BTEC Level 3 Applied Science – COMPLETE Biology Revision Pack This is your main revision guide based on all the B1, B2 and B3 notes you shared and everything we’ve been practising. It includes: * All the main topics you need to revise. * Definitions and key scientific terms. * Cell structures and their functions. * Specialised cells and immunity. * Tissues, lungs and circulation. * Muscles and the nervous system. * ECGs. * 6-mark practice questions. * Mnemonics with every letter explained. * Exam-ready answers. Important: Nobody can guarantee the exact questions that will come up. This covers the topics in your notes, including likely extended-answer areas. Use your official unit specification and teacher’s guidance alongside it. PART 1 – B1: CELL STRUCTURE 1. Levels of organisation Learn these definitions: Term Definition Cell Basic structural and functional unit of life. Tissue Group of similar specialised cells working together. Organ Different tissues working together to perform a function. Organ system Different organs working together. Organelle Specialised structure inside a cell. Mnemonic: Cats Take Over Sofas * Cats = Cells * Take = Tissues * Over = Organs * Sofas = Systems Order: Cell → Tissue → Organ → Organ system. 2. Differentiation Definition: Differentiation is when an unspecialised cell develops into a specialised cell to perform a particular function. Examples: * A stem cell can become a red blood cell. * A stem cell can become a neurone. * A stem cell can become a muscle cell. 3. Prokaryotic cells Prokaryotes are cells without a nucleus. Learn these structures: Structure Function Nucleoid Contains circular DNA. Plasmids Small extra rings of DNA. 70S ribosomes Protein synthesis. Capsule Protection and attachment. Cell wall Made of peptidoglycan; provides support. Cell membrane Controls substances entering and leaving. Cytoplasm Where chemical reactions occur. Mnemonic: Naughty Pigs Rarely Chase Wolves * N = Nucleoid * P = Plasmids * R = Ribosomes * C = Capsule * W = Wall Remember: Prokaryotes do not have a nucleus or membrane-bound organelles. 4. Eukaryotic cells Eukaryotic cells have: * A nucleus. * 80S ribosomes in the cytoplasm. * Membrane-bound organelles. Plant cells Structure Function Cellulose cell wall Support and protection. Chloroplasts Photosynthesis. Permanent vacuole Contains cell sap and helps maintain turgor. Tonoplast Membrane surrounding the vacuole. Amyloplasts Store starch. Plasmodesmata Connections between neighbouring plant cells. Pits Areas where the cell wall is thinner. Animal cells Animal cells can contain: * Nucleus. * Mitochondria. * Ribosomes. * Cell membrane. * Cytoplasm. * Centrioles. * Glycogen stores. Animal cells do not have cellulose cell walls or chloroplasts. 5. Organelles and their functions Organelle Function Cell membrane Controls movement of substances. Cytoplasm Site of many chemical reactions. Nucleus Contains DNA and controls cell activities. Nucleolus Produces ribosomal components. Ribosomes Protein synthesis. Rough ER Transports and processes proteins. Smooth ER Lipid and steroid synthesis. Golgi apparatus Modifies, sorts and packages proteins. Vesicles Transport substances. Lysosomes Contain digestive enzymes. Mitochondria Aerobic respiration and ATP production. Centrioles Help organise spindle fibres during cell division. Chloroplasts Photosynthesis. Identifying organelles in micrographs * Mitochondria: oval shape with folded inner membranes called cristae. * Nucleus: large structure with a double membrane and pores. * Rough ER: flattened membranes with ribosomes attached. * Chloroplast: contains stacks of membranes called grana. * Golgi: curved, flattened membrane sacs. * Bacteria: no nucleus; DNA lies free in the cytoplasm. 6. Light and electron microscopes Light microscope Electron microscope Uses light. Uses an electron beam. Lower resolution. Higher resolution. Lower magnification. Higher magnification. Can view living cells. Specimens must be dead. Can show natural colours. Original images are monochrome. Generally cheaper. Generally more expensive. Mnemonic: M R C L * M = Magnification * R = Resolution * C = Colour * L = Living specimens 7. Magnification calculations Learn these three formulas: M=\frac{I}{A}I=M\times AA=\frac{I}{M} Where: * M = Magnification * I = Image size * A = Actual size Conversions: * 1 mm = 1000 µm * 1 µm = 1000 nm Always make sure your measurements use the same units. Stage micrometer and eyepiece graticule A graticule is calibrated against a stage micrometer. Mnemonic: Lazy Chefs Dice Meat * L = Line up the scales. * C = Count the divisions. * D = Divide the known measurement by the number of divisions. * M = Measure the specimen. Recalibrate when changing magnification. PART 2 – GRAM STAINING AND ANTIBIOTICS 8. Gram-positive and Gram-negative bacteria Gram-positive Gram-negative Thick peptidoglycan wall. Thin peptidoglycan wall. No outer membrane. Has an outer membrane. Stains purple. Stains pink/red. Generally more susceptible to penicillin. Outer membrane provides additional protection. 9. Gram staining Mnemonic: Hot Cats In Autumn Spring * Hot = Heat-fix: Fix bacteria onto a microscope slide. * Cats = Crystal violet: Add purple dye. * In = Iodine: Helps retain the crystal violet. * Autumn = Alcohol: Removes the dye from Gram-negative bacteria. * Spring = Safranin: Counterstains Gram-negative bacteria pink. * Result: Gram-positive purple, Gram-negative pink/red. 10. Penicillin Penicillin prevents the formation of cross-links in bacterial peptidoglycan. This: * Weakens the bacterial cell wall. * Allows water to enter by osmosis. * Causes the bacterial cell to burst (lysis). Gram-positive bacteria are generally more susceptible because their peptidoglycan is more accessible. Gram-negative bacteria have an outer membrane that can prevent or reduce penicillin entry. PART 3 – B2: SPECIALISED CELLS 11. Palisade cells Adaptations: * Contain many chloroplasts for photosynthesis. * Tall, thin shape allows cells to be closely packed. * Found near the upper surface of leaves to receive light. * Large vacuole pushes chloroplasts towards the cell edge. * Thin cell wall helps carbon dioxide diffuse into the cell. 12. Sperm cells Mnemonic: A Happy Mouse Tails * A = Acrosome: Contains enzymes to digest the egg’s outer layers. * H = Haploid nucleus: Contains half the normal chromosome number. * M = Mitochondria: Produce ATP for movement. * T = Tail: Flagellum propels the sperm. * S = Streamlined: Helps movement through fluid. 13. Egg cells Adaptations: * Large cytoplasm containing nutrient reserves. * Haploid nucleus. * Zona pellucida surrounds the egg. * Cortical granules help prevent polyspermy after fertilisation. Polyspermy: When more than one sperm fertilises an egg. 14. Root hair cells Adaptations: * Long extension gives a large surface area. * Thin cell wall gives a short diffusion distance. * Cell sap helps water enter by osmosis. * Mitochondria supply ATP for active transport of mineral ions. 15. Red blood cells Adaptations: * Biconcave shape gives a large surface area. * No nucleus, leaving more room for haemoglobin. * Haemoglobin binds oxygen. * Flexible shape allows movement through narrow capillaries. * Thin centre gives a short diffusion distance. Oxygen + haemoglobin ⇌ oxyhaemoglobin. 16. White blood cells Two important types: Neutrophils * Have a lobed nucleus. * Engulf pathogens by phagocytosis. * Use lysosomes containing digestive enzymes. * Form part of the innate immune response. * Respond rapidly to infection. Lymphocytes * Have a large, round nucleus. * B lymphocytes can develop into plasma cells. * Plasma cells produce specific antibodies. * Some become memory cells. * T lymphocytes can destroy infected cells. 17. Neutrophils and lymphocytes: similarities and differences Similarities mnemonic: Both Need Protection * Both = Both are white blood cells. * Need = Both contain a nucleus. * Protection = Both protect against pathogens. Differences: Neutrophils Lymphocytes Phagocytosis. Specific immune response. Lobed nucleus. Large, round nucleus. Digest pathogens using lysosomes. B cells produce antibodies. Part of innate immunity. Part of adaptive immunity. Respond rapidly. Can form long-lasting memory cells. 18. Antibodies and immunity Learn: * An antigen is a molecule recognised by the immune system. * Antibodies have binding sites complementary to specific antigens. * Antibodies bind to antigens. * This can neutralise pathogens or help other immune cells destroy them. * B lymphocytes can form memory cells. * Memory cells help produce a faster secondary response. 