Biomolecules
Short Questions
1. What are biomolecules?
Answer: Biomolecules are organic molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.
2. What is the general formula of carbohydrates?
Answer: The general formula of carbohydrates is Cx(H2O)y, with a hydrogen-to-oxygen ratio of 2:1.
3. Name a monosaccharide found in DNA.
Answer: Deoxyribose is a monosaccharide found in DNA.
4. What is a glycosidic bond?
Answer: A glycosidic bond links monosaccharides in disaccharides and polysaccharides.
5. What is the main function of cellulose?
Answer: Cellulose provides structural support in plant cell walls.
6. What distinguishes saturated fatty acids?
Answer: Saturated fatty acids have no double bonds between carbon atoms.
7. Name a conjugated protein.
Answer: Haemoglobin is a conjugated protein with a haem prosthetic group.
8. What is the primary structure of a protein?
Answer: The primary structure is the linear sequence of amino acids in a polypeptide chain.
9. What sugar is present in RNA?
Answer: Ribose sugar is present in RNA.
10. What is the role of mRNA?
Answer: mRNA carries genetic information for protein synthesis.
11. What is an enzyme’s active site?
Answer: The active site is the region where the substrate binds to the enzyme.
12. What is the optimum temperature for most enzymes?
Answer: The optimum temperature for most enzymes is between 20–35°C.
13. What is metabolism?
Answer: Metabolism is the sum of all chemical reactions in a living organism.
14. What is a secondary metabolite?
Answer: Secondary metabolites are non-essential organic molecules produced by organisms.
15. Name a reagent used to test reducing sugars.
Answer: Benedict’s reagent is used to test reducing sugars.
Long Questions
1. Explain the classification of carbohydrates with examples.
Answer: Carbohydrates are classified into monosaccharides, disaccharides, and polysaccharides based on the number of sugar units. Monosaccharides (e.g., glucose, fructose) are simple sugars, disaccharides (e.g., sucrose, lactose) consist of two monosaccharides, and polysaccharides (e.g., starch, cellulose) are polymers of monosaccharides. These classes serve as energy sources, structural components, and storage molecules in living organisms.
2. Describe the biological significance of carbohydrates.
Answer: Carbohydrates are vital for energy production, with glucose serving as the main substrate for ATP synthesis. They also form structural components, such as cellulose in plant cell walls, and act as storage molecules like starch in plants and glycogen in animals. Additionally, lactose in milk provides energy for lactating infants.
3. Differentiate between saturated and unsaturated fatty acids with examples.
Answer: Saturated fatty acids lack double bonds between carbon atoms, making them solid at room temperature, e.g., palmitic acid. Unsaturated fatty acids have one or more double bonds, typically liquid, e.g., oleic acid. This structural difference affects their physical properties and biological roles, such as energy storage and membrane fluidity.
4. What are phospholipids, and what is their role in cell membranes?
Answer: Phospholipids consist of glycerol, two fatty acids, and a phosphate group, forming a hydrophilic head and hydrophobic tails. They arrange into a lipid bilayer in cell membranes, with heads facing water and tails inward, regulating the passage of substances. This structure ensures membrane integrity and selective permeability.
5. Explain the secondary structure of proteins with examples.
Answer: The secondary structure of proteins involves the folding of polypeptide chains into alpha-helices or beta-pleated sheets, stabilized by hydrogen bonds. Examples include keratin (alpha-helix) in hair and silk fibroin (beta-sheet) in silk fibers. These structures contribute to the protein’s stability and function.
6. Describe the structure of DNA as proposed by Watson and Crick.
Answer: Watson and Crick proposed that DNA is a double helix with two antiparallel polynucleotide strands linked by hydrogen bonds (A-T, G-C). The sugar-phosphate backbone forms the exterior, with bases paired inside, one turn measuring 34 Å. This structure enables DNA to store and replicate genetic information accurately.
7. What are the types of RNA, and what are their roles?
Answer: RNA types include mRNA, rRNA, and tRNA. mRNA carries genetic code for protein synthesis, rRNA forms the structural component of ribosomes, and tRNA transfers amino acids to ribosomes during translation. Each type is crucial for gene expression and protein production.
8. Explain the induced fit model of enzyme action.
Answer: The induced fit model, proposed by Koshland (1959), states that an enzyme’s active site reshapes to fit the substrate upon binding, enhancing catalysis. Unlike the rigid lock-and-key model, it highlights the enzyme’s flexibility, allowing precise substrate interaction. This model explains the high specificity and efficiency of enzymes.
9. What is the concept of the metabolic pool in cells?
Answer: The metabolic pool is a reservoir of biomolecules in a cell, acted upon by enzymes to produce needed products. It enables interconversion, such as carbohydrates to fats, maintaining cellular homeostasis. This dynamic pool balances catabolic and anabolic pathways to meet cellular demands.
10. How do secondary metabolites benefit mankind?
Answer: Secondary metabolites, like morphine from poppies, are used in medicine for pain relief and treating diseases. They enhance food flavors (e.g., glucosinolates in cabbage) and act as preservatives due to antibiotic properties. Additionally, compounds like tannins improve astringency in wines and protect plants from pests, benefiting agriculture.
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