CET SAIL Science Biology Volumes 2 Study Notes

BRANCHES OF BIOLOGY

Biology: The scientific study of living things.
Botany: The study of plants.
Zoology: The study of animals.
Anatomy: The study of the structures of living organisms, typically involving dissection.
Physiology: The study of the mechanisms and functions of the human body.
Genetics: The study of the inheritance of traits passed from parents to offspring.
Immunology: The study of the immune system, including its components, biological processes, physiological functioning, types of immunity, and related disorders.
Microbiology: The study of various microscopic organisms such as bacteria and fungi.
Biotechnology: The use of technology to modify and manipulate biological systems.
Ecology: The study of organisms, their environment, and the interactions between organisms and their surroundings.
Taxonomy: The branch of biology dealing with naming, describing, and the classification of all living organisms.

THE CELL: THE SMALLEST UNIT OF LIFE

Definition: The cell is the smallest unit of life and serves as the building blocks of all organisms.
Levels of Biological Organization: - Cells \u2192 Tissues \u2192 Organs \u2192 Organ Systems \u2192 Organisms.
Common Parts in ALL Cells: - Plasma membrane: The outer boundary. - Cytoplasm: The internal jelly-like fluid. - Ribosomes: The site of protein synthesis. - DNA: The genetic material.
Classification of Cells: - Prokaryotic: - Found in domains Archaea and Bacteria. - Lacks a nucleus. - No membrane-bound organelles. - DNA is not membrane-bound. - Eukaryotic: - Found in domain Eukarya. - Has a distinct nucleus containing DNA. - Contains membrane-bound organelles.
Plant Cells vs. Animal Cells: - Plant Cells: Possess a cell wall, chloroplasts for photosynthesis, and a large central vacuole. - Animal Cells: Possess centrosomes and lysosomes; lack a cell wall and chloroplasts.

CELL ORGANELLES AND STRUCTURES

Nucleus: - Nuclear envelope: A membrane enclosing the nucleus with protein-lined pores for material transport. - Chromatin: DNA plus associated proteins. - Nucleolus: A condensed region within the nucleus where ribosomes are formed.
Organelles found in Animal Cells: - Peroxisome: Metabolizes waste. - Endoplasmic Reticulum (ER): - Rough ER: Associated with ribosomes; creates secretory and membrane proteins. - Smooth ER: Responsible for lipid synthesis. - Golgi Apparatus: Modifies, sorts, and packages proteins. - Mitochondria: The primary site of energy production (ATP). - Lysosome: Responsible for digesting food and waste materials. - Vacuole: Membrane-bound storage sac.
Organelles and Structures in Plant Cells: - Plasmodesmata: Channels that connect two plant cells, allowing their cytoplasms to link. - Cell Wall: Maintains cell shape and provides structural support. - Central Vacuole: Filled with cell sap; maintains pressure against the cell wall. - Plastid: Stores pigments. - Chloroplast: The site of photosynthesis.
The Endomembrane System: A set of organelles and membranes involved in the production, modification, and delivery of lipids and proteins. It includes: 1. Nuclear membrane 2. Rough endoplasmic reticulum 3. Smooth endoplasmic reticulum 4. Golgi apparatus 5. Lysosomes and transport vesicles 6. Plasma membrane
Cytoskeleton: A network of protein fibers with four primary functions: maintaining cell structure, allowing movement of vesicles and cytoplasm, allowing cell movement, and anchoring organelles. It consists of: - Microfilaments: Narrowest diameter ( $7\,nm$ ); composed of two strands of actin chains interacting with myosin; allows cells to change shape and move. - Intermediate Filaments: Intertwined protein fibers ( $8-10\,nm$ diameter); made of proteins like keratin; maintains cell structure and anchors organelles. - Microtubules: Hollow tubes of globulin proteins ( $25\,nm$ diameter); acts as tracks for vesicles and pulls chromosomes apart during cell division.