19. Allergies Mnemonic: A M H * A = Allergen enters the body. * M = Mast cells become involved. * H = Histamine is released. Histamine causes: * Blood vessels to widen. * Capillaries to become more permeable. * Fluid to move into tissues. * Swelling, itching and other allergic symptoms. 20. Transplant rejection Learn this sequence: * Donor cells have antigens. * The recipient recognises these antigens as foreign. * T lymphocytes recognise the foreign cells. * T cells attack the transplanted tissue. * Tissue matching reduces the chance of rejection. * Immunosuppressants reduce immune activity. PART 4 – B3: TISSUES AND THE RESPIRATORY SYSTEM 21. Epithelial tissues Squamous epithelium * Thin, flat cells. * Usually one cell thick in diffusion surfaces. * Short diffusion distance. * Found in alveoli and capillary walls. Columnar epithelium * Tall cells. * Can contain goblet cells. * Ciliated columnar cells move mucus. * Microvilli in the gut increase surface area for absorption. Endothelium * Lines the inside of blood vessels. * Smooth surface reduces friction. * Thin capillary endothelium allows diffusion. 22. COPD COPD stands for chronic obstructive pulmonary disease. Two important conditions: Emphysema Mnemonic: Smoking Makes Every Alveolus Lose Elasticity * Smoking causes inflammation. * White blood cells release elastase. * Elastase destroys alveolar walls. * Alveoli merge into larger air spaces. * Surface area decreases. * Elastic recoil decreases, causing difficulty breathing out. Chronic bronchitis Mnemonic: Irritated Goblets Make Coughing Increase * I = Inflammation of the bronchi. * G = Goblet cells enlarge. * M = More mucus is produced. * C = Cilia become damaged. * I = Infections become more common. * B = Bronchi narrow, causing coughing and breathing difficulties. 23. Alveoli adaptations Mnemonic: Silly Tigers Carry Very Massive Eggs * S = Surface area: Millions of alveoli create a large surface area. * T = Thin walls: One cell thick, short diffusion distance. * C = Capillaries: Dense network maintains the concentration gradient. * V = Ventilation: Refreshes alveolar air. * M = Moisture: Gases dissolve in the lining. * E = Elasticity: Allows stretching and recoil. 24. Gas exchange Oxygen moves: Alveolar air → Alveolar epithelium → Basement membrane → Capillary endothelium → Plasma → Red blood cell → Haemoglobin. Carbon dioxide moves in the opposite direction. Fick’s law Diffusion is faster when: * Surface area is larger. * Diffusion distance is shorter. * Concentration gradient is steeper. 25. Breathing and inhalation Mnemonic: Dancing Rabbits Visit Pretty Amazing Places * D = Diaphragm contracts and flattens. * R = Ribs move upwards and outwards. * V = Thoracic volume increases. * P = Pressure inside lungs decreases. * A = Air moves into the lungs. * P = Pressure equalises as air enters. Exhalation * Diaphragm relaxes and becomes dome-shaped. * External intercostal muscles relax. * Ribs move downwards and inwards. * Thoracic volume decreases. * Pressure inside the lungs increases. * Air moves out. 26. Smoking effects Mnemonic: Cigarettes Make Every Lung Suffer * C = Cilia damaged. * M = More mucus produced. * E = Excess infections. * L = Loss of alveolar walls. * S = Surface area reduced. * S = Smoking reduces lung elasticity. Smoking also damages blood vessel endothelium and increases atherosclerosis risk. PART 5 – ATHEROSCLEROSIS AND CIRCULATION 27. Atherosclerosis High-priority 6-marker Mnemonic: Dirty Money’s Find Pipes Narrowing Today * Dirty = Damage: The endothelium lining the artery becomes damaged. * Money’s = Macrophages: Macrophages enter the artery wall and engulf LDL cholesterol. * Find = Foam cells: Macrophages become foam cells, forming fatty streaks. * Pipes = Plaque: Fatty material builds up and forms a plaque. * Narrowing = Narrowing: The plaque narrows the artery and reduces blood flow. * Today = Thrombus: A blood clot can form and block the artery, potentially causing a heart attack or stroke. Risk factors * Smoking. * High blood pressure. * High LDL cholesterol. * Diabetes. * Age. * Poor diet. PART 6 – MUSCLES 28. Skeletal muscle structure Learn these terms: Structure Function Sarcolemma Muscle fibre cell membrane. Sarcoplasm Muscle fibre cytoplasm. Myofibrils Contain actin and myosin. Sarcomere Contractile unit between Z lines. Actin Thin filament. Myosin Thick filament. Sarcoplasmic reticulum Stores and releases calcium ions. Mitochondria Produce ATP. Skeletal muscle fibres are: * Long and cylindrical. * Multinucleate. * Striated. * Packed with myofibrils. 29. Sarcomere changes Structure During contraction A band Stays the same length. I band Shortens. H zone Shortens. Z lines Move closer together. Sarcomere Shortens. Mnemonic: A stays Always the same; I and H get Hit. 30. Sliding filament theory High-priority 6-marker Mnemonic: Clever Tigers Make Powerful Animals Run * Clever = Calcium: Calcium is released from the sarcoplasmic reticulum. * Tigers = Troponin: Calcium binds to troponin, moving tropomyosin. * Make = Myosin: Myosin binds to actin, forming cross-bridges. * Powerful = Power stroke: Myosin pulls actin towards the centre of the sarcomere. * Animals = ATP: ATP binds to myosin, causing detachment. * Run = Reset: ATP is broken down, re-cocking the myosin head. Remember: Actin and myosin do not shorten; they slide past one another. 31. Slow-twitch and fast-twitch fibres Mnemonic: Slow Red Runners Have Endurance Slow-twitch Type I * Red. * Lots of myoglobin. * Many mitochondria. * Dense capillary supply. * Mainly aerobic respiration. * Resist fatigue. * Used for endurance activities such as marathons. Fast-twitch Type II * Paler. * Less myoglobin. * Fewer mitochondria. * Lower capillary density. * More reliance on anaerobic energy pathways. * Contract quickly and powerfully. * Fatigue more quickly. * Used for sprinting and weightlifting. Remember: Slow = Stamina. Fast = Force. PART 7 – NERVOUS SYSTEM 32. Motor neurone structure Mnemonic: Dogs Can Always Nip Toes * D = Dendrites receive signals. * C = Cell body contains nucleus. * A = Axon carries the impulse. * N = Nodes of Ranvier are gaps in myelin. * T = Terminals release neurotransmitters. Myelin sheath * Insulates the axon. * Increases conduction speed. * Schwann cells produce myelin in the peripheral nervous system. * Nodes of Ranvier allow saltatory conduction. 33. Resting potential Mnemonic: Three Naughty Cats Keep Purring Inside * Three = 3 sodium ions pumped out. * Naughty = 2 potassium ions pumped in. * Cats = Pump uses ATP. * Keep = Potassium ions leak out. * Purring = Negative proteins remain inside. * Inside = Inside becomes approximately −70 mV. 34. Action potential Mnemonic: Silly Dogs Run Happily Past Houses * S = Stimulus reaches threshold (−55 mV). * D = Depolarisation begins as sodium channels open. * R = Rising potential as sodium enters. * H = High positive potential, around +40 mV. * P = Potassium channels open and potassium leaves. * H = Hyperpolarisation before returning to resting potential. Important extra facts * Action potentials are all-or-nothing. * A stronger stimulus increases frequency, not the size of the action potential. * The refractory period prevents immediate re-firing. * It helps ensure impulses travel in one direction. 35. Myelinated and non-myelinated neurones Mnemonic: Myelin Jumps Fast * Myelinated neurones have a myelin sheath. * They have nodes of Ranvier. * Impulses jump from node to node. * This is called saltatory conduction. * Non-myelinated neurones conduct continuously. * Myelinated neurones are faster and generally use less energy for impulse transmission. 36. Synaptic transmission High-priority 6-marker Mnemonic: All Clever Vikings Drink Really Slowly * All = Action potential: Arrives at the presynaptic knob. * Clever = Calcium: Calcium channels open and calcium enters. * Vikings = Vesicles: Vesicles release neurotransmitter by exocytosis. * Drink = Diffusion: Neurotransmitter diffuses across the synaptic cleft. * Really = Receptors: Neurotransmitter binds to postsynaptic receptors. * Slowly = Sodium: Sodium channels open and sodium enters, causing depolarisation. Extra: * Neurotransmitter is removed by enzymes or reuptake. * Synapses are one-way because receptors are on the postsynaptic membrane. 