GRADE 12 BIOLOGY NOTES.docx

UNIT 1 1.1 Fundamentals Chemistry Of Life

• Isotopes: Forms of elements that differ in the number of neutrons.

• Radioactive isotopes: Unstable isotopes whose nuclei spontaneously break down.

Ionic Bonding

• Involves non-metals with metals, resulting in electron transfer.

• Losing electrons creates a positively charged ion (cation).

• Gaining electrons creates a negatively charged ion (anion).

Covalent Bonding

• Involves non-metals with non-metals, resulting in electron sharing.

• Electronegativity: Measure of an atom's ability to attract shared electrons.

  • Polar Covalent Bonds: Electrons are shared unequally due to higher electronegativity of one atom.

  • Non-polar Covalent Bonds: Electrons are shared equally when electronegativities are similar.

Forces Influencing Bonds

• Intramolecular Bonds: Bonds within a molecule.

• Intermolecular Bonds: Forces between molecules, such as:

  • Van der Waals forces: Weak attractions due to temporary dipoles.

  • Dipole-Dipole forces: Attractions between polar molecules.

  • Hydrogen Bonds: Strong attractions between electronegative atoms (N, O, F) and hydrogen.

Reaction Types

• Dehydration/Condensation Reaction: Combines smaller units into larger molecules by removing water.

• Hydrolysis Reaction: Breaks larger molecules into subunits by adding water.

• Neutralization Reaction: Reaction between an acid and base to form salt and water.

• Redox Reaction: Involves the transfer of electrons from one atom to another and is essential for energy transfers in cells.

Water

• Hydrophilic: Polar/charged molecules strongly attracted to water.

• Hydrophobic: Non-polar molecules weakly attracted to water.

Acids and Bases

• Acids: Increase [H+] in solution; taste sour and turn litmus paper red.

• Bases: Increase [OH-]; taste bitter, feel slippery, and turn litmus paper blue.

• Buffers: Chemicals that stabilize pH by accepting/donating H+ ions (e.g., in human blood).

UNIT 1 1.3 Carbon Chemistry Of Life

• Functional Groups: Clusters of atoms that determine the behavior of organic molecules.

Dehydration (Condensation) Reaction

• Involves the removal of H and OH groups from two molecules to form a larger one, releasing water.

• Hydrolysis: Breakdown of macromolecules by adding water.

UNIT 1 1.4 Carbohydrates and Lipids

• Carbohydrates consist of C, H, O in a 1:2:1 ratio (C6H12O6 = glucose).

• Monomers: Single units (e.g., monosaccharides like glucose).

• Polymers: Chains of monomers (e.g., polysaccharides - cellulose, starch).

  • Glycosidic Linkage: Covalent bond joining monosaccharides.

• Lipids: Composed mainly of C and H, with fewer O atoms, and are hydrophobic.

  • Triglycerides: Composed of glycerol and three fatty acids; main energy storage in vertebrates.

  • Phospholipids: Major constituents of cell membranes, consisting of glycerol, two fatty acids, and a phosphate group.

  • Steroids: Four fused hydrocarbon rings; include cholesterol and various hormones.

UNIT 1 1.5 Proteins & Nucleic Acids

Proteins

• Functions: Enzymatic reactions, structural support, transport, muscle movement, and immune response.

• Composed of 20 amino acids; 9 essential and 11 non-essential.

• Amino acids connected by peptide bonds.

• Protein folding levels:

  1. Primary: Sequence of amino acids.

  2. Secondary: Alpha helices or beta sheets stabilized by H-bonds.

  3. Tertiary: Further folding due to side chain interactions.

  4. Quaternary: Interaction between multiple polypeptide chains.

Nucleic Acids

• DNA: Stores genetic information, composed of nucleotides.

  • Structure: Double helix, complementary base pairs (A-T, G-C).

• RNA: Assists in protein synthesis and gene expression.

  • Single-stranded and contains uracil instead of thymine.

UNIT 1 1.7 Enzymes

• Biological catalysts that lower activation energy for reactions.

• Active Sites: Specific regions where substrates bind.

• Enzyme-Substrate Complex: Formed when enzyme binds to substrate.

• Factors Affecting Activity: Temperature, pH, substrate concentration, inhibitors, activators.

UNIT 2 2.1 Cell Structure and Function

• Cell Membrane: Composed of a lipid bilayer with embedded proteins, regulates transport and cell interaction.

• Mitochondria: Site of ATP production; double membrane structure.

• Cytoplasm: Fluid that contains organelles.

UNIT 2 2.2 Membrane Structure and Function

• Fluid Mosaic Model: Describes the dynamic structure of the cell membrane.

• Transport Mechanisms: Passive (no energy required) and active (requires ATP).

  • Passive Transport: Diffusion and osmosis.

  • Active Transport: Uses ATP to move substances against their gradients.

Membrane- Assisted Transport

• Endocytosis: Process of taking in materials by folding the membrane inward.

• Exocytosis: Process of expelling materials from the cell via vesicles.

UNIT 3 3 Intro to Metabolism

• Redox Reactions: Involve electron transfer, crucial for cellular energy production.

• ATP: Main energy currency in cells; produced during cellular respiration processes.

UNIT 4 4.1 Cellular Respiration

• Four metabolic pathways: Glycolysis, Pyruvate oxidation, Krebs cycle, and Electron Transport Chain.

  • Glycolysis: Splits glucose into pyruvate, yielding some ATP.

  • Citric Acid Cycle (Krebs Cycle): Further processes pyruvate for electron carriers (NADH and FADH2).

  • Electron Transport Chain: Uses electrons from carriers to produce ATP through chemiosmosis.

UNIT 4 4.2 Photosynthesis

• Overview: Converts solar energy into chemical energy (glucose).

• Two main stages: Light-dependent reactions and light-independent reactions (Calvin Cycle).

• Pigments: Absorb light for photosynthesis (chlorophyll, carotenoids).

• Calvin Cycle: Uses ATP and NADPH from light reactions to synthesize glucose.

UNIT 5 5.1 Introduction To Photosynthesis

• Describes the relationship between photosynthesis and cellular respiration.