Biology Study Notes: Cell Structure, Respiration, Ecology

List of Drawings - First Year: ✓ Water molecule ✓ Glucose molecule i.e. Monosaccharide ✓ Disaccharide molecule (Glucose + Glucose = Maltose) – You need to be able to draw how maltose forms from two glucose molecules ✓ Formation of a triglyceride (glycerol + 3 fatty acids) ✓ Generalized amino...

List of Drawings - First Year: ✓ Water molecule ✓ Glucose molecule i.e. Monosaccharide ✓ Disaccharide molecule (Glucose + Glucose = Maltose) – You need to be able to draw how maltose forms from two glucose molecules ✓ Formation of a triglyceride (glycerol + 3 fatty acids) ✓ Generalized amino acid ✓ Dipeptide molecule (Amino acid + Amino acid = Dipeptide) – You need to be able to draw how a dipeptide forms from two amino acid molecules ✓ Basic structure of ATP ✓ Structure of a nucleotide ✓ Generalised polynucleotide ✓ Diagram of a mitochondrion ✓ Diagram of a chloroplast ✓ Diagram of a prokaryotic cell ✓ Diagram of a plant eukaryotic cell ✓ Diagram of an animal eukaryotic cell ✓ Diagram of the fluid mosaic model of a cell membrane ✓ ✓ 4 Graphs for each of the 4 factors affecting enzyme action ✓ Structure of the Human heart ✓ Structure of the Human respiratory system ✓ Diagram showing gas exchange in a single alveolus ✓ Diagram of female reproductive system ✓ Diagram of male reproductive system ✓ Sigmoid population growth curve graph ✓ Predator –prey population cycle graph ✓ Carbon cycle ✓ Nitrogen cycle  CELL STRUCTURE AND FUNCTION – DETAILED STUDY NOTES 1. Nucleus Function: Controls cell activities, stores genetic material (DNA), and is the site of RNA synthesis. Structure: Surrounded by a double membrane called the nuclear envelope; contains nucleolus (produces ribosomes). Found in: All eukaryotic cells. 2. Cytoplasm Function: Site of metabolic reactions and holds all organelles. Structure: Jelly-like fluid (cytosol) + organelles. Found in: All cells (prokaryotic and eukaryotic). 3. Cell Membrane (Plasma Membrane) Function: Controls entry and exit of substances; maintains internal balance (homeostasis). Structure: Phospholipid bilayer with embedded proteins (fluid mosaic model). Features: o Selective permeability o Hydrophobic interior blocks water-soluble molecules 4. Mitochondria Function: Powerhouse of the cell – produces ATP via aerobic respiration. Structure: Double membrane; inner membrane folded into cristae; contains its own DNA. Found in: Eukaryotic cells. 5. Ribosomes Function: Site of protein synthesis. Structure: Made of RNA and protein; either free-floating or attached to rough ER. Found in: All cells (prokaryotic and eukaryotic). 6. Rough Endoplasmic Reticulum (RER) Function: Modifies and transports proteins. Structure: Network of membranes with ribosomes on surface. Found in: Eukaryotic cells. 7. Smooth Endoplasmic Reticulum (SER) Function: Synthesizes lipids; detoxifies drugs and poisons. Structure: Similar to RER but lacks ribosomes. Found in: Eukaryotic cells. 8. Golgi Apparatus Function: Modifies, sorts, and packages proteins and lipids for transport. Structure: Stack of flattened membrane sacs. Found in: Eukaryotic cells. 9. Lysosomes Function: Digests waste, damaged organelles, and invaders (contains enzymes). Structure: Membrane-bound vesicles with digestive enzymes. Found in: Mainly animal cells. 10. Vacuole Function: o Plants: Large central vacuole stores water, maintains pressure. o Animals: Smaller vacuoles store nutrients and waste. Structure: Membrane-bound sac. Found in: Both plant and animal cells. 11. Chloroplasts Function: Site of photosynthesis (converts sunlight into glucose). Structure: Double membrane with internal stacks (thylakoids); contains chlorophyll and its own DNA. Found in: Plant cells and some protists. 12. Cell Wall Function: Provides structure and protection. Structure: Made of cellulose in plants; rigid outer layer. Found in: Plant cells, fungi, and some prokaryotes. 