37. Acetylcholine Mnemonic: Release, Bind, Sodium, Enzyme, Recycle * Release: Acetylcholine is released from vesicles. * Bind: It binds to postsynaptic receptors. * Sodium: Sodium channels open. * Depolarisation: The membrane becomes less negative. * Enzyme: Acetylcholinesterase breaks down acetylcholine. * Recycle: Choline is taken back into the presynaptic neurone. 38. Agonists and antagonists Mnemonic: Agonist Activates; Antagonist Blocks. * Agonist binds to a receptor and activates it. * It can mimic a natural neurotransmitter. * Antagonist binds without activating the receptor. * It blocks the natural neurotransmitter from binding. Examples: * Nicotine: agonist at certain acetylcholine receptors. * Curare: antagonist at acetylcholine receptors. Other examples to know: * L-dopa is converted into dopamine. * SSRIs block serotonin reuptake. * Botulinum toxin prevents acetylcholine release. * Organophosphates inhibit acetylcholinesterase. 39. Neurotransmitters Neurotransmitter Main role Acetylcholine Muscle contraction and signalling. Glutamate Main excitatory neurotransmitter in the brain. GABA Main inhibitory neurotransmitter in the brain. Dopamine Movement and reward. Serotonin Mood, sleep and appetite. Noradrenaline Alertness and attention. 40. Parkinson’s disease Mnemonic: Dying Dopamine Makes Movement Slow * Dopamine-producing neurones in the substantia nigra degenerate. * Less dopamine is released. * Movement control is disrupted. * Symptoms include tremors, rigidity and slow movement. * L-dopa can be converted into dopamine in the brain. * Dopamine agonists can also help manage symptoms. 41. Depression and SSRIs Mnemonic: Serotonin Reuptake is Controlled, Levels Last * Serotonin is involved in mood regulation. * Serotonin is released into the synaptic cleft. * Normally, some serotonin is taken back into the presynaptic neurone. * SSRIs block serotonin reuptake transporters. * Serotonin remains in the synaptic cleft longer. * It can continue binding to postsynaptic receptors. PART 8 – ECGs 42. ECG waves Mnemonic: Please Quit Rushing, Stay Tranquil * P wave: Atrial depolarisation. * QRS complex: Ventricular depolarisation. * T wave: Ventricular repolarisation. Remember: * Atrial depolarisation is followed by atrial contraction. * Ventricular depolarisation is followed by ventricular contraction. * Ventricular repolarisation is followed by ventricular relaxation. 43. Heart rate calculations \text{Heart rate}=\frac{60}{\text{R-R interval in seconds}} Example: If the R-R interval is 0.8 seconds: 60\div0.8=75\text{ bpm} Know: * Tachycardia: over 100 beats per minute. * Bradycardia: under 60 beats per minute. * Regular R-R intervals indicate a regular rhythm. PART 9 – ALL THE 6-MARK QUESTIONS TO PRACTISE These are the extended-answer questions I would use to test your knowledge. They are based on your notes, not guaranteed predictions. Your 30-question exam checklist Tick each question once you can answer it without notes. 0/30 All 1. B1 – CellsCompare prokaryotic and eukaryotic cells. (6 marks) 2. B1 – CellsCompare light and electron microscopes. (6 marks) 3. B1 – MicroscopyExplain how to calculate magnification and actual size. (6 marks) 4. B1 – Gram stainingDescribe how Gram staining is carried out and how it identifies bacteria. (6 marks) 5. B1 – AntibioticsExplain why penicillin is generally more effective against Gram-positive bacteria. (6 marks) 6. B2 – Specialised cellsExplain how a sperm cell is adapted for fertilisation. (6 marks) 7. B2 – Specialised cellsExplain how a red blood cell is adapted to transport oxygen. (6 marks) 8. B2 – ImmunityExplain how phagocytes destroy pathogens. (6 marks) 9. B2 – ImmunityExplain how lymphocytes defend the body against pathogens. (6 marks) 10. B2 – ImmunityCompare the similarities and differences between neutrophils and lymphocytes. (6 marks) 11. B2 – ImmunityExplain how allergies occur. (6 marks) 12. B2 – ImmunityExplain how organ transplants can be rejected. (6 marks) 13. B3 – TissuesExplain how atherosclerosis develops. (6 marks) 14. B3 – LungsExplain how emphysema affects gas exchange. (6 marks) 15. B3 – LungsExplain how chronic bronchitis develops. (6 marks) 16. B3 – LungsExplain how alveoli are adapted for gas exchange. (6 marks) 17. B3 – LungsExplain the mechanism of inhalation. (6 marks) 18. B3 – LungsExplain how smoking damages the respiratory system. (6 marks) 19. MusclesExplain the sliding filament mechanism of muscle contraction. (6 marks) 20. MusclesCompare slow-twitch and fast-twitch muscle fibres. (6 marks) 21. NervesExplain how resting potential is maintained. (6 marks) 22. NervesExplain how an action potential is generated. (6 marks) 23. NervesCompare myelinated and non-myelinated neurones. (6 marks) 24. NervesExplain how an impulse travels along a myelinated neurone. (6 marks) 25. NervesExplain how a synapse transmits a nerve impulse. (6 marks) 26. NervesExplain how acetylcholine works at a synapse. (6 marks) 27. NervesExplain the difference between agonists and antagonists. (6 marks) 28. NervesExplain how Parkinson’s disease affects the nervous system. (6 marks) 29. NervesExplain how SSRIs affect synaptic transmission. (6 marks) 30. ECGsExplain what the P wave, QRS complex and T wave represent. (6 marks) Reset checklist PART 10 – IMPORTANT DEFINITIONS TO MEMORISE Term Meaning Diffusion Net movement of particles from high to low concentration. Osmosis Net movement of water across a partially permeable membrane from higher to lower water potential. Active transport Movement against a concentration gradient using energy. Phagocytosis Engulfing and digesting pathogens. Antigen Molecule recognised by the immune system. Antibody Protein that binds to a specific antigen. Depolarisation Membrane potential becomes less negative. Repolarisation Membrane potential returns towards its resting value. Hyperpolarisation Membrane potential becomes more negative than resting potential. Synapse Junction between neurones where signals are transmitted. Neurotransmitter Chemical messenger released at a synapse. Exocytosis Release of substances when vesicles fuse with a cell membrane. Atheroma Fatty plaque in an artery wall. Thrombus Blood clot formed within a blood vessel. Sarcomere Contractile unit of a myofibril. Oxyhaemoglobin Haemoglobin bound to oxygen. COPD Chronic obstructive pulmonary disease. Differentiation Process by which cells become specialised. PART 11 – THE MOST IMPORTANT MNEMONICS TO KNOW Here is your quick podcast-style recap. Read these aloud every day. Topic Mnemonic Cell organisation Cats Take Over Sofas Prokaryotic structures Naughty Pigs Rarely Chase Wolves Graticule calibration Lazy Chefs Dice Meat Gram staining Hot Cats In Autumn Spring Sperm cell A Happy Mouse Tails Atherosclerosis Dirty Money’s Find Pipes Narrowing Today Neutrophil and lymphocyte similarities Both Need Protection Alveoli Silly Tigers Carry Very Massive Eggs Inhalation Dancing Rabbits Visit Pretty Amazing Places Chronic bronchitis Irritated Goblets Make Coughing Increase Emphysema Smoking Makes Every Alveolus Lose Elasticity Sliding filament Clever Tigers Make Powerful Animals Run Slow-twitch fibres Slow Red Runners Have Endurance Motor neurone Dogs Can Always Nip Toes Action potential Silly Dogs Run Happily Past Houses Resting potential Three Naughty Cats Keep Purring Inside Synapse All Clever Vikings Drink Really Slowly Parkinson’s Dying Dopamine Makes Movement Slow ECG Please Quit Rushing, Stay Tranquil PART 12 – HOW TO REVISE THIS FOR YOUR EXAM I would revise in this order: Your 7-day revision plan * Day 1 – Cells Cell structures, prokaryotes, eukaryotes, microscopes and magnification. * Day 2 – Specialised cells Sperm, egg, root hair, palisade and red blood cells. * Day 3 – Immunity Neutrophils, lymphocytes, antibodies, allergies and transplant rejection. * Day 4 – Lungs and circulation Alveoli, inhalation, COPD, smoking and atherosclerosis. * Day 5 – Muscles Sarcomeres, sliding filament theory and muscle fibre comparisons. * Day 6 – Nervous system Resting potential, action potentials, synapses, neurotransmitters and Parkinson’s. * Day 7 – Exam practice Attempt the 6-mark questions without notes, then check your answers. My final advice For every 6-marker, learn: * The mnemonic. * What every letter stands for. * The scientific explanation. * The correct order of events. You have already shown that you can remember the atherosclerosis sequence and explain it in your own words. That’s exactly how you should practise the rest. Don’t just memorise the mnemonics. Make sure you understand what each biological process actually means. That’s what will help you answer the question even if the examiner words it differently.

