CBSE Class 11 Biology Chapter 9: Biomolecules NCERT Solutions

Solution: Macromolecules are large and complex molecules that are essential components of living organisms. They are formed through the process of polymerization, where numerous small, low molecular weight molecules (micromolecules) link together to form a larger structure. These large molecules typically exist in a colloidal state within the intercellular fluid. Common examples of macromolecules found in biological systems include polysaccharides (like starch and cellulose), proteins (made from amino acid monomers), and nucleic acids (like DNA and RNA, made from nucleotide monomers).

Solution:

These bonds are crucial for forming larger biological molecules from their respective monomers:

1. Glycosidic bond: This bond is formed between two monosaccharide units, typically involving the carbon atom at position 1 of one sugar and the carbon atom at position 4 of the adjacent sugar. This linkage is characteristic of carbohydrates like disaccharides and polysaccharides. The formation involves the removal of a water molecule (dehydration synthesis).

   

2. Peptide bond: A peptide bond is a covalent bond that forms between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another amino acid. This linkage results in the formation of a dipeptide and the release of a water molecule. Peptide bonds are the fundamental linkages that create polypeptide chains, the building blocks of proteins.

   

3. Phosphodiester bond: This is a strong covalent bond that links the phosphate group to the 5' carbon of one sugar molecule and the 3' carbon of the next sugar molecule in a nucleic acid chain. These bonds are responsible for creating the sugar-phosphate backbone of DNA and RNA, providing structural integrity to the genetic material.

   

Solution: The tertiary structure of proteins refers to the overall three-dimensional shape that a single polypeptide chain folds into. After forming secondary structures like alpha-helices and beta-sheets, the polypeptide chain undergoes further complex coiling and folding. This intricate spatial arrangement is stabilized by various types of interactions and bonds between different parts of the polypeptide chain, including hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals forces, and sometimes disulfide bridges (covalent bonds between cysteine residues). The tertiary structure is crucial for the protein's specific biological function, as it determines the shape of active sites or binding surfaces.

Solution: This question requires research beyond the provided text. Here are examples of small molecular weight biomolecules and potential industrial contexts:

10 Interesting Small Molecular Weight Biomolecules and Their Industrial Context:

1. Glucose: A simple sugar (monosaccharide).
   • Industry: Food and beverage, pharmaceutical, chemical industries.
   • Manufacturing: Primarily manufactured by isolation from starch hydrolysis (e.g., corn starch).
   • Buyers: Food manufacturers (sweeteners, ingredients), pharmaceutical companies (excipients, IV fluids), chemical industries (fermentation feedstock).
2. Fructose: Another simple sugar (monosaccharide).
   • Industry: Food and beverage.
   • Manufacturing: Isolated from fruits or produced from glucose via enzymatic isomerization (High Fructose Corn Syrup).
   • Buyers: Beverage companies, confectioneries, processed food manufacturers.
3. Sucrose: A disaccharide (glucose + fructose).
   • Industry: Food and beverage.
   • Manufacturing: Isolated and purified from sugarcane or sugar beets.
   • Buyers: Households, food processing industries, bakeries.
4. Alanine: An amino acid.
   • Industry: Pharmaceutical, food, cosmetic industries.
   • Manufacturing: Synthesized chemically or produced via fermentation; can be isolated from protein hydrolysates.
   • Buyers: Pharmaceutical companies (supplements, drug synthesis), food industry (flavor enhancers), cosmetic formulators.
5. Glycine: The simplest amino acid.
   • Industry: Pharmaceutical, food, chemical industries.
   • Manufacturing: Chemical synthesis is common; also isolated.
   • Buyers: Pharmaceutical companies (drug synthesis), food industry (sweetener component), chemical manufacturers.
6. Citric Acid: An organic acid.
   • Industry: Food and beverage, pharmaceutical, cleaning products.
   • Manufacturing: Produced industrially by microbial fermentation (using *Aspergillus niger*).
   • Buyers: Food and drink companies (acidulant, preservative), pharmaceutical firms, detergent manufacturers.
7. Lactic Acid: An organic acid.
   • Industry: Food, pharmaceutical, cosmetic, bioplastic industries.
   • Manufacturing: Produced by bacterial fermentation of carbohydrates.
   • Buyers: Food industry (preservative, flavoring), cosmetic companies, manufacturers of polylactic acid (PLA).
8. Urea: A simple organic compound.
   • Industry: Fertilizer, pharmaceutical, chemical industries.
   • Manufacturing: Synthesized chemically from ammonia and carbon dioxide.
   • Buyers: Agricultural sector (fertilizer), pharmaceutical companies (skin creams), chemical manufacturers.
9. Cholesterol: A steroid lipid.
   • Industry: Pharmaceutical, research.
   • Manufacturing: Isolated from animal sources (e.g., wool grease, spinal cords), though synthetic routes exist.
   • Buyers: Pharmaceutical companies (for drug synthesis, e.g., steroid hormones), research institutions.
10. Adenosine Triphosphate (ATP): The primary energy currency of cells.
    • Industry: Primarily research and specialized biochemical applications.
    • Manufacturing: Typically produced via enzymatic synthesis or extracted from biological sources for research purposes; not a large-scale industrial product for general sale.
    • Buyers: Research laboratories, biotechnology companies for specific assays.

Note: The scale of isolation versus synthesis varies greatly depending on the molecule. Many small biomolecules are produced efficiently through chemical synthesis or microbial fermentation rather than direct isolation from natural sources due to cost and yield considerations.