Carbohydrates

NCERT Reference: NCERT Biology Class 11, Chapter 14: Respiration in Plants, Chapter 15: Plant Growth and Development

Detailed Notes:

Structure and Classification:

• Monosaccharides: Carbohydrates that cannot be hydrolyzed into smaller units. Ex. Glucose, fructose
• Disaccharides: Compounds made up of two monosaccharides joined by a glycosidic bond. Ex. Sucrose, maltose
• Polysaccharides: Composed of many monosaccharide units joined together. Ex. Cellulose, starch, glycogen

Chemical Properties:

• Oxidation: React with oxidizing agents to form various products, like CO2 and H2O. Ex. Glucose + O2 → CO2 + H2O
• Reduction: Can be reduced to form alcohols or other sugar derivatives. Ex. Glucose → Sorbitol (an alcohol)
• Hydrolysis: Break down into smaller units by water in the presence of an acid or enzyme as a catalyst. Ex. Sucrose + H2O → Glucose + Fructose

Biological Functions:

• Energy Storage: Polysaccharides like starch and glycogen store energy in plants and animals, respectively.
• Structural Components: Cellulose provides strength to plant cell walls, while chitin is a structural component in insects and fungi.

Proteins

NCERT Reference: NCERT Biology Class 12, Chapter 12: Reproduction in Organisms, Chapter 13: Strategies for Enhancement in Food Production

Detailed Notes:

Structure and Classification:

• Amino Acids: Building blocks of proteins with a central carbon atom bonded to an amino group, a carboxyl group, a variable side chain, and hydrogen.
• Peptides: Polymers formed by linking amino acids through peptide bonds.
• Primary Structure: Linear sequence of amino acids linked by peptide bonds.
• Secondary Structure: Regular arrangement of amino acids, such as alpha-helix and beta-pleated sheets, stabilized by hydrogen bonds.
• Tertiary Structure: Three-dimensional structure formed by interactions such as hydrogen bonding, disulfide bond formation, and hydrophobic interactions.
• Quaternary Structure: In some proteins, multiple polypeptide chains come together to form a functional protein.

Chemical Properties:

• Ionization: Amino acids have both acidic (carboxyl group) and basic (amino group) properties, allowing them to exist as zwitterions at a particular pH.
• Peptide Bond Formation: Amino acids are linked by peptide bonds through a condensation reaction, releasing a molecule of water.
• Denaturation: Proteins lose their native conformation when subjected to extreme conditions like high temperature, pH changes, or organic solvents.

Biological Functions:

• Enzymes: Proteins that act as catalysts in various biochemical reactions.
• Transport Proteins: Help in the transport of molecules across membranes.
• Structural Proteins: Provide mechanical strength and support, such as collagen in connective tissue.
• Hormones: Chemical messengers that regulate various physiological processes.

Lipids

NCERT Reference: NCERT Biology Class 11, Chapter 12: Mineral Nutrition, Chapter 13: Photosynthesis in Higher Plants

Detailed Notes:

Structure and Classification:

• Fats and Oils: Composed of glycerol bonded to three fatty acids. Saturated fats have only single bonds in their fatty acid chains, while unsaturated fats have one or more double bonds.
• Phospholipids: Consist of glycerol, two fatty acids, and a phosphate group. They are the main components of cell membranes.
• Steroids: Characterized by a four-ring carbon structure and include cholesterol, hormones like testosterone and estrogen, and vitamin D.

Physical and Chemical Properties:

• Hydrophobic Nature: Lipids are generally insoluble in water due to their nonpolar hydrocarbon chains.
• Emulsification: Some lipids, such as phospholipids, can form micelles and emulsions by interacting with both polar and nonpolar molecules.
• Saponification: Lipids react with alkali to form soaps and glycerol through hydrolysis.

Biological Functions:

• Energy Storage: Lipids are a concentrated form of energy storage, providing more energy per unit mass than carbohydrates.
• Insulation: Lipids act as insulators, preventing heat loss in animals.
• Membrane Components: Phospholipids form the lipid bilayer of cell membranes, providing permeability barriers.
• Hormones: Steroids hormones regulate various processes in the body.

Nucleic Acids

NCERT Reference: NCERT Biology Class 12, Chapter 8: Human Health and Disease, Chapter 9: Strategies for Enhancement in Food Production

Detailed Notes:

Structure of Nucleotides and Types:

• Nucleotides: Basic units of nucleic acids, each consisting of a nitrogenous base, a pentose sugar, and a phosphate group.
• DNA: Double-stranded molecule that contains genetic information and serves as the genetic material in most organisms.
• RNA: Single-stranded molecule involved in various cellular processes, including protein synthesis and gene regulation.