Lecture 14: Visual Cortex, Streams, and Perceptual Disorders

Chapter 6: Dorsal and Ventral Streams

Week 6 : TV & Streaming

Grade 10 Hospitality Studies — Exam memo Section A: Short questions (40 marks) Question 1.1 — Multiple choice Question Answer 1.1.1 B — Pancake 1.1.2 A — Too much baking powder was used 1.1.3 A — Glaze 1.1.4 C — Marinade 1.1.5 D — Tortellini 1.1.6 C — 250 ml (likely expected answer) 1.1.7 C — Purchasing the same amount of ingredients 1.1.8 B — Earl Grey 1.1.9 C — Déglacé 1.1.10 B — Maître d'hôtel Question 1.2.1 — Cheese matching Write only the letter next to each number. Question Answer 1.2.1.1 Very hard cheese B — Pecorino 1.2.1.2 Soft, ripened cheese D — Brie 1.2.1.3 Semi-hard cheese G — Emmental 1.2.1.4 Processed cheese E — Sliced cheese 1.2.1.5 Special cheese C — Feta Question 1.2.2 — Pasta matching Question Answer 1.2.2.1 Italienne D — Pasta with butter and grated cheese 1.2.2.2 Napolitaine E — Tomato sauce and Parmesan 1.2.2.3 Cannelloni B — Filled pasta tubes with béchamel sauce and cheese 1.2.2.4 Lasagne A — Layers of pasta, mince and béchamel sauce with cheese 1.2.2.5 Milanese C — Tomato sauce, ham and cheese Question 1.3 — Culinary terminology Question Answer 1.3.1 Mirepoix — a mixture of carrots, celery and onions used to flavour stocks and sauces. 1.3.2 Sifting — passing dry ingredients through a sieve. 1.3.3 Grating — rubbing food against a grater. 1.3.4 Skimming — removing fat from the surface of a liquid. 1.3.5 Dusting — sprinkling icing sugar or castor sugar over a cake. 1.3.6 Mageu (mahewu) — fermented maize-meal drink or sour porridge. 1.3.7 Crêpe — a thin French pancake used to wrap fillings. 1.3.8 Durum wheat — the wheat commonly used to make dried pasta. 1.3.9 Approximately 1 kg of cooked pasta. 1.3.10 Fruit purée / coulis — fruit that has been puréed, with or without sugar. Question 1.4 — Choose the correct answers 1.4.1 Combination heat cooking methods A — Braising C — Pot roasting The question asks for three, but these are the two clear combination methods in the options shown. Check this question against your class notes because the paper may contain an error. 1.4.2 Types of cooking equipment The options shown are all examples of cooking equipment: A — Bain-Marie B — Combi oven C — Steamer D — Convection oven E — Bratt pan The instruction says to choose three, so I can't confidently identify the intended three from this list alone. 1.4.3 Types of coffee A — Espresso B — Cappuccino D — Mocha Latte E — Café Mocha Rooibos is not coffee. Section B: Kitchen and restaurant operations, hygiene, safety and security (40 marks) Question 2.1 — Burns and first aid 2.1.1 Give one reason why Lungelo could have burnt herself with the wet cloth. (2) Water in the wet cloth can heat up and produce steam, which can burn the skin. The wet cloth transfers heat more readily than a dry insulating cloth. 2.1.2 Classify the type of burn. (1) - A thermal burn, caused by heat. 2.1.3 Explain how to treat her burn. (3) Cool the burn under cool running water for 20 minutes. Remove jewellery or clothing near the burn if it is not stuck to the skin. Cover it loosely with a sterile, non-fluffy dressing. Do not apply ice, butter or toothpaste. 2.1.4 Provide the aim of first aid. (2) Preserve life. Prevent the condition from worsening and promote recovery. 2.1.5 Distinguish between a chemical and an electrical burn. (2) Chemical burn: Caused by corrosive chemicals damaging the skin or tissues. Electrical burn: Caused by an electric current passing through the body. Question 2.2.1 — Preparation apparatus (6) A — Colander Use: To drain water from cooked pasta or rinse fruit and vegetables. B — Palette knife Use: To spread icing or lift and turn delicate foods. C — Spatulas / scrapers Use: To scrape mixtures from bowls or fold ingredients together. Question 2.3 — Franchises 2.3.1 Three advantages and three disadvantages (6) Advantages Disadvantages An established brand attracts customers. Franchise fees and royalties must be paid. Training and support are provided. The owner has limited independence. An established business model reduces some risks. Strict rules limit changes to products and operations. 2.3.2 Identify three franchises. (3) McDonald's KFC Nando's Question 2.4 — Three types of formal accommodation (3) Hotels Motels Guest houses Question 2.5 — Why must departments work closely together? (4) To ensure efficient communication and coordination. To prevent mistakes and delays. To provide good customer service. To ensure all departments work towards the same goals. Question 2.6 — Parts of a chef's uniform 2.6.1 Chef's jacket (3) Protects the skin from heat and minor splashes. Helps maintain a professional appearance. Can be removed or changed when dirty to maintain hygiene. 2.6.2 Safety shoes (2) Protect the feet from hot liquids, falling objects and sharp items. Provide grip to reduce slipping on wet or greasy floors. Question 2.7 — Three basic methods of pest control (3) Physical or mechanical control — traps, screens and sealing entry points. Chemical control — approved pesticides. Biological control — using natural enemies of pests. Section C: Nutrition, menu planning and food commodities Your screenshots don't show every page of Question 3 clearly. I can answer the visible questions from Question 4 on page 10. Question 4.3 — Salt water test 4.3.1 Evaluate the freshness of the egg and motivate your answer. (2) The egg appears to be standing upright at the bottom of the glass, so it is likely older rather than very fresh. As eggs age, the air cell grows and the egg becomes more buoyant. A fresh egg generally sinks and lies flat. An older egg may stand upright. An egg that floats is generally very old and should be checked carefully before use. Question 4.4 — Guidelines for purchasing eggs (4) Choose clean eggs with uncracked shells. Avoid eggs with unpleasant odours. Buy eggs from a reputable supplier. Check the expiry or best-before date and ensure they have been stored appropriately. Question 4.5 — Three ways to store eggs (3) Store in a refrigerator at a consistent, cool temperature. Keep in their carton to protect them and reduce absorption of odours. Store away from strong-smelling foods and use older eggs first. Question 4.6.1 — Properties of a French omelette (3) Pale golden or lightly coloured on the outside. Soft, moist and tender inside. Neatly folded, with no burnt patches. Question 4.7 — Difference between butter and margarine (2) Butter: Made from milk fat or cream. Margarine: Made mainly from vegetable oils or other permitted fats. Question 4.8 — Two bacteria used in yoghurt manufacture (2) Lactobacillus delbrueckii subsp. bulgaricus Streptococcus thermophilus Question 4.9 — Three heat-treatment methods applied to dairy products (3) Pasteurisation Sterilisation Ultra-high-temperature (UHT) treatment Question 4.10 — Four milk substitutes (4) Soya milk Oat milk Almond milk Rice milk Question 4.11 — Correct way to freeze mince (3) Divide the mince into meal-sized portions. Place in airtight, freezer-safe packaging and flatten into thin portions. Label with the date and freeze promptly at −18 ∘ C or colder. Question 4.12 — Two cooking methods for minced meat (2) Frying Stewing Question 4.13 — How to correctly pour tea (3) Place a tea strainer over the cup if using loose-leaf tea. Pour the brewed tea carefully into the cup without spilling. Serve with milk, sugar or lemon according to the customer's preference.

Stream Bio Unit 2

Exam 2 Bus. Spread. Modeling

Water and Stream Test Unit 2 Environmental

Airborn pathogens, disease spread

29. An introduction to A Level organic chemistry Formulas, Fn groups, Naming Functional groups and formulae Functional group: atom/group of atoms in an organic molecule that determines its characteristic chemical and physical properties Arenes: aromatic compounds that contain a benzene ring chemical properties Compound can undergo Electrophilic attack: is e- rich due to π system of delocalised e- Resistant to addition reactions: delocalised e- ring system makes benzene stable physical properties b.p 80 C: Benzene has id-id forces of attraction between the molecules Insoluble in water: non-polar hydrocarbons in arene (not energetically favourable for benzene to break many H bonds between water molecules to be soluble) Halogenoarenes: aromatic compounds containing halogen bonded to benzene ring chemical properties Prone to Electrophilic attack can take part in substitution reactions physical properties Chloro, broom, iodo benzene liquid at r.t with oily texture b.p. Increases down group: larger halogen = more e- = stronger id-id forces = more energy to separate insoluble in water: non-polar hydrocarbon ring Phenols: aromatic compounds containing a hydroxide bonded to benzene ring chemical properties acidic: O in -OH donates a lone pair into ring (more acidic than alcohols) = increased e- density in ring = more reactive = easier for H to be donated react with reactive metals (e.g. Na) to form phenoloxide ions and H gas physical properties White, crystallline solid disinfectant-like smell soluble in water: can form H bonds with water due to -OH group Acyl chlorides: carboxylic acid derivatives containing a chlorine atom, and an acyl group attached to C=O chemical properties colourless extremely reactive and readily takes part in substitution (Cl substituted ) fuming liquids with strong smell: react with water vapor in air Physical properties react violently with water (cannot determine its solubility with water ) Amines: compounds with -NH2 (primary), -NH (2 °) , or -N (3 ° ) amine group chemical properties basic compounds: due to lone pair of e- on nitrogen physical properties lone pair on N can form H bonds soluble in water: form H bond with water solubility ↓ as nonpolar hydrocarbon chain gets longer / molecule gets bigger fishy smell Amides: compounds containing amine group (-NH2) carbonyl group (C=O) amide