CELL MEMBRANE AND TRANSPORT

The Fluid Mosaic Model: Describes the cell membrane as a mosaic of phospholipids, proteins, and carbohydrates, giving it structural integrity and fluidity.
Plasma Membrane Components: - Phospholipid: The main membrane fabric arranged in two layers. Consists of a hydrophilic phosphate head on the surface and a hydrophobic tail on the inside. - Cholesterol: Attached between phospholipids to regulate fluid characteristics. - Integral Proteins: Embedded within the phospholipid layers (e.g., integrins); can penetrate through both layers. - Peripheral Proteins: Located on the inner or outer surface of the bilayer; not embedded. - Carbohydrates: Attached to proteins (glycoproteins) or lipids (glycolipids) on the outside membrane; act as identifiers for cell communication.
Passive Transport: Follows the concentration gradient (high to low) without energy expenditure. - Diffusion: Movement of solutes from high to lower concentration. - Heavier/larger molecules move slower. - Higher concentration gradient leads to faster diffusion. - Osmosis: Movement of water through a semipermeable membrane until concentrations are equalized. - Hypotonic: Less concentrated outside; water enters cell; cell may burst (lyse). - Isotonic: Equal concentrations; no net water movement. - Hypertonic: Higher concentration outside; water leaves cell; cell shrivels. - Facilitated Transport: Uses transport proteins for polar molecules. - Channel Protein: Integral protein; may be gated to control flow (e.g., water through aquaporins). - Carrier Protein: Binds to a substance and changes shape to push it inside the cell.
Active Transport: Moves against the concentration gradient; requires energy (ATP). - Primary Active Transport: ATP binds directly to a protein to transfer a substance (e.g., the sodium-potassium pump). - Secondary Active Transport (Co-Transport): Uses the potential energy from one molecule moving down its gradient to transport another (e.g., glucose transport).
Bulk Transport: - Endocytosis: Transporting into the cell. - Phagocytosis: For large particles; membrane envelopes particle into a vesicle (later digested by lysosomes). - Pinocytosis: For smaller molecules/liquids. - Receptor-mediated endocytosis: Specific molecules bind to receptors to trigger engulfment. - Exocytosis: Transporting out of the cell; vesicles fuse with the membrane and release contents.

CELLULAR ENERGY AND METABOLISM

Cell Interactions: - Extracellular Matrix (ECM): A network of collagen and carbohydrate fibers outside animal cells that holds cells together and aids communication. - Intercellular Junctions: - Plasmodesmata: (Plants) Channels connecting cytoplasm. - Tight junctions: (Animals) Watertight seals between cells. - Gap junctions: (Animals) Channels allowing transport between cells. - Desmosomes: (Animals) Connect cells via intermediate filaments (keratin).
Cellular Respiration: - Glycolysis: - Energy-requiring steps (1-5): $2\,ATP$ consumed. - Energy-releasing steps (6-10): $4\,ATP$ produced. - Pyruvate Oxidation: Occurs in the mitochondrion. Pyruvate is converted to Acetyl CoA, releasing $CO_2$ and creating NADH from NAD+. - Citric Acid Cycle: Further breakdown of molecules. - Oxidative Phosphorylation (Electron Transport Chain): Only part that uses oxygen; produces the most ATP.
Metabolism without Oxygen: - Anaerobic respiration: Uses molecules other than oxygen for the electron transport chain. - Lactic acid fermentation: Pyruvate is reduced to lactate to regenerate NAD+. - Equation: $\text{Pyruvic Acid} + \text{NADH} \rightleftharpoons \text{Lactic Acid} + \text{NAD}^+$ - Alcohol fermentation: Regenerates NAD+ by producing ethanol and $CO_2$ .

LIFE FUNCTIONS

Metabolism: Essential chemical reactions including combining simple molecules into complex ones (anabolism) and breaking complex substances down (catabolism).
Reproduction: Producing offspring. - Asexual: One parent; no sex cells. Example: Budding (a bud detaches from parent, e.g., sponges). - Sexual: Two parents; union of sex cells (egg and sperm) via fertilization.
Responsiveness/Sensitivity: Responding to internal or external stimuli.
Movement: Motion of the body, organs, or individual cells.
Development: Changes throughout life, including growth, repair, and differentiation.
Homeostasis: Maintaining a stable internal environment.
Excretion: Removal of waste products.
Nutrition: Exchange of materials and gases with the environment.

