• Explain the characteristics of biomolecules such as carbohydrates, proteins, nucleic acids, and hormones.
• Classify carbohydrates, proteins, nucleic acids, and vitamins based on their structures.
• Explain the difference between DNA and RNA.
• Describe the role of biomolecules in biosystems.

Notes on Biomolecules

10.1 Carbohydrates

• Definition: Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis.
• Classification: Broadly classified into three groups:
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Examples: Cane sugar, glucose, starch.
• General Formula: Cₓ(H₂O)ᵥ (e.g., glucose: C₆H₁₂O₆).
• Functions:
  • Energy source for mammals (e.g., glucose from starch digestion).
  • Storage molecules (starch in plants, glycogen in animals).

10.2 Proteins

• Definition: Proteins are polymers of about twenty different α-amino acids linked by peptide bonds.
• Essential Amino Acids: Cannot be synthesized by the body; must be obtained from the diet (e.g., Isoleucine, Arginine).
• Denaturation: Change in pH or temperature can disturb secondary and tertiary structures, affecting function.
• Enzymes: Biocatalysts that speed up reactions; specific to substrates.

10.3 Nucleic Acids

• Definition: Polymers of nucleotides, consisting of a base, a pentose sugar, and a phosphate moiety.
• Types: DNA and RNA.
  • DNA: Contains deoxyribose, double-stranded, includes bases adenine, guanine, cytosine, and thymine.
  • RNA: Contains ribose, single-stranded, includes adenine, guanine, cytosine, and uracil.
• Functions: Genetic information transfer, protein synthesis.

10.4 Vitamins

• Definition: Organic compounds required in small amounts for specific biological functions.
• Classification:
  • Fat-soluble (A, D, E, K)
  • Water-soluble (B group, C)
• Importance: Deficiency can lead to diseases.

10.5 Hormones

• Definition: Molecules acting as intercellular messengers produced by endocrine glands.
• Types: Steroids (e.g., estrogens), polypeptides (e.g., insulin), amino acid derivatives (e.g., epinephrine).
• Functions: Regulate biological activities, maintain homeostasis (e.g., insulin regulates blood glucose levels).

10.6 Key Concepts

• Glycosidic Linkage: Bond between monosaccharides in carbohydrates.
• Peptide Linkage: Bond between amino acids in proteins.
• Denaturation: Loss of protein structure and function due to external stress.
• Complementary Strands: DNA strands are not identical but complementary, crucial for replication.

Common Mistakes and Exam Tips

Common Pitfalls

• Misclassification of Carbohydrates: Students often confuse monosaccharides with disaccharides. Remember that monosaccharides cannot be hydrolyzed further, while disaccharides can yield two monosaccharide units upon hydrolysis.
• Glycosidic Linkage Confusion: Misunderstanding the term glycosidic linkage can lead to incorrect answers. Ensure you know it refers to the bond formed between monosaccharides.
• Denaturation Effects: Students may overlook that denaturation affects secondary and tertiary structures of proteins but leaves the primary structure intact.
• Vitamins Classification: Confusion between fat-soluble and water-soluble vitamins is common. Remember that fat-soluble vitamins (A, D, E, K) can be stored in the body, while water-soluble vitamins (B group and C) cannot.

Exam Tips

• Understand Definitions: Be clear on definitions such as monosaccharides, disaccharides, and glycosidic linkages. Write them out if necessary.
• Practice Classification: Regularly practice classifying carbohydrates and amino acids to avoid mistakes during exams.
• Memorize Key Differences: Focus on the structural differences between DNA and RNA, as well as the functions of different types of RNA.
• Use Diagrams: If applicable, draw diagrams to illustrate concepts like the structure of DNA or the process of denaturation to reinforce your understanding.
• Review Functions of Biomolecules: Make sure you can list and explain the functions of carbohydrates, proteins, and nucleic acids, as these are often exam topics.