group -CONH2 chemical properties less basic than amides: lone pair of e- on N is delocalised physical properties soluble in water: form H bonds with water solubility ↓ as nonpolar hydrocarbon chain gets longer / molecule gets bigger Amino Acids: building blocks of proteins, consisting amine group (-NH2) and carboxylic group (-COOH) chemical properties react with bases to form salts react with alcohols to form esters react with amines to form amides physical properties most are soluble in water but insoluble in organic solvents most have chiral centres, exhibit optical isomers Formulae of Organic Compounds Nomenclature of Compounds Naming organic compounds Identify longest C chain containing the functional group Identify fn group on the chain to determine the suffix or prefix on the compound Count along the carbon chain such that the functional group has the lowest number Add any side chains or lower priority functional groups as prefixes to the beginning of the name in alphabetic order Use the prefixes di-, tri- and tetra- if there are two or more identical functional groups or side chains Characteristic organic reactions Electrophilic substitution Electrophile: e- loving species they are e- deficient and acts as e- pair acceptor Substitution reactions: reactions replacing 1 atom / group by another Electrophilic substitution: group / atom replaced by an electrophile e.g. bromine electrophile attacks e- - rich benzene ring Addition-elimination (nucleophilic) nucleophilic addition of small molecule followed by elimination of small molecule includes hydrolysis reaction of alcohols to form esters reaction with ammonia and 1° amines to form amides e.g. Hydrolysis of acyl chlorides Hydrolysis - acyl chloride to carboxylic acid water molecule adds across C=O bond HCL eliminated Ester formation - acyl chlorides + alcohol Alcohol adds across the C=O bond HCl molecule is eliminated Amide formation - acyl chloride + 1° amines + conc ammonia amine or ammonia adds across C=O bond (lone pair on N attacks carbonyl C atom in acyl chloride) HCl eliminated Shapes of aromatic organic molecules Aromatic molecules consist of one or more rings with conjugated π systems Conjugated π systems arise from alternating double and single bonds in which the electrons are delocalised Shape of benzene and aromatic compounds - why are they more stable? Benzene and other aromatic compounds are planar and regular because each carbon atom is sp² hybridised. Each C forms three σ bonds in a trigonal planar arrangement with bond angles of 120°. The remaining unhybridised p orbital on each carbon overlaps sideways with neighbouring p orbitals to form a continuous, delocalised π system above and below the ring. Because the π electrons are delocalised over the whole ring, all the C–C bonds are identical and have intermediate character between a single and double bond. This is why benzene is unusually stable. Why are benzene more stable? delocalised π electrons above and below the ring Optical isomerism, Chirality and drug production Stereoisomers: same structural formula, diff arrangement in space (geometrical, optical) Optical 4 diff groups of / atoms central chiral carbon chiral molecules exist as 2 optical isomers / enantiomers non-superimposable mirror images same physical / chemical properties rotate in opposite directions in plane polarised light (1 clockwise 1 anticlockwise ) Similarities of enantiomers differences in enantiomers same physical and chemical properties differ from ability to rotate plane polarised light and biological activity nonsuperimposable mirror images Biological activity of enzymes enzymes are chiral proteins, bond to specific active site for biological response mirror image of enantiomer will not bind to same active site as it is not the same shape, no biological response Optical activity and Racemic mixtures reaction mixture is optically active if there is an uneven mixture of each enantiomer (e.g. 20% rotates clockwise, 80% rotates anticlockwise, net effect is plane of polarised light rotates anticlockwise) racemic mixture: equal amounts of enantiomers present in soln optically inactive as enantiomers cancel out each others effect, plane polarised light not changed the rotation of plane polarised light can be used to determine the identity of an optical isomer e.g. pass plane polarised light through a sample containing one of the two optical isomers of a single substance Depending on which isomer sample contains, the plane polarised light will be rotated clockwise / anti-clockwise clockwise rotation: R enantiomer anticlockwise rotation: S enantiomer No effect will be observed when the sample is a racemic mixture Chirality and Drug production most drugs to treat disease have 1+ chiral centres and can ∴exist as enantiomers diff in biological activity in enantiomers means difference in effectiveness as medicine drugs should be prepared so that only 1 optical isomer produced, to ↑ effectiveness Potential different biological activity of enantiomers e.g. drug naproxen treats pain from arthritis 1 enantiomer eases pain 1 enantiomer causes liver damage separate racemic mixture into 2 pure enantiomers due to difference in biological activities reduce side effects ↓ dosage by half, reduces production cost chiral catalysts to produce 1 pure optical isomer only small amount chiral catalysis needed + reused e.g. enzyme 30. Hydrocarbons - Arenes Reactions of arenes substitution halogenation nitration Friedel-Craft's alkylation Friedel-Craft's acylation other reaction Complete Oxidation Hydrogenation Electrophilic substitution electrophile: e- pair acceptor, attracted to delocalised e- substitution: 1+ H replaced by a fn group generating electrophile+ using catalyst Electrophilic attack on benzene ring (electrophile accepts 2 π e- , +ve charge remains) regenerating aromaticity by heterolytically cleavage of C-H bond (bonding pair foes into benzene π system) Addition reactions of arenes arenes undergo substitution due to delocalisation of e-, aromaticity restored by heterolytic cleavage of C-H bond in addition, aromaticity / stability not restored (e.g. hydrogenation), Hydrogenation of benzene is less exothermic than expected for three isolated C=C bonds, because the aromatic stabilisation of benzene is lost Halogenation (in the aromatic ring) reactants: Cl2 / Br2 (Cl+ / Br+ electrophile) , arene conditions: rt and pressure catalyst: anhydrous AlCl3 / AlBr3 (catalyst needed due to stability of benzene structure) formation: AlCl3 + Cl2 ⇒ AlCl4- + Cl+ reformation: H+ + AlCl4- ⇒ AlCl4 + HCl product: halogenoarenes / aryl halide In halogenation of Alkylarenes, e- donating alkyl group activates positions 2, 4 (as well as OH-, NH2). forms 2 products multiple substitutions when excess halogen used Halogenation (of alkylarenes) in side chain free radical substitution reaction reactants: halogen, boiling alkyl arene conditions: UV light if excess halogen: all H on alkyl side chain will be substitution by X atoms Nitration reactants: conc HNO3 (NO2+ electrophile), arene conditions: 20-60 ° C (higher = more NO2+ substituted) catalyst: conc H2SO4 formation: HNO3 + H2SO4 ⇒ NO2+ + 2HSO4- + H3O+ reformation: H+ + HSO4- ⇒ H2SO4 In nitration of Alkylarenes, e- donating alkyl group activates positions 2, 4 Friedel-Crafts alkylation substitution of alkyl chain reactant: chloroalkane (CH3CH2+ electrophile), arene condition: heat under reflux catalyst: anhydrous AlCl3 formation: AlCl3 + CH3CH2Cl ⇒ CH3CH2+ + AlCl4- reformation: AlCl4- + H+ ⇒ AlCl3 + HCl Friedel-Crafts acylation substitution of an acyl group (group containing carbonyl, C=O ) reactant: acyl chloride (CH3CH2CO+ electrophile) conditions: heat under reflux catalyst: anhydrous AlCl3 formation: AlCl3 + CH3CH2COCl ⇒ CH3CH2C=O+ + AlCl4- reformation: AlCl4- + H+ ⇒ AlCl3 + HCl Complete oxidation of side chains alkyl side-chains in alkyl arenes are oxidised to carboxylic acids when refluxed with alkaline KMnO4 and then acidified with dilute H2SO4 reactants: hot alkaline KMnO4, dilute H2SO4, alkyl arenes conditions: heat under reflux Hydrogenation addition reaction to form cyclohexane reactants: H2 gas conditions: heat (200 ° C at 30 atm ) catalyst: Pt/Ni Directing effects of substituents on arenes substituents: already on arene that direct substitution reactions to diff. ring positions E- withdrawing groups / substituents e- donating groups / substituents remove e- density from π system in benzene ring deactivating groups (slow attack by e+) directs e+ to positions 3, 5 e.g. COOH, X, NO2 donate e- density into π system of benzene ring activating groups (allow e+ to react faster) directs e+ to positions 2, 4, 6 e.g R, NH2, OH 31. Halogen compounds Halogenoarenes: arenes bonded to X atoms Producing halogenoarenes substitution reactions of arenes with chlorine or bromine in presence of anhydrous AlCl3 catalyst reactants: Cl2 / Br2 (Cl+ / Br+ electrophile) , arene conditions: rt and pressure catalyst: anhydrous AlCl3 / AlBr3 (catalyst needed due to stability of benzene structure) formation: AlCl3 + Cl2 ⇒ AlCl4- + Cl+ reformation: H+ + AlCl4- ⇒ AlCl4 + HCl product: halogenoarenes / aryl halide Substitution of benzene Substitution of methylbenzene substitution of 6 position only occurs in excess chlorine Reactivity of halogenoarenes Why are aryl halides less reactive than haloalkanes? C-H bond in aryl halides is stronger due to the partial overlap of lone pairs on halogen atom with the π system in the benzene ring C-H bond ∴ has a partial double bond character 32. Hydroxy compounds Reactions of alcohols Formation of esters reaction: addition-elimination (esterification) reactants: alcohols/phenols, acyl chlorides nucleophile: OH- (attacks e- deficient carbonyl (COCl) C ) COCl bond breaks, Cl is substituted, HCl fumes formed Why are esters formed from acyl chlorides rather than from C. acids? more effective to form esters from acyl chlorides acyl chlorides are more reactive (produce esters faster) acyl chloride reactions go to completion (more ester formed) Esterification using phenols additional reactants: base (e.g. NaOH) base: deprotonate phenol to form phenoxide ion phenoxide better nucleophile than phenol, attack on carbonyl C occurs more readily Phenol phenol: benzene ring with -OH group attached Production of Phenol From reaction of phenylamine with nitrous acid (HNO3) reactants: NaNO2, dilute acid (to form HNO2), phenylamine conditions: ice (under 10 ° C) step 1 and 2, heat step 3 forming nitrous acid NaNO2 + HCl ⇒ (ice) HNO2 + NaCl forming unstable diazonium salt forming phenol via thermal decomposition (due to instability) reactions of phenol Many reactions due to e- rich benzene ring and polar -OH group with bases with reactive metals with diazonium salts nitration bromination Acid-base reactions Acid-base reaction of phenols with base -OH: slightly acidic (weak acids), act as acid in acid-base reaction dissolve in alkaline soln forming phenoxide salt and water Acid-base reaction of molten phenols with reactive metals forms soluble phenoxide salt and H2 gas Reaction with diazonium ions diazonium ions very reactive due to -N2+ group acid-base reaction conditions: ice for cold diazonium ion added to phenoxide ion Reactions of the aromatic ring phenols react more readily with e+ than benzene due to one lone pair of e- on O in -OH overlaps with π bonding system, ↑ e- density of phenol’s benzene ring and making it more susceptible to electrophilic attack -OH activates ring, directs e+ to 2, 4, 6 positions Nitration of phenols electrophilic substitution reaction reactant: dilute HNO3, phenol when conc HNO3 used, product is 2, 4, 6- trinitrophenol conditions: rt milder conditions as phenol is more reactive Bromination of phenols electrophilic substitution reaction reactants: bromine water, phenol conditions: rt phenol decocolourises orange bromine soln to form 2, 4, 6 - tribromophenol (white ppt) as phenol is more reactive, no need for anhydrous AlBr3 catalyst, can react with bromine water Reactions of other phenolic compounds (contain phenol functional group, e,g, 1-naphthol) -OH group is also e- donating, activates benzene ring to electrophilic substitution reactions, e+ directed to 2, 4 positions (on phenol) C in position 6 shared by both rings, no H atom = no substitution can react in similar way as phenol Acidity of phenols Phenols are weak acids phenols react more readily with e+ than benzene due to one lone pair of e- on O in -OH overlaps with π bonding system, ↑ e- density of phenol’s benzene ring and making it more susceptible to electrophilic attack Phenol’s conjugate base is the phenoxide ion. -ve charge is delocalised over the entire ion as a lone pair on O overlaps with the ring’s delocalised π system, which reduces charge density on oxygen H⁺ ions are ∴ less strongly attracted to phenoxide ion, so phenol is less likely to reform Therefore, phenol is more likely to lose H⁺ and act as an acid Stability of conjugate base phenoxide more stable as -ve charge spread out, so phenol more likely undergo ionisation eqm shifts right, more phenol donate H+ (act as acid) Relative acidities of water, phenol, ethanol smaller pKa = stronger acid order of acidity explained by conjugate bases Delocalisation of charge density phenoxide (conjugate base of phenol): charge density of O is spread out over ion, O less available for bond formation with H+ ethoxide (conjugate base of ethanol): ethyl group is e- donating, donates e- density to O atom, O more available for bond formation with H+ hydroxide (conjugate base of water): charge density of O cannot become delocalised over a ring, OH- more readily accepts H+ than phenoxide no e- donating alkyl groups to O, less -ve O, O less readily accepts H+ compared to ethoxide Overall conjugate base more readily accepts H+ = stronger conjugate base = weaker acid strong acid eqm shifts right favouring dissociated ions and H+ 33. Carboxylic acids and derivatives Benzoic acid: C6H5COOH can be used to synthesize esters Carboxylic acids Production of benzoic acid formation of benzoic acid from Oxidation of alkylbenzenes alkylbenzene heated under reflux with hot alkaline KMnO4, then acidified with dilute acid to protonate carboxylate salt and form benzoic acid reactants: hot alkaline KMnO4 (oxidising agent), dilute acid (e.g. HCl), alkylbenzene purple Mn2+ turns colourless as reduced to Mn4+ brown ppt MnO2 formed conditions: heat under reflux Reactions of Carboxylic acids Reactions of C, acids to form acyl chlorides reactants PCl5 (s) PCl3 (l) + heat SOCl2 (l) Forming carboxylic acids from oxidation of 1 ° alcohols alcohol ⇒ aldehyde ⇒ c. acid Further oxidation of c. acids such as methanoic and ethanedioic acid methanoic acid (strong reducing agent) gets further oxidised to CO2 by warming with mild oxidising agents like Fehling’s or Tollen’s reagent Fehlings: Cu2+ reduced to Cu+, form red ppt Cu2O Tollens: Ag+ reduced to Ag using stronger oxidising agents like acidified KMnO4 or acidified K2Cr2O7 KMnO4: purple soln turns colourless as Mn7+ reduced to Mn2+ K2Cr2O7: orange soln turns green as the Cr6+ reduced to Cr3+ ions Ethanedioic acid gets further oxidised to CO2 Conditions: Strong oxidised agent - warm acidified KMnO4 needed Relative acidities of C. acids, Phenols, and alcohols C acids can lose H+ in aq soln to form carboxylate salts and water Acidities of C. acids longer C chain = weaker acid inductive effect ↑ -ve charge on COO- group More substituted Cl atoms = stronger acid Cl atoms withdraw e- density from the –COOH group, weakening the O–H bond and stabilise carboxylate ion (reducing the -ve charge density on it) The more stable the carboxylate ion, the less likely it is to attract H⁺ and reform the O–H bond Acidities of c. acids, phenols, alcohols acidities explained by strength of O-H bond and stability of conjugate bases of acids Strength of O-H bond carboxylic acids e- in O-H bond drawn towards C-O bond, e- in C-O bond drawn to C=O bond O-H bond weakened due to C=O withdrawing e- density from it for itself easier to act as acid and lose H+ from OH alcohols lack e- withdrawing C=O group, O-H bond not weakened harder to act as acid and lose H+ Stability of conjugate bases carboxylate ion (c base of carboxylic acid) charge density on O spread over ion because charge is delocalised on an electronegative carbonyl O atom O less available for bond formation with H+ to reform -COOH eqm shifts right, C base more stable than carboxylic acid alkoxide ion (c base of alcohol) alkyl is e- donating group, donates e- density to O atom O more available for bond formation with H+ ion to reform OH lack ability to delocalised charge density on ion, c bases less stable than alcohols, weaker acids than c. acid and phenols eqm lies left phenoxide ion (c base of phenol) charge density of O spread out over ion due to delocalisation of e- (stabilises ion) O less available for bond formation with H+ Phenoxide more stable than phenol Phenoxide less stable than carboxylate since delocalisation of charge density is on C atoms, not electrogenative O atoms eqm lies more right than alcohols, more left than c. acids ethanol is weakest e- donating methyl group strengthens O-H bond methyl donates -ve charge to -COO-, more likely to accept H+ Esters - Production Esters: organic compounds with -COO- functions group nice smelling Naming esters alcohol acyl chloride / carboxylic acid e.g. Producing esters from alcohols and carboxylic acids condensation / esterification reaction Producing esters from alcohols and acyl chlorides more effective: acyl chlorides more reactive(faster), and reactions go to completion (no eqm, max yield) Acyl Chlorides Acyl chlorides: compounds with COCl fn group Production of acyl chlorides Carboxylic acid with solid PCl5 liquid PCl3 + heat liquid SOCl2 Reactions of acyl chlorides addition-elimination: addition of small molecule across C=O, followed by elimination of small molecule acyl chlorides under addition-elimination reactions such as hydrolysis to form carboxylic acid Reaction with alcohols and phenols to form esters Reaction with ammonia and amines to form amides General mechanism for addition-elimination reactions addition of nucleophile across C=O bond elimination of a small molecule such as HCl or H20 lone pair on nucleophile carries out initial attack on carbonyl carbon this is followed by the elimination of an HCl molecule Hydrolysis of acyl chlorides forms carboxylic acid and HCl water (nucleophile) adds across C=O bond HCl eliminated Formation of esters from acyl chlorides esterification reaction reactants: alcohol/phenol, acyl chloride conditions: rt reaction with phenol is slower than alcohol, base such as NaOH used to speed up reaction (deprotonates phenol to form phenoxide, better nucleophile to carry out attack) alcohol /phenol (nucleophile) adds across C=O bond, HCl / NaCl eliminated Formation of amides from acyl chlorides condensation reaction: nucleophile adds to C=O, Cl- eliminated, HCl formed reactants: ammonia or 1°/2 ° amines, acyl chloride nucleophile: Nitrogen (has lone pair of e- ) HCl formed is immediately neutralised by a 2nd molecule of ammonia / amine in excess, forming ammonium salt (e.g. NH4Cl, CH3NH3Cl) Relative ease of hydrolysis of aryl chlorides from most readily broken / easily hydrolysed acyl chloride > alkyl chloride > aryl chloride trend explained by strength of C-Cl bond acyl chlorides - hydrolysed at rt R-COCl C bonded to Cl is also bonded to O both Cl and O are very electronegative, pulling e- away from C, leaving it very δ+ C-Cl bond is weakened nucleophilic attack is more rapid alkyl chloride - hydrolysed by refluxing with strong alkali nucleophile R-C-Cl C bonded to Cl attached to 1 electronegative atom (Cl), pulls e- away from C C is not very δ+ (e- deficient) C-Cl bond is stronger than in acyl chlorides aryl chlorides - hydrolysis will not occur C bonded to Cl is part