50 MCQs aligned to the FBISE Curriculum 2022-23 + Model Paper Table of Specifications. Short questions and long questions follow the official model paper. Heaviest emphasis on Coordination & Control and Human Physiology (the high-yield domains).
Section B style (SRQ — 3 marks each). The orange MOST IMPORTANT tag marks the highest-yield short Q per chapter. Purple MODEL PAPER means it appeared in the official Model Paper.
Typical labels: X = Bowman's capsule (ultrafiltration of blood — water, salts, glucose, urea pass; cells & proteins retained). Y = Proximal convoluted tubule (selective reabsorption of glucose, amino acids, ~65% Na⁺ and water). Z = Loop of Henle (sets up the medullary osmotic gradient — descending limb reabsorbs water, ascending limb reabsorbs salts).
(i) Urethritis (urethra), cystitis (bladder), pyelonephritis (kidney). (ii) Causative organism: Escherichia coli. (iii) Prevention: drink plenty of water, urinate frequently, maintain perineal hygiene (front-to-back wiping), avoid holding urine, treat with antibiotics if infected.
Ultrafiltration: blood pressure in glomerulus forces water, ions, urea, glucose into Bowman's capsule, blocking cells & large proteins. Selective reabsorption: useful substances (glucose, amino acids, ions, most water) pumped back to peritubular capillaries in PCT, loop, DCT. Tubular secretion: H⁺, K⁺, drugs and toxins actively secreted from blood into tubule for excretion.
Freshwater: hypertonic to surroundings — gains water by osmosis and loses salts → produces large dilute urine, takes salts actively. Marine: hypotonic to surroundings — loses water and gains salts → drinks seawater, excretes salts via gills/glands, produces small concentrated urine. Terrestrial: risk of dehydration → water-impermeable skin, concentrated urine (urea/uric acid), behavioural adaptations.
A surface where gas exchange occurs between organism and environment. Features: (i) large surface area (~70 m² in alveoli), (ii) thin / one cell thick, (iii) moist for gas dissolution, (iv) well-supplied with capillaries to maintain a steep diffusion gradient.
(i) Paralyses cilia → mucus & pathogens accumulate (smoker's cough, chronic bronchitis). (ii) Destroys alveolar walls → emphysema, reducing surface area for gas exchange. (iii) Tar contains carcinogens → lung cancer. Also COPD, increased risk of TB.
Cause: Mycobacterium tuberculosis (airborne droplets). Symptoms: persistent cough > 3 weeks, blood in sputum, fever, night sweats, weight loss, fatigue. Treatment: 6-month DOTS regimen of isoniazid, rifampicin, pyrazinamide, ethambutol; BCG vaccine for prevention.
Produced by liver hepatocytes, stored in gall bladder, acts in the duodenum (small intestine). Role: emulsifies fats (bile salts) into smaller droplets → increases surface area for lipase action; neutralises acidic chyme; aids absorption of fat-soluble vitamins (A, D, E, K).
(a) Amylopsin (pancreatic amylase): starch → maltose. (b) Trypsin: proteins / peptones → smaller peptides & amino acids. (c) Enterokinase (intestinal): inactive trypsinogen → active trypsin.
Duodenum: receives bile (emulsifies fats) and pancreatic juice (trypsin, amylopsin, lipase) → digestion of carbs, proteins, fats. Jejunum: intestinal enzymes (maltase, sucrase, lactase, peptidases) complete digestion; main site of absorption. Ileum: absorbs final products via villi/microvilli — sugars and amino acids into blood; fatty acids/glycerol into lacteals.
A double-walled sac enclosing the heart. Outer fibrous pericardium (tough connective tissue — anchors heart to diaphragm); inner serous pericardium (two layers — parietal lining the fibrous layer, visceral on the heart surface). Between them is the pericardial cavity with serous fluid that reduces friction during heartbeats.
P wave — atrial depolarisation (atria contracting). QRS complex — ventricular depolarisation (ventricles contracting); atrial repolarisation is hidden inside. T wave — ventricular repolarisation (ventricles relaxing).
