Questions
3–4 questions per paper
Difficulty
Easy
Importance
High yield, easy scoring
Overview
Biomolecules encompass the complex organic compounds essential for the structure and function of living organisms, including carbohydrates, proteins, nucleic acids, and vitamins. This topic is a high-yield area in board exams, focusing on the biochemical classification and linkage chemistry of these vital polymers. Understanding their specific functional groups and bonding patterns is crucial for scoring well on memory-based questions.
Carbohydrates
Carbohydrates are polyhydroxy aldehydes or ketones, classified as monosaccharides, disaccharides, and polysaccharides based on hydrolysis. The focus is on the cyclic structures, specifically the Haworth projections of glucose and the glycosidic linkage formed during dehydration.
- Glucose exists in alpha and beta anomeric forms.
- Glycosidic linkage connects two monosaccharide units.
- Reducing sugars exhibit a free hemiacetal or hemiketal group.
- Starch is composed of amylose and amylopectin.
- Cellulose is a linear polymer of beta-D-glucose.
Proteins and Enzymes
Proteins are polymers of alpha-amino acids linked by peptide bonds, essential for biological catalysis and structural integrity. Enzymes are highly specific protein biocatalysts that accelerate reactions by lowering activation energy.
- Amino acids are linked via peptide bonds (-CONH-).
- Zwitterion formation occurs at the isoelectric point.
- Primary structure represents the specific amino acid sequence.
- Denaturation disrupts secondary and tertiary structures.
- Lock-and-key model explains enzyme-substrate specificity.
Nucleic Acids
Nucleic acids, specifically DNA and RNA, are responsible for the storage and transfer of genetic information. They are formed by nucleotides consisting of a nitrogenous base, a pentose sugar, and a phosphate group.
- DNA contains deoxyribose; RNA contains ribose sugar.
- Nitrogenous bases include Purines (A, G) and Pyrimidines (C, T, U).
- Adenine pairs with Thymine via two hydrogen bonds.
- Guanine pairs with Cytosine via three hydrogen bonds.
- Double helix structure is stabilized by hydrogen bonding.
Vitamins
Vitamins are organic compounds required in small quantities for maintaining health and normal biological function, excluding synthesized body requirements. They are categorized based on their solubility in water or fats.
- Fat-soluble vitamins: A, D, E, and K.
- Water-soluble vitamins: B-complex and C.
- Vitamin C deficiency leads to scurvy.
- Vitamin D deficiency causes rickets in children.
- Vitamin K is essential for blood clotting.
Formula Sheet
General formula for carbohydrates: C_x(H_2O)_y
Peptide bond: -CONH-
Glycosidic bond: C-O-C
Exam Tip
Focus on the specific functional group linkages and deficiency diseases, as these are the most frequently asked memory-recall segments.
Common Mistakes
- Confusing the difference between glycosidic, peptide, and phosphodiester linkages.
- Incorrectly identifying which vitamins are fat-soluble versus water-soluble.
- Failing to distinguish between alpha and beta anomers in glucose structure questions.
More Revision Notes
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