Biomolecules — Revision Notes

⚡ 30-Second Revision

Carbohydrates: — $(CH_2O)_n$. Monosaccharides (glucose, fructose), Disaccharides (sucrose, lactose, maltose), Polysaccharides (starch, glycogen, cellulose). Linkage: Glycosidic bond.
Proteins: — Polymers of Amino Acids. Linkage: Peptide bond ($-CO-NH-$). Levels: Primary, Secondary ($alpha$-helix, $\beta$-sheet), Tertiary, Quaternary. Denaturation: Loss of 3D structure.
Nucleic Acids: — DNA, RNA. Monomers: Nucleotides (Base + Sugar + Phosphate). Linkage: Phosphodiester bond. Bases: A, G, C, T (DNA); A, G, C, U (RNA). DNA: Deoxyribose, double helix. RNA: Ribose, single strand.
Lipids: — Hydrophobic. Triglycerides (glycerol + 3 fatty acids), Phospholipids (membrane), Steroids (cholesterol, hormones).
Vitamins: — Essential micronutrients. Fat-soluble (A, D, E, K), Water-soluble (B-complex, C). Deficiency diseases are key.
Enzymes: — Protein catalysts. Lower activation energy. Specific active site. Affected by Temp, pH, Substrate conc. Cofactors/Coenzymes.

2-Minute Revision

Biomolecules are the organic compounds essential for life, categorized into carbohydrates, proteins, nucleic acids, and lipids. Carbohydrates, like glucose, are primary energy sources and form structural components such as cellulose.

They are linked by glycosidic bonds. Proteins, built from amino acids joined by peptide bonds, are the cell's workhorses, performing diverse functions from catalysis (enzymes) to structural support. Their specific 3D structure is crucial, and denaturation leads to loss of function.

Nucleic acids, DNA and RNA, carry genetic information. DNA is a double helix of deoxyribonucleotides, while RNA is typically single-stranded ribonucleotides, both linked by phosphodiester bonds. Lipids are hydrophobic molecules for energy storage, membrane formation, and signaling.

Vitamins are vital micronutrients, classified as fat-soluble (A, D, E, K) or water-soluble (B-complex, C), with specific deficiency diseases. Enzymes, mostly proteins, accelerate reactions by lowering activation energy, exhibiting high specificity and sensitivity to environmental factors like temperature and pH.

5-Minute Revision

Biomolecules are the complex organic compounds that constitute living organisms and mediate all biological processes. They are broadly classified into four major groups:

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Carbohydrates: — These are polyhydroxy aldehydes or ketones, or compounds that yield them upon hydrolysis. They are the primary source of energy. Monosaccharides (e.g., glucose, fructose) are simple sugars. Disaccharides (e.g., sucrose, lactose, maltose) are formed by two monosaccharides linked by a glycosidic bond. Sucrose is a non-reducing sugar. Polysaccharides (e.g., starch, glycogen for storage; cellulose for structure) are long chains of monosaccharides. Starch and glycogen are digestible by humans, while cellulose is not due to $\beta$-1,4-glycosidic linkages.

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Proteins: — These are polymers of amino acids linked by peptide bonds ($-CO-NH-$). There are 20 common amino acids, some of which are essential. Proteins exhibit four levels of structure: Primary (amino acid sequence), Secondary ($alpha$-helix, $\beta$-pleated sheet stabilized by H-bonds), Tertiary (overall 3D shape due to R-group interactions), and Quaternary (arrangement of multiple subunits). Denaturation is the loss of higher-order structures, leading to loss of function.

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Nucleic Acids: — DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) are polymers of nucleotides. Each nucleotide has a nitrogenous base (Purines: Adenine, Guanine; Pyrimidines: Cytosine, Thymine in DNA, Uracil in RNA), a pentose sugar (deoxyribose in DNA, ribose in RNA), and a phosphate group. Nucleotides are linked by phosphodiester bonds. DNA forms a double helix with complementary base pairing (A-T, G-C) and stores genetic information. RNA is typically single-stranded and involved in protein synthesis (mRNA, tRNA, rRNA).

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Lipids: — A diverse group of hydrophobic molecules. Triglycerides (fats/oils) are for energy storage. Phospholipids form cell membranes. Steroids (e.g., cholesterol, hormones) have a characteristic four-ring structure.