Vena cavae → right atrium → (tricuspid valve) → right ventricle → (pulmonary semilunar valve) → pulmonary artery → lungs → pulmonary veins → left atrium → (bicuspid/mitral valve) → left ventricle → (aortic semilunar valve) → aorta → body.
Thrombus: a stationary clot formed inside a blood vessel (e.g. coronary thrombosis). Embolus: a clot (or fat/air bubble) that has detached and travels through circulation until it lodges in a smaller vessel (e.g. pulmonary embolism, stroke).
On contraction: I-band shortens, H-zone shortens / disappears, sarcomere length decreases, A-band unchanged (thick filaments don't shorten — they slide). Z-lines move closer together.
(a) Stored in the sarcoplasmic reticulum (SR). (b) On nerve impulse it is released into the sarcoplasm. (c) Ca²⁺ binds troponin → conformational change moves tropomyosin off actin binding sites → myosin heads attach to actin and pull (cross-bridge cycle) → sliding of filaments → contraction.
Components: outer fibrous annulus fibrosus and gel-like inner nucleus pulposus; sandwiched between two vertebral cartilage end-plates. Causes of slip: ageing/degeneration of the annulus; sudden heavy lifting with poor posture; trauma; obesity; weak back muscles.
Action potential → Ca²⁺ released from SR → binds troponin → tropomyosin moves → exposed actin binding sites → myosin heads form cross-bridges, pivot using ATP → thin filaments slide past thick → sarcomere shortens; ATP detaches and re-cocks the head, cycle repeats until Ca²⁺ is pumped back.
(i) Vasoconstriction of cutaneous arterioles — reduces heat loss. (ii) Shivering thermogenesis — rapid muscle contractions generate heat. (iii) Increased thyroxine / non-shivering thermogenesis via brown fat. (iv) Behavioural: clothing, curling up.
Ectotherm: body heat from external sources (reptiles). Endotherm: generates internal metabolic heat (birds, mammals). Poikilotherm: variable body temperature (fish, amphibians). Homeotherm: constant body temperature (mammals). Most endotherms are homeothermic.
Synaptic cleft prevents direct electrical spread, allows unidirectional chemical transmission and integration. Transmission: action potential reaches presynaptic terminal → voltage-gated Ca²⁺ channels open → vesicles release neurotransmitter (e.g. ACh) into cleft → binds receptors on postsynaptic membrane → opens Na⁺ channels → depolarisation → new action potential generated.
(a) Sodium-potassium ATPase (Na⁺/K⁺ pump). (b) 3 Na⁺ pumped out of the neuron and 2 K⁺ pumped in per ATP hydrolysed — maintains resting membrane potential (~ −70 mV).
RMP (−70 mV) maintained by Na⁺/K⁺ pump. Stimulus opens voltage-gated Na⁺ channels → Na⁺ rushes in → depolarisation to +30 mV. Na⁺ channels close, K⁺ channels open → K⁺ flows out → repolarisation, briefly hyperpolarised. Pump restores RMP. Action potential propagates along axon; in myelinated axons it jumps node-to-node (saltatory conduction).
Synapse = presynaptic terminal + synaptic cleft (~20 nm) + postsynaptic membrane. Presynaptic terminal contains vesicles of neurotransmitter and mitochondria. Excitatory: ACh, glutamate, noradrenaline. Inhibitory: GABA, glycine.
Thyroxine (T4) & triiodothyronine (T3) — raise BMR, growth and development. Calcitonin — lowers blood Ca²⁺ by depositing it in bone. Disorders: hypothyroidism — cretinism (children), myxoedema (adults), goitre (iodine deficiency). Hyperthyroidism — Graves' disease, exophthalmic goitre.
FSH (Follicle-Stimulating Hormone) — stimulates follicle growth and oestrogen secretion in ovaries; spermatogenesis in testes. LH (Luteinising Hormone) — triggers ovulation and corpus luteum formation; testosterone secretion by Leydig cells.
Negative feedback (blood glucose): ↑ glucose → β-cells release insulin → cells take up glucose, liver makes glycogen → glucose drops. ↓ glucose → α-cells release glucagon → glycogenolysis → glucose rises. Positive feedback (oxytocin in childbirth): uterine stretching → hypothalamus → posterior pituitary releases oxytocin → stronger contractions → more stretch → more oxytocin → cycle continues until delivery.