1.1 Cellular Respiration ATP – The Cell’s Energy Currency ATP (Adenosine Triphosphate): High-energy molecule used by cells to power processes. Produced during respiration in mitochondria. Aerobic Respiration Requires oxygen Glucose is fully broken down to CO₂ and H₂O. High ATP yield Occurs in mitochondria. Involves: o Glycolysis (in cytoplasm) o Krebs Cycle (in mitochondria) o Electron Transport Chain (inner mitochondrial membrane) Anaerobic Respiration Occurs without oxygen Less efficient: Produces less ATP. By-products: o Lactic acid in animals. o Ethanol + CO₂ in yeast. NAD is regenerated for glycolysis to continue. Glycolysis First step of respiration (in cytoplasm). Glucose → Pyruvate Small ATP gain + NADH produced.  Photosynthesis Location: Chloroplasts (in plant cells) Equation: CO₂ + H₂O + light → C₆H₁₂O₆ + O₂ Light-Dependent Reactions Occur in thylakoid membranes Use sunlight to make ATP and NADPH Light-Independent Reactions (Calvin Cycle) Occur in stroma Use ATP and NADPH to convert CO₂ into glucose Leaf Adaptations Large surface area Thin (for gas exchange) Chloroplast-rich mesophyll Stomata for gas entry/exit 1.2 Cell Theory All living things are made of cells. Cells are the basic unit of life. All cells come from pre-existing cells. Relative Sizes (for scale) Structure Approx. Size Molecule ~1 nm Membrane Thickness ~10 nm Virus ~100 nm Bacteria ~1 µm Organelle ~10 µm Cell ~100 µm Surface Area: Volume Ratio  Smaller cells have a higher surface area to volume ratio, allowing better exchange of materials. 1.3 Prokaryotic Cells (e.g., Bacteria) Key Features and Their Functions Ribosomes – Make proteins Slime Capsule – Protection from environment Cell Wall – Shape and protection Flagellum – Movement Plasmid – Small circular DNA, used in genetic engineering Naked DNA – Free-floating genetic material Cell Membrane – Controls entry/exit of materials 1.4 Eukaryotic Cells (Plants and Animals) Key Differences from Prokaryotes Have a nucleus Contain membrane-bound organelles Larger in size Plant vs Animal Cells Feature Plant Animal Cell Wall Chloroplasts Vacuole Large Small Lysosomes Rare Common 1.5 Cell Membranes Fluid Mosaic Model Phospholipid bilayer: Hydrophilic heads, hydrophobic tails Embedded proteins: Transport, receptors Cholesterol: Adds fluidity (not required in detail) Glycoproteins: Cell recognition (not required in detail) Transport Across Membranes  Diffusion: Passive; movement of molecules from high to low concentration. Osmosis: Diffusion of water across a membrane. Active Transport: Requires energy (ATP); moves substances against concentration gradient using protein carriers. TOPIC 2: THE CHEMISTRY OF LIFE 2.1 Atoms, Ions, and Molecules Atoms: Basic units of matter made of protons, neutrons, and electrons. Ions: Atoms or molecules with an electric charge (lost/gained electrons). Most common elements in life: Carbon (C), Hydrogen (H), Oxygen (O) Others: Nitrogen (N), Phosphorus (P), Sulfur (S), Iron (Fe), Potassium (K) 2.2 Water Properties of Water: 1. Transparency – Allows light to pass for aquatic photosynthesis. 2. Cohesion – Water molecules stick together (important in plant transport). 3. Surface Tension – Allows small organisms to sit or move on water. 4. Solvent – Dissolves many substances; important for transport in cells. 5. Thermal Stability – High heat capacity helps maintain stable environments. Importance of Water in Biology: Coolant: Sweat evaporates to cool the body. Transport: Moves nutrients in blood and xylem/phloem. Habitat: Aquatic life depends on water’s properties. 2.3 Biomolecules Organic Compounds Carbon-based molecules found in living organisms. Proteins  Made of: Amino acids (20 types) Link: Peptide bonds (via condensation reactions) Dipeptide = 2 amino acids Polypeptide = Many amino acids Protein Functions: Structural: Collagen, keratin Movement: Muscle proteins Transport: Hemoglobin Enzymes: Speed up reactions Carbohydrates Basic units: Monosaccharides (e.g. glucose) Can form: o Disaccharides (e.g. sucrose = glucose + fructose) o Polysaccharides (e.g. starch, glycogen, cellulose) Functions: Glucose & Fructose: Quick energy Sucrose: Transported sugar in plants Starch: Energy store in plants Glycogen: Energy store in animals Cellulose: Plant cell wall structure Lipids (Fats and Oils) Made of glycerol + fatty acids Linked by ester bonds via condensation Triglyceride: 1 glycerol + 3 fatty acids Functions: Long-term energy storage Cell membrane structure (phospholipids) Insulation and protection Condensation & Hydrolysis Condensation: Joins monomers, releases water. Hydrolysis: Breaks bonds using water.  