of delocalised π bonding system of benzene ring one lone pair of e- on Cl overlaps with delocalised system C-Cl bond has some double bond character, becoming stronger 34. Nitrogen compounds Primary and secondary amines 1 ° amines: organic compounds with NH2 fn group attached to an alkyl / aryl group 2 ° amines: organic compounds with group attached to a alkyl /aryl groups Naming -amine: after alkyl prefix (e.g. methyl amine) amino- : if another suffix present or branched/complex amines (e.g. amino methane) Production of Amines 1 ° and 2 ° amines prepared form diff reactions 1 ° amines: reaction of haloalkanes with ammonia reduction of nitriles reduction of amides 2 ° amines: reaction of haloalkanes with 1 ° amine Forming 1 ° amines from haloalkanes with ammonia nucleophilic substitution reaction reactants: excess, hot ethanolic ammonia nucleophile: N in ammonia (replaces X) conditions: heat under pressure Forming 1 ° amine from reduction of nitrile reactants: nitrile vapour, H2 gas conditions: LiAlH4 in dry ether (reducing agent), or Ni catalyst Forming 1 ° / 2 ° amines from reduction of amides reactants: LiAlH4 in dry ether (reducing agent) type of amine depends on nature of amide Forming 2 ° amines from haloalkanes with 1 ° amine nucleophilic substitution reaction reactants: 1 ° amine in ethanol nucleophile: N in 1 ° amine (replaces X) conditions: heat under pressure, sealed tube Reactions of Amines Condensation reaction between Acyl chloride and ammonia or amine produces Amides Cl in acyl chlorides is electronegative, draws e- density from carbonyl C C is e- deficient, attacked by nucleophile like N in ammonia and amines C-Cl bond broken, amide formed reaction with amines ⇒ substituted amide reaction with ammonia ⇒ nonsubstituted amide Why is acyl chloride a more effective reactant than carboxylic acids in formation of amides? c acids less reactive than acyl chloride reaction with c acids dosent fo to completion Basicity of aq soln of Amines and ammonia N in ammonia and amines can accept proton H+, can ∴ act as bases in aq soln (when donating lone pair to form dative bonds) Strength of bases strength of amine depends on availability of lone pair of e- on N to form a dative covalent bond with H+ lone pair more readily available to form dative bond = stronger base positive inductive effect ↑ basicity: alkyl groups donate e- density to N, causing lone pair to become more available delocalisation ↓ basicity: aromatic rings cause lone pair to be delocalised into benzene ring, causing lone pair to be less available Phenylamine and Azo compounds Phenylamine: organic compound with benzene ring and amine fn group Production of phenylamine 3 step synthesis, followed by separation / purification Nitration (forming nitrobenzene) reactants: benzene, conc HNO3 catalyst: conc H2SO4 conditions: 25-60 ° C Reduction (forming phenylamine ion) conditions: hot tin (Sn) and conc HCl under reflux Deprotonation (forming phenylamine) reactants: NaOH, phenylamine ion separation/purification phenylamine separated from reaction mixture by steam distillation Reactions of Phenylamine Both benzene ring and NH2 can take part in chemical reactions bromination of phenylamine formation of diazonium salt Bromination of phenylamine to form 2, 4, 6- tribromophenylamine electrophilic substitution reaction electrophile: N, donate e- density into benzene ring, ↑ e- density in benzene ring activates it, more readily attacked by electrophiles reactants: aqueous bromine, phenylamine conditions: rt Formation of diazonium salt (salt containing N2+ group) reactants: nitrous acid/HNO2, HCl, phenylamine HNO2 formed in test tube with NaNO2 and dilute HCl conditions: below 10 ° C diazonium salt forms phenol upon warming with water Azo compounds Azo compounds: organic compounds with R-N=N=R / azo group often used as dyes Diazonium compounds: contain N2+ group Formation of Azo compounds from coupling reaction of benzene diazonium chloride salt with phenol multi-step process forming nitrous acid reactants: NaNO2, HCl conditions: test tube, under 10 °C / ice NaNO2 + HCl ⇒(ice) HNO2 + NaCl Diazotisation reactants: phenylamine, HNO2, dilute HCl conditions: below 10 ° C / ice (prevent thermal decomposition of diazonium ion to phenol, N and HCl) coupling reaction reactants: phenol, diazonium ion (acts as electrophile, sub into benzene ring of phenol) conditions: alkaline conditions (NaOH deprotonates phenol to phenoxide, more reactive to e+) Why are azo compounds very stable? The delocalised e- in π bonding systems extend across both benzene rings and the –N=N– bridge Other days formed from similar route e.g. formation of yellow dye from coupling reaction between benzene diazonium chloride and C6H5N(CH3)2 Amides Amide: organic compounds with CONR2 amide group non-substituted / 1 ° amide: N bonded to 2H atoms substituted / 2 ° amide: 1 or both H replaced by a hydrocarbon group Production of Amides Formation of Amides from acyl chlorides / c. acid with ammonia / amine condensation reaction: nucleophile adds to C=O, Cl- eliminated, HCl formed nucleophile: Nitrogen (has lone pair of e- ) conditions: rt HCl formed is immediately neutralised by a 2nd molecule of ammonia / amine in excess, forming ammonium salt (e.g. NH4Cl, CH3NH3Cl) Reactions of Amides Amide group can undergo reactions Hydrolysis with aqueous alkali or aqueous acid Reduction with LiAlH4 Hydrolysis of amides to form c. acid and ammonia/ 1 ° amine conditions: reflux with aq acid / alkali products differ depending with amide is substituted nonsubstituted ⇒ c. acid + ammonia substituted ⇒ c. acid + 1 ° amine when refluxed in excess acid⇒ ammonium salt formed base⇒ carboxylate ion formed (deprotonation) Reduction of amides to form amine conditions: LiAlH4 reducing agent nonsubstituted amide ⇒ 1 ° amine + H2O substituted amide ⇒ 2 ° amine + H2O Relative basicity of Amides and Amines lone pair of e- more readily available for dative bonding = stronger base more e- =stronger base amides - weaker base e- withdrawing O in C=O causes lone pair on N to delocalise into C=O group, removed e- density from N lone pair on N less readily available for bonding amine - stronger base e- donating alkyl groups ↑ e- density on N lone pair on N more readily available for bonding Amino Acids Amino acids: organic compounds with 2 fn groups basic amino -NH2 group acidic carboxylic acid -COOH group due to presence of basic and acidic group, they are amphoteric (act as acid and base) R group can be acidic, basic, or neutral Acid-base properties of amino acids + formation of Zwitterion amino acids can undergo most reactions of amines and c. acids, including acid-base reactions (amine + acid, C. acid + base) Amino acids can interact intramolecularly to form zwitterion Zwitterion: ion with both +ve (NH3+) and -ve (COO-) charge formed from amino acids in water due to charges, there are strong intermolecular forces of attraction between amino acids this makes amino acids soluble crystalline solids Zwitterions act as buffer soln acid added: pH ↓ COO- accepts H+ to reform COOH, zwitterion becomes +vely charged base added: pH ↑ NH3+ donates H+ to reform NH2, zwitterion becomes -vely charged Isoelectric point: point at which charge = 0 / zwitterion is neutral a pH level unique to each amino acid due to R group Formation of Peptide bonds NH2 group of one amino acid can react with COOH group of another amino acid to form dipeptide condensation reaction: H2O eliminated peptide bond / link formed dipeptides can undergo condensation reaction again to form tripeptide ( 3 amino acids) polypeptide: many amino acids join to form long chain of molecules proteins are polypeptides Electrophoresis Analytical separation technique, separates ions by placing them in an electric field Sample of amino acids placed between 2 oppositely charged electrodes +ve ions move to -ve electrode -ve ions move to +ve electrode Rate of ion movement depends on size of ions (larger = slower) charge of ions (highly charged = quicker) Electropherogram: bands on gel after electrophoresis each band = particular species Amino acids can be separated according to charge and mass they are colourless, sprayed with ninhydrin (brown/purple stain) to show where they have gone to Changes in charge of amino acid due to pH of solution isoelectric point: no overall charge, no movement of zwitterions pH > isoelectric point: -ve charge, move to +ve electrode pH < isoelectric point: +ve charge, move to -ve electrode -ve charged amino acid: NH3+ donated H+, NH2 and COO- left +ve charged amino acid: COO- accepted H+, NH3+ and COOH left 35. Polymerisation Condensation Polymerisation - Forming polymers Forming polymers such as polyesters, polyamides, proteins Formation of polyesters addition polymerisation: monomers with C=C bonds join to form polymers condensation polymerisation: Small molecule is lost when monomers join together to form polyester polyesters have ester links Monomers for polyesters OH on dicarboxylic acid and H of diol expelled as H2O to form polyester diol (2 -OH) + dicarboxylic acid (2 -COOH) 2 hydroxy carboxylic acids (OH and COOH fn group) Formation of polyamides condensation polymerisation polyamides have peptide links Monomers for polyamides H on diamide and OH on dicarboxylic acid / Cl on dichloride expelled as H2O / HCl as polyamide forms diamide (2 -NH2) + dicarboxylic acid diamide + dichloride (2 -COCl) 2 aminocarboxylic acids (OH and COOH fn group) Making proteins/polypeptides from amino acid monomers (aminocarboxylic acid) amine group (-NH2) and carboxyl group (-COOH) of an amino acid polymerise with another amino acid forms peptide links proteins can be broken into its constituent amino acids through hydrolysis You can deduce the repeat units of a condensation polymer by identifying the linking between monomers chain of C: addition polymer ester link: polyester peptide link: polyamide You can identify monomers from small molecule