Meissner's corpuscles — light touch (in dermal papillae, fingertips). Pacinian corpuscles — deep pressure and vibration. Ruffini endings — sustained pressure and skin stretch. (Also Merkel discs — fine touch; free nerve endings — pain & temperature.)
Addiction: psychological/physical compulsion to keep using a drug despite harm (withdrawal symptoms if stopped). Tolerance: body adapts so the same dose has less effect — user needs more. Caffeine: tolerance to adenosine receptor antagonism. Nicotine: tolerance via receptor up-regulation; intense addiction via dopamine reward pathway.
Cause: progressive death of brain neurons; accumulation of β-amyloid plaques and tau neurofibrillary tangles; ↓ acetylcholine. Symptoms: memory loss, confusion, mood swings, personality change, eventual loss of bodily function. Treatment: cholinesterase inhibitors (donepezil), memantine; supportive care; no cure.
Interferons are signalling glycoproteins (cytokines) released by virus-infected cells. They bind receptors on neighbouring cells, triggering synthesis of antiviral proteins that degrade viral mRNA and block viral protein synthesis, limiting viral spread.
Reduced phagocytosis weakens the non-specific 2nd line — pathogens are not engulfed/destroyed and inflammation/fever response is impaired. Loss of antigen presentation by macrophages to T-helper cells cripples the specific immune response — fewer activated B-cells & cytotoxic T-cells, so antibody production and cell-mediated immunity both decline.
Antigen binds B-cell receptor → with helper-T-cell assistance B-cell is activated → proliferates into a clone. Most become plasma cells secreting large quantities of antibodies specific to that antigen; antibodies neutralise pathogens, opsonise them for phagocytosis, and activate complement. A subset becomes memory B-cells giving long-term immunity.
Allergy = exaggerated immune response to a normally harmless antigen (allergen). Mast cells and basophils, sensitised by IgE, release histamine → vasodilation (redness, swelling), increased capillary permeability (oedema), smooth muscle contraction (bronchoconstriction → wheezing), mucus secretion (runny nose), itching.
Vector: pBR322 (or pUC18). Essential properties: (i) origin of replication so it replicates inside the host; (ii) unique restriction sites within (iii) a selectable marker (antibiotic resistance gene) to identify transformed bacteria; small size; high copy number.
In-vitro DNA amplification using thermal cycling. Ingredients: template DNA, two primers, Taq polymerase, dNTPs, buffer with Mg²⁺. Steps: (1) Denaturation at 94–95°C — strands separate. (2) Annealing at 50–65°C — primers bind. (3) Extension at 72°C — Taq adds dNTPs. After ~30 cycles, ~10⁹ copies. Uses: forensics, diagnostics, cloning.
(i) Isolate human insulin mRNA from β-cells; make cDNA using reverse transcriptase. (ii) Insert the insulin gene into a plasmid using restriction enzymes and DNA ligase (sticky ends). (iii) Transform E. coli with the recombinant plasmid. (iv) Bacteria express human insulin; large-scale fermentation. (v) Insulin is harvested, purified and used to treat diabetes.
Endonucleases from bacteria that recognise specific palindromic DNA sequences (4–8 bp) and cut both strands, often leaving sticky ends with complementary overhangs. Used in molecular cloning to insert genes into plasmids. Examples: EcoRI (G↓AATTC), BamHI, HindIII.
Range = highest − lowest value. E.g. for 4, 7, 8, 12, 15 → range = 15 − 4 = 11. Percentile = value below which a given percentage of observations fall. E.g. the 90th percentile of test scores = the score below which 90% of students lie.
Mean = sum of values / number of values. Median = middle value when data are arranged in order. Mode = most frequently occurring value. Standard deviation = √(Σ(x−x̄)²/n) — measure of how spread out data are from the mean.
Bar chart — categorical data with counts/means (e.g. species abundance). Pie chart — proportions of a whole (e.g. blood-group %). Line / x-y scatter — continuous variable trends (e.g. enzyme rate vs. temperature). Always include axis labels, units, legend.
Structural homology. It implies a common evolutionary origin (descent from a shared ancestral molecule) and usually a related biological