Nucleic Acid Structure:

• Double Helix: Structure of DNA where two strands are twisted around each other in a right-handed manner.
• Nucleotides: Building blocks of nucleic acids, consisting of a nitrogenous base, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group.
• Base Pairs: Adenine (A) with thymine (T) in DNA and uracil (U) in RNA, and guanine (G) with cytosine (C) form base pairs through hydrogen bonding, holding the double helix together.

DNA Replication:

• Semi-conservative Replication: During cell division, DNA undergoes replication, where each strand serves as a template to synthesize a new strand.
• Enzymes Involved: Key enzymes involved include DNA polymerase, helicase, and ligase.

Transcription:

• Process of synthesizing RNA molecules using DNA as a template.
• RNA Polymerase: Enzyme that catalyzes the polymerization of RNA nucleotides based on the DNA template.

Translation:

• Process of synthesizing proteins using mRNA as a template.
• Genetic Code: Set of three-nucleotide sequences (codons) that correspond to specific amino acids.
• tRNA: Transfer RNA molecule that carries specific amino acids to the ribosome based on the codon sequence on mRNA.
• rRNA: Ribosomal RNA forms part of the ribosome, a complex structure where translation takes place.

Enzymes:

NCERT Reference: NCERT Biology Class 11, Chapter 14: Respiration in Plants, Chapter 15: Plant Growth and Development

Detailed Notes:

Mechanism of Enzyme Action:

• Active Site: Specific region of an enzyme that binds to the substrate and catalyzes a specific chemical reaction.
• Substrate Binding: Enzymes have high specificity for their substrates, allowing them to bind selectively.
• Enzyme Kinetics: Describes the rate of enzyme-catalyzed reactions and how various factors like temperature and substrate concentration affect enzymatic activity.

Types of Enzymes:

• Oxidoreductases: Catalyze oxidation-reduction reactions, such as dehydrogenases.
• Transferases: Transfer functional groups from one molecule to another, like aminotransferases.
• Hydrolases: Split molecules by adding water at specific bonds, such as amylases.
• Lyases: Catalyze the cleavage of bonds without water addition or hydrolysis, such as decarboxylases.
• Isomerases: Convert one isomeric form of a compound into another, like epimerases.
• Ligases: Join two molecules together with the release of energy, such as DNA ligase.

Enzyme Regulation:

• Allosteric Regulation: Occurs when small molecules bind to specific sites other than the active site, affecting enzyme activity.
• Feedback Inhibition: End products of a metabolic pathway bind to an earlier enzyme, inhibiting its activity to maintain a balance.
• Covalent Modifications: Addition or removal of chemical groups to/from the enzyme, such as phosphorylation or glycosylation, can alter enzyme activity.

Metabolism

NCERT Reference: NCERT Biology Class 11, Chapter 14: Respiration in Plants, Chapter 15: Plant Growth and Development, NCERT Biology Class 12, Chapter 9: Strategies for Enhancement in Food Production, Chapter 10: Microbes in Human Welfare, Chapter 14: Ecosystem

Detailed Notes:

Carbohydrate Metabolism:

• Glycolysis: Breakdown of glucose into smaller molecules like pyruvate, occurring in the cytoplasm under anaerobic conditions.
• Gluconeogenesis: Synthesis of glucose from non-carbohydrate precursors, such as amino acids and fatty acids, mainly occurring in the liver.
• Citric Acid Cycle (TCA Cycle): Central metabolic pathway that involves the oxidation of acetyl-CoA, derived from various sources, and generates ATP, CO2, and reducing equivalents.

Lipid Metabolism:

• β-oxidation: Occurs in mitochondria, where fatty acids are broken down into two-carbon fragments (acetyl-CoA) that enter the TCA cycle for energy generation.
• Lipogenesis: Process of synthesizing fatty acids from acetyl-CoA, mainly happening in the cytoplasm and liver.

Protein Metabolism:

• Deamination: Removal of amino groups from amino acids, forming ammonia.
• Transamination: Transfer of amino groups between amino acids, essential in amino acid interconversions.
• Urea Synthesis (Urea Cycle): Conversion of ammonia to urea in the liver, which is the primary form of nitrogenous waste excretion in humans.

Nucleotide Metabolism:

• Purine Biosynthesis: Synthesis of purine nucleotides like adenine and guanine from precursor molecules like amino acids and ribose-5-phosphate.
• Pyrimidine Biosynthesis: Synthesis of pyrimidine nucleotides like cytosine and uracil from precursors like aspartate and carbamoyl phosphate.