Vitamins: Organic compounds required in small amounts. Fat-soluble (A, D, E, K) are stored; Water-soluble (B-complex, C) are excreted. Deficiency leads to specific diseases (e.g., Vitamin A - night blindness, Vitamin C - scurvy, Vitamin D - rickets).

Enzymes: Mostly proteins, acting as biological catalysts. They lower the activation energy of reactions, speeding them up without being consumed. They are highly specific due to their active site and are sensitive to temperature and pH. Cofactors (inorganic ions) and coenzymes (organic molecules, often vitamins) assist enzyme activity.

Example: Glucose, a monosaccharide, can cyclize to form $alpha$-D-glucose and $\beta$-D-glucose. Two glucose units can form maltose (a reducing disaccharide) via an $alpha$-1,4-glycosidic bond. Many glucose units form starch (energy storage) or cellulose (structural). The sequence of amino acids (primary structure) in an enzyme determines its unique 3D shape (tertiary structure), which creates the specific active site for its substrate.

Prelims Revision Notes

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Carbohydrates:

* Monosaccharides: Glucose (aldohexose), Fructose (ketohexose), Galactose. All are reducing sugars. Exist in open-chain and cyclic forms (pyranose/furanose rings). * Disaccharides: Sucrose (Glucose + Fructose) - non-reducing.

Lactose (Glucose + Galactose) - reducing. Maltose (Glucose + Glucose) - reducing. Linkage: Glycosidic bond. * Polysaccharides: Starch (Amylose + Amylopectin) - plant energy storage. Glycogen - animal energy storage (highly branched).

Cellulose - plant cell wall structure ($\beta$-1,4 linkages, indigestible by humans). All are non-reducing.

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Proteins:

* Amino Acids: Building blocks. Zwitterionic nature. Essential vs. Non-essential. General structure: $-NH_2$, $-COOH$, H, R-group on $alpha$-carbon. * Peptide Bond: Amide linkage ($-CO-NH-$) between amino acids.

* Protein Structure: Primary (sequence), Secondary ($alpha$-helix, $\beta$-pleated sheet, H-bonds), Tertiary (3D folding, R-group interactions), Quaternary (multiple subunits). * Denaturation: Loss of 2°, 3°, 4° structure due to heat, pH, etc.

, leading to loss of function.

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Nucleic Acids:

* Components: Nucleotide = Base + Sugar + Phosphate. Nucleoside = Base + Sugar. * Bases: Purines (A, G), Pyrimidines (C, T, U). DNA: A, G, C, T. RNA: A, G, C, U. * Sugars: DNA: Deoxyribose. RNA: Ribose. * Bonds: Phosphodiester bond (backbone), Hydrogen bonds (between bases: A=T, G$equiv$C). * DNA: Double helix, antiparallel strands, stores genetic info. * RNA: Single-stranded, various types (mRNA, tRNA, rRNA), involved in protein synthesis.

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Lipids:

* Triglycerides: Esters of glycerol and 3 fatty acids. Saturated (solid fats), Unsaturated (liquid oils). Energy storage. * Phospholipids: Major component of cell membranes (amphipathic). * Steroids: Four-ring structure (e.g., cholesterol, steroid hormones).

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Vitamins:

* Fat-soluble: A (night blindness), D (rickets), E (antioxidant), K (blood clotting). * Water-soluble: B-complex (various metabolic roles), C (scurvy). Not stored, excreted.

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Enzymes:

* Biological catalysts (mostly proteins). Lower activation energy. Highly specific (active site). * Factors affecting activity: Temperature (optimal, denaturation), pH (optimal, denaturation), Substrate concentration (saturation), Inhibitors, Activators. * Cofactors: Non-protein components (e.g., metal ions, coenzymes like FAD, NAD, derived from vitamins).

Vyyuha Quick Recall

For Fat-Soluble Vitamins (A, D, E, K), remember: KEDA (like 'Keda' is a name). For their deficiency diseases, think of a 'night-rickety-bleeding-eye' for A (night blindness), D (rickets), K (bleeding), E (neurological issues, less common NEET focus). For Purine bases (A, G), remember: 'Pure As Gold' (Purine, Adenine, Guanine). For Pyrimidine bases (C, T, U), remember: 'CUT the Py' (Cytosine, Uracil, Thymine, Pyrimidine).