expelled H2O: c acid H: amine Cl: dioyl chloride Predicting type of polymerisation Identifying type of polymerisation by looking at functional groups Addition polymerisation monomer contains C=C bond double bond opens up to add monomers to either side of starting polymer forms polyalkenes co-polymer: 2+ monomers used to make 1 repeating unit Condensation polymerisation makes polyamides and polyesters summary: Identifying type of polymerisation by considering structure of polymer backbone Addition polymerisation no fn groups on polymer backbone, usually chain of C atoms sidechains might branch off from backbone (e.g. benzene rings, nitrile groups (CN), halogens Condensation polymerisation backbone of polyesters contain ester links (-COO-) backbone of polyamides contain peptide links (-CONH-) Degradability of Polymers Polyalkenes and biodegradability polyalkenes are nonpolar and saturated, making them nonbiodegradable and chemically inert instead, they can be melted and recycled for new uses The energy released from burning can be used to generate electricity Burning plastics in oxygen releases carbon dioxide and water (complete combustion) which can contribute to global warming Photodegradation of polymers some polymers are biodegradable due to their ability to breakdown using light C=O groups along polymer chains absorb UV light this weakens C=O areas of polymers and breaks them down into smaller molecules e.g for polyesters and polyamides Disadvantages of photodegradability weaker polymers UV light not available (e.g. in landfills) Biodegrading polyesters and polyamides via hydrolysis polyesters and polyamides can be broken down by hydrolysis (advantage) hydrolysis: breakdown of molecules using water acid hydrolysis: acid catalyst used alkaline hydrolysis: alkaline catalyst used heating with catalyst breaks polymer Hydrolysis of polyamides acid hydrolysis: breaks polymer into di carboxylic acid and ammonium ions alkali hydrolysis breaks polymer into its sodium salts (e.g. dicarboxylic acid salt and diamines) Hydrolysis of polyesters acid hydrolysis: diol + dicarboxylic acid alkali hydro lists: diol + dicarboxylic acid salt 36. Organic synthesis Elucidating organic molecules - fn groups, properties, reactions Fn groups in AS required as well as: Production of fn groups benzoic acids acyl chlorides amides Producing benzoic acid reactants: methylbenzene oxidation: reflux with hot alkaline KMnO4 to form potassium benzoate protonation with dilute HCl to form benzoic acid Producing acyl chlorides reactants: c. acid substitution reaction: -OH replaced by Cl Producing amides condensation reaction reactants: acyl chloride, NH3 (nonsubstituted amide) / methyl amine (substituted amide) conditions: rt Reactions of functional groups Electrophilic substitution reactions of benzene reaction electrophile halogenation X+ nitration NO2+ alkylation R+ acylation RCO+ Hydrogenation of benzene addition reaction Esterification of phenol more efficient with acyl chloride than carboxylic acid Acid-base reactions of phenol phenol + base ⇒ soluble salt + water Nitration of phenol Bromination of phenol Multi-step synthetic routes Aliphatic reactions Aromatic reactions Analysis 37. Analytical techniques Thin- Layer Chromatography (TLC) Separate small samples 2 phases: stationary and mobile phase Stationary phase thin metal sheet coated in Al2O3, or SiO2 solutes adsorb onto surface and travel thru plate Mobile phase flows over stationary phase polar (water or alcohol) or nonpolar (alkanes), any liquid solvent or gas solvent carries components investigated in coloured components: investigated under UV light using ninhydrin Conducting a TLC analysis prep beaker with small amount of solvent on TLC plate, draw baseline in pencil place spot of reference compound on the left, then a spot of sample on right of baseline and air dry reserve allows identification of compounds in sample put TLC plate inside beaker with solvent - make sure pencil line above solvent, place lid to cover beaker as solvent reaches top, remove plate and draw another pencil line where solvent reached (solvent front) to use to calculate Rf Rf values The extent to which components are separated depends on solubility of each component in the mobile phase and interaction between each component and the stationary phase less polar components travel further up ⇒ larger Rf ⇒ more soluble in mobile phase more polar components do not travel far up ⇒ more attracted to polar stationary phase Gas / Liquid chromatography Analysing bases, volatile liquids, solids in vapour form Stationary phase nonpolar, non-volatile liquid applied to the inner walls of a capillary column mobile phase unreactive carrier gas noble, or inert diatomic e.g. He, N2, Ar Retention time: time taken for sample molecule to travel through the column from time inserted to time detected often recorded on chromatogram each peak = a volatile compound in the analysis sample. each peak has its own rt rt compared with data book values to identify unknown molecules longer rt: nonpolar components, attractiveness to nonpolar liquid in stationary phase shorter rt: polar components, interact with carrier gas Relative concentration of each component = area under each peak Area under peak = ½ base x height peaks roughly take shape of Δ % composition of a particular molecule in a mixture Carbon-13 NMR spectroscopy carbon-13 NMR : analytical tool used to analyse samples and determine the structure of substances Each Carbon environment gives a peak solvent used to dissolve samples for 13C-NMR : CDCl3 (solvent peak around 70 ppm) all 13C-NMR spectra measured relative to TMS / tetramethylsilane ( 0 ppm) predict the number of carbon environments refers to a specific c atom and the combination of atoms, bonds, fn groups attached each unique c environment produces a peak in 13C - NMR if there is a line of symmetry through the molecule, they belong to same environment and product a single peak e.g. predict no. peaks in 13C-NMR spectrum of 1,3-dihydroxybenzene 4 environments = 4 peaks predict each carbon’s chemical shift this is the frequency of an atomic nucleus relative to TMS reference compound measured in ppm example- 13C-NMR spectrum for propanone both CH3 groups are in same environment 2 environments = 2 peaks C=O peak over 200 C-H peaks 0-50 Proton (1H) NMR spectroscopy Technique used to determine structure of molecules paired with other techniques like Mass spec Magnetic field strengths of protons in organic compounds measured and recorded on H NMR spectrum all samples measured against reference compound TMS / Tetramethylsilane single sharp peak at 0 ppm Sample peaks plotted as a ‘shift’ away from this reference peak gives rise to ‘chemical shift’ values for protons on the sample compound (measured in ppm) Features of NMR spectrum intensity of peak against chemical shift area under peak: no. protons in particular environment height: intensity / absorption from protons Molecular / chemical environments diff. arrangements of H atoms have diff environments (identical / symmetry = same environment) no. environments = no. diff chemical shifts / peaks e.g. How many different 1H chemical environments occur in 2-methylpropane? 2 1H chemical environments 2 peaks on 1H NMR spectrum Chemical shift values for H molecular environments symmetrical H = same environment 1 ppm → Alkane 2 ppm → Next to C=O 7 ppm → Benzene ring 9–10 ppm → Aldehyde 10–12 ppm → Carboxylic acid Low resolution 1H NMR peaks on a low resolution NMR spectrum refer to the molecular environments of an organic compound High resolution 1H NMR number of peaks a signal splits into = n + 1 n = number of H on adjacent C atom n+1 splitting patterns Common pairs of splitting patterns TMS and deuterated solvents TMS gives sharp peak at 0 on NMR spectrum why is TMS an ideal reference chemical? it is inert and volatile it reduces undesirable chemical reactions with compound analyses it mixes well with most organic compounds Deuterated solvents in 1H NMR CDCl3 used as a solvent, no peak why is a solvent needed for samples in 1H NMR? dissolving samples in solvent help separate molecules and prevent them from interacting what must the solvent do? be a good solvent for organic molecules not contain any H atoms, does not interfere with NMR signals examples of non-deuterated solvents Carbon tetrachloride, CCl4: This solvent does not contain hydrogen, so it does not produce 1H NMR signals. It is suitable for 1H NMR but does not dissolve all molecules well. examples of deuterated solvents Deuterated solvents are often used in 1H NMR because deuterium (²H) is an isotope of H whose nuclei absorb in a different region from protons, so it gives no signal in a ¹H NMR spectrum Deuterochloroform / Chloroform-d, CDCl3: preferred, contains deuterium (2H) instead of H, does not interfere with the H NMR Deuterium oxide / Heavy water, D2O: deuterium atoms exchange reversibly with the H in the -OH and -NH, signals identified in NMR Identifying -OH and -NH signals Protons in -OH (hydroxyl) and -NH (amine) groups give singlet peaks in ¹H NMR but these signals can be tricky: peaks are broad or sometimes fall outside normal chemical shift ranges H in these groups exchanges quickly with protons from water or acids, so only one peak appears Their chemical shift ranges may overlap with other types of protons To identify these groups more clearly, proton exchange with deuterium oxide (D2O) is used: The deuterium atoms in D2O exchange reversibly with the protons in the -OH or -NH groups -OH + D2O ⇌ -OD + HOD -NH-CO- + D2O ⇌ -ND-CO- + HOD Since deuterium does not absorb in the same region as protons in the NMR spectrum, the signal for -OH or -NH disappears after D2O is added This confirms the presence of -OH or -NH groups in the molecule If peak disappears after D2O, it is due to the exchange of a proton from an -OH or -NH group

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