CBSE Class 11 Biology Chapter 11: Biomolecules NCERT Solutions

Solution: Macromolecules are large and complex biological molecules that are essential for life. They are typically formed by the joining of many smaller, repeating subunits called monomers through polymerization reactions. In biological systems, these large molecules often exist in a colloidal state within the intercellular fluid. Common examples of macromolecules include proteins (polymers of amino acids), polysaccharides (polymers of monosaccharides like glucose), and nucleic acids (polymers of nucleotides).

Solution:

Here are illustrations and explanations of the three types of bonds:

1. Glycosidic bond: This is a type of covalent bond that links two monosaccharide units together to form disaccharides, oligosaccharides, or polysaccharides. It is typically formed between the anomeric carbon (carbon 1) of one monosaccharide and a hydroxyl group (often on carbon 4) of another monosaccharide, with the release of a water molecule (dehydration synthesis). For example, in maltose, a glycosidic bond connects two glucose units between C1 of one and C4 of the other.

   $$C-O-C$$

   Glycosidic bond

2. Peptide bond: This is a covalent bond formed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another amino acid. This reaction also involves the release of a water molecule. The formation of a peptide bond links amino acids together to form polypeptides and proteins. The linkage is specifically an amide bond, represented as -CO-NH-.

   $$-CO-NH-$$

   Peptide bond

3. Phosphodiester bond: This is a strong covalent bond that links the 5' carbon of one deoxyribose or ribose sugar to the 3' carbon of the next deoxyribose or ribose sugar via a phosphate group. These bonds are crucial for forming the sugar-phosphate backbone of nucleic acids (DNA and RNA). Each phosphodiester bond involves a phosphate molecule esterified to two sugar molecules.

   $$Sugar-Phosphate-Sugar$$

   Phosphodiester bond

Solution: The tertiary structure of a protein 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 weak interactions and sometimes disulfide bridges between different parts of the polypeptide chain. These interactions can include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals forces. The tertiary structure is essential for the protein's specific biological function, as it determines the shape of active sites or binding surfaces.

Solution:

Here are 10 interesting small molecular weight biomolecules, along with information on their industrial production and buyers:

1. Glucose: A simple sugar, the primary source of energy for cells. Industry: Manufactured by hydrolysis of starch (e.g., corn starch). Buyers: Food and beverage industry, pharmaceutical industry (as an excipient and energy source), fermentation industries.
2. Fructose: A simple sugar found in fruits and honey. Industry: Often produced from glucose via isomerization. Buyers: Food and beverage industry (as a sweetener).
3. Amino Acids (e.g., L-Glutamic Acid): Building blocks of proteins. L-Glutamic acid is used as monosodium glutamate (MSG). Industry: Produced by fermentation. Buyers: Food industry (flavor enhancer), pharmaceutical industry, animal feed industry.
4. Nucleotides (e.g., Adenosine Triphosphate - ATP): Energy currency of the cell. Industry: Primarily synthesized biologically within cells; industrial production is complex and less common for bulk use, but research chemicals are available. Buyers: Research laboratories, pharmaceutical research.
5. Vitamins (e.g., Vitamin C - Ascorbic Acid): Essential organic compounds required in small quantities. Industry: Synthesized chemically or produced via fermentation. Buyers: Pharmaceutical industry (supplements), food industry (fortification), cosmetic industry.
6. Fatty Acids (e.g., Oleic Acid): Components of fats and oils. Industry: Isolated from natural fats and oils by hydrolysis. Buyers: Soap and detergent industry, cosmetic industry, food industry, chemical synthesis.
7. Cholesterol: A steroid lipid, important for cell membranes and hormone synthesis. Industry: Isolated from animal sources (e.g., wool grease, spinal cords). Buyers: Pharmaceutical industry (for steroid hormone synthesis), research laboratories.
8. Hormones (e.g., Insulin - though a protein, its precursors or analogs can be considered): Chemical messengers. Recombinant DNA technology is key for producing protein hormones like insulin. Industry: Primarily produced using recombinant DNA technology. Buyers: Pharmaceutical industry (for diabetes treatment).
9. Enzymes (e.g., Amylase): Biological catalysts. Industry: Produced by microbial fermentation. Buyers: Food industry (baking, brewing), detergent industry, textile industry, pharmaceutical industry.
10. Urea: A waste product of protein metabolism, also used industrially. Industry: Synthesized chemically from ammonia and carbon dioxide. Buyers: Fertilizer industry, chemical industry (resins), pharmaceutical industry.

Many industries, particularly the pharmaceutical, food, cosmetic, and chemical industries, rely on the isolation or synthesis of these small biomolecules. Buyers range from large corporations to research institutions, depending on the specific molecule and its application.