BIOLOGY OF PLANTS

Plant Systems: - Shoot system: All parts above ground. - Root system: All parts underground.
Plant Tissues: - Meristematic: Constantly dividing cells for growth. - Apical meristems: Responsible for Primary Growth (taller/longer). - Lateral meristems: Responsible for Secondary Growth (thicker/wider); includes vascular cambium (secondary xylem/phloem) and cork cambium. - Permanent: No longer constantly dividing; specialized into Dermal (epidermis), Ground (cortex, pith, mesophyll), and Vascular (xylem, phloem).
Photosynthesis: - Overall location: Chloroplast. - Light-Dependent Reaction: Occurs in the thylakoid. - Water ( $H_2O$ ) is input; Oxygen ( $O_2$ ) is released. - ATP and NADPH are produced. - Uses Photosystem II and Photosystem I. - Calvin Cycle (Light-Independent): Occurs in the stroma. - Phase 1: Carbon Fixation ( $CO_2$ is fixed by RuBP and Rubisco). - Phase 2: Reduction (ATP and NADPH are used to produce G3P). - Phase 3: Regeneration of RuBP. - Output: Glucose ( $C_6H_{12}O_6$ ) and other organic compounds.
Transport in Plants: - Water Transport: Explained by the Cohesion-Tension Theory; pulls water up through the xylem. - Nutrient Transport: Source to Sink; driven by water moving from xylem to phloem near sources (osmosis), pushing nutrients throughout the plant.
Essential Elements: - Macronutrients (needed in large amounts): $C, H, O, N, P, K, Ca, Mg, S$ . - Micronutrients (needed in trace amounts): $Fe, Mn, B, Mo, Cu, Zn, Cl, Ni, Co, Na, Si$ .
Plant Hormones: - Growth Promoters: Auxins, Gibberellins, Cytokinins. - Growth Inhibitors: Abscisic Acid. - Both: Ethylene.
Tropisms (Growth Responses): 1. Hydrotropism: Response to water. 2. Gravitropism/Geotropism: Response to gravity. 3. Phototropism: Response to light. 4. Thigmotropism: Response to touch.
Plant Reproduction: - Asexual: Offspring from vegetative parts (leaf, stem, root); no seeds. - Methods: Budding, fragmentation, vegetative propagation, spore formation. - Sexual: Through reproductive parts (flowers); forms fruits and seeds. - Flower Parts: Stamen (Anther, Filament), Pistil/Carpel (Stigma, Style, Ovary, Ovule), Petal (Corolla), Sepal (Calyx). - Pollination: Transfer of pollen grains from anther to stigma.

ORGANIC AND INORGANIC COMPOUNDS

Organic Compounds: Main chemical compounds in living organisms, typically containing C-H bonds. They are composed of units called monomers. - Carbohydrates: Store energy ( $C, H, O$ ). - Monosaccharides: Glucose, fructose, galactose. - Disaccharides: Sucrose (G+F), maltose (G+G), lactose (G+Ga). - Polysaccharides: Starch (plants), Glycogen (animals), Cellulose. - Proteins: Perform varied functions determined by amino acid sequence ( $C, H, O, N, S$ ). - Examples: Enzymes (reactions), Antibodies (protection), Muscle fiber (movement). - Monomer: Amino Acids. - Lipids: Fats, oils, waxes, steroids ( $C, H, O, P$ ). - Fats: Solid at room temp; long-term energy for animals. - Oils: Liquid at room temp; long-term energy for plants. - Waxes: Water-resistant protective coverings. - Phospholipids: Essential for membranes. - Nucleic Acids: Carry hereditary information ( $C, H, O, P, N$ ). - DNA: Double-stranded; stores genetic info. - RNA: Involved in protein synthesis. - ATP: Energy currency.
Inorganic Compounds: Lack C-H bonds. - Water ( $H_2O$ ): Most abundant inorganic compound. - Minerals: Crystalline structures from geological processes. - Acids and Bases: - Acids: pH ranges from $1$ to $7$ ; donate $H^+$ ions; turn blue litmus red; sour taste (e.g., $HCl, H_2SO_4$ ). - Bases: pH ranges from $7$ to $14$ ; donate $OH^-$ ions; turn red litmus blue; bitter taste and soapy feel (e.g., $NaOH, KOH$ ). - Neutral: pH of approximately $7$ (e.g., water).