisting of a phosphate moiety, base, and a pentose sugar are called nucleic acids. The transfer of characters from parents to offsprings is carried out y nucleic acids. Types of nucleic acids are RNA and DNA.

  • DNA – It contains a five-carbon sugar molecule which is called 2-deoxyribose, it has adenine, guanine, cytosine, and thymine, double-stranded structure, it has coded message for proteins to be synthesized.
  • RNA – It contains ribose. it has adenine, guanine, cytosine, and uracil, single-stranded structure, protein synthesis is carried out by three types of RNA viz mRNA, rRNA, and tRNA.

Few Important Questions

  1. How are starch and cellulose structurally different??
  2. What is Peptide linkage?
  3. Define nucleic acids. List their important functions.
  4. Mention the different types of RNA present in the cell?
  5. What are monosaccharides? What are disaccharides? Write the difference between them.

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Presence of gills in the tadpole of frog indicates that :