Solubility of Biomolecules Carbohydrates: Mostly soluble Proteins: Some soluble Lipids: Insoluble in water (hydrophobic) Energy Content (Qualitative) Lipids > Proteins > Carbohydrates (per gram) 2.4 Enzymes Definition: Biological catalysts that speed up reactions. Active Site: Specific part of enzyme where substrate binds. Lock-and-Key Model Only the correct substrate fits into the enzyme’s active site (like a key in a lock). Factors Affecting Enzyme Activity: 1. Temperature – Too high = denatured; too low = slow activity. 2. pH – Each enzyme has an optimum pH. 3. Inhibitors – Block or slow enzyme activity. 4. Substrate Concentration – More substrate = faster reaction (until saturation). TOPIC 4: ECOLOGY (Detailed Study Notes – IM Biology 05) 4.1 Basic Ecological Concepts Key Definitions: Ecology: Study of interactions between organisms and their environment. Ecosystem: A community of organisms + their physical environment. Population: All individuals of one species in an area. Community: All populations living together in an area.  Species: A group of organisms that can interbreed and produce fertile offspring. Biosphere: All ecosystems on Earth. Habitat: Natural environment where an organism lives. Relationships in Ecosystems Competition: Organisms compete for limited resources (e.g. food, space). Predation: One organism hunts and eats another. Parasitism: One benefits, the other is harmed (e.g. flea on a dog). Food Chains and Webs Food Chain: A linear flow of energy (e.g. grass → rabbit → fox). o Arrows show energy flow: A → B means "A is eaten by B". Food Web: Complex network of many food chains. Trophic Levels: 1. Producers (Autotrophs) – Make food (e.g. plants) 2. Primary Consumers – Eat producers (e.g. herbivores) 3. Secondary Consumers – Eat primary consumers 4. Tertiary Consumers – Top predators Definitions: Autotroph: Makes its own food (e.g. plants) Heterotroph: Eats other organisms (e.g. animals) Detritivore: Eats dead material (e.g. earthworms) Saprotroph (Decomposer): Breaks down dead organisms externally (e.g. fungi, bacteria) 4.2 Energy Relationships Energy Flow: Starts with the sun → transferred through trophic levels. Only 10-20% of energy is passed on to the next level (the rest is lost as heat or waste). Pyramids:  Pyramid of Energy: Shows energy at each trophic level (always a pyramid shape). Pyramids of numbers and biomass: Not required for this syllabus. Nutrient Cycling Carbon Cycle: Photosynthesis: Plants absorb CO₂. Respiration: Organisms release CO₂. Combustion: Burning fossil fuels releases CO₂. Fossilisation: Dead organisms form fossil fuels over time. Nitrogen Cycle: Decomposers (saprotrophs) break down dead matter, returning nitrogen to the environment in inorganic form. 4.3 Populations Population Size is Affected by: Natality (birth rate) ↑ Immigration (entering) ↑ Mortality (death rate) ↓ Emigration (leaving) ↓ Population Growth Curve: 1. Exponential Phase – Rapid growth. 2. Transitional Phase – Growth slows due to limited resources. 3. Plateau Phase – Population stabilizes. Carrying Capacity: Maximum number of individuals an environment can support. Human Impact: Pollution, habitat loss, and global warming disrupt ecosystems. Must study at least two examples, one being the increased greenhouse effect TOPIC 5: EVOLUTION AND DIVERSITY OF LIFE 5.1 Evolution and Diversity Key Concepts: Variation: Members of a species show genetic differences. Overproduction: More offspring are produced than can survive. Competition: Limited resources lead to struggle for survival. Natural Selection: Best-adapted individuals survive, reproduce, and pass on genes. Summary: Evolution is driven by natural selection acting on variations. Diversity of Life – The Five Kingdoms 1. Prokaryota (e.g. Bacteria) No nucleus No membrane-bound organelles Simple, small cells Have cell walls 2. Protoctista (e.g. Algae, Amoeba) Mostly unicellular eukaryotes No complex organ systems Often aquatic Can be plant-like (e.g. algae) or animal-like (e.g. protozoa) 3. Fungi (e.g. Mushrooms, Mould) Made of hyphae Saprotrophic: absorb nutrients from decaying matter Cell walls made of chitin Mostly multicellular 4. Plantae (e.g. Flowering plants) Photosynthetic Cell walls made of cellulose  Most have vascular tissues (xylem/phloem) Terrestrial habitat 5. Animalia (e.g. Insects, Humans) No cell walls Multicellular Heterotrophic Capable of movement and fast response to stimuli TOPIC 6: HUMAN HEALTH AND PHYSIOLOGY The Heart 4 Chambers: Right atrium, right ventricle, left atrium, left ventricle. Valves: Prevent backflow: o Atrioventricular (AV) valves o Semilunar valves Circulation: o Blood enters atria → pumped by ventricles → arteries. o Right side: sends deoxygenated blood to lungs. o Left side: sends oxygenated blood to the body. Control of Heartbeat Heart beats automatically (myogenic). Nerves and hormones adjust rate based on activity. Blood Vessels Vessel Function Key Features Arteries Carry blood away from heart Thick walls, small lumen, high pressure Veins Carry blood to the heart Thin walls, valves, large lumen Vessel Function Key Features Capillaries Exchange materials with tissues One-cell thick walls Tissue Fluid Formed from plasma that leaks out of capillaries. Enables exchange of gases and nutrients between blood and cells. Components of Blood Plasma: Carries dissolved substances (nutrients, hormones, CO₂, waste) Erythrocytes (Red Blood Cells): Carry oxygen (via haemoglobin) Leucocytes (White Blood Cells): Defend against disease Platelets: Help blood clotting Transport Roles Carries: oxygen, nutrients, hormones, waste, heat, and antibodies 6.3 Defence Against Infectious Disease Pathogens Microorganisms that cause disease (e.g. bacteria, viruses) First Line of Defence Skin: Physical barrier Mucous membranes: Trap pathogens in lungs and gut Second Line of Defence Phagocytic leucocytes: Engulf and destroy pathogens Third Line of Defence – Immune System Antigens: Foreign substances that trigger immune response Antibodies: Proteins that bind to specific antigens B Lymphocytes: Produce antibodies Form memory cells for future protection Vaccines and Antibiotics Vaccines: Stimulate antibody production without causing illness. Antibiotics: Kill bacteria (not viruses). HIV and AIDS HIV attacks T-helper cells → weakens immune response. Leads to AIDS, making the body vulnerable to infections. Gas Exchange System Main Parts: Trachea: Windpipe; connects throat to lungs. Bronchi: Two branches leading into each lung. Bronchioles: Smaller airways inside lungs. Alveoli: Tiny air sacs where gas exchange occurs. How It Works Inhalation: Air enters → oxygen diffuses into blood at alveoli. Exhalation: CO₂ from blood diffuses into alveoli → breathed out. Alveoli Adaptations (for efficient gas exchange): 1. Large surface area – maximizes exchange. 2. Thin walls – short diffusion distance. 3. Moist lining – gases dissolve easily. 4. Rich blood supply – maintains diffusion gradient. Ventilation System Required to maintain a constant supply of fresh oxygen and removal of CO₂. Breathing (ventilation) is not the same as cellular respiration.  Health Problems (example conditions): Asthma: Narrowed airways cause difficulty breathing. Emphysema: Damaged alveoli reduce gas exchange. Smoking: Destroys alveoli and reduces oxygen uptake. 6.7 Reproduction Sexual Reproduction Involves two parents. Increases genetic variation. Male Reproductive System: Testes: Produce sperm and testosterone. Sperm ducts: Transport sperm. Penis: Delivers sperm into female body. Female Reproductive System: Ovaries: Produce eggs and hormones (oestrogen & progesterone). Oviducts (fallopian tubes): Where fertilisation happens. Uterus: Where fetus develops. Vagina: Receives sperm. Hormones and Menstrual Cycle: Hormone Role FSH (Follicle-Stimulating Hormone) Stimulates egg development and oestrogen production LH (Luteinising Hormone) Triggers ovulation Oestrogen Thickens uterus lining Progesterone Maintains uterus lining Testosterone (in males) Develops male characteristics & sperm production Fertilisation  Fusion of sperm and egg nuclei → forms zygote Zygote develops into embryo and then fetus Pregnancy Support Amniotic sac and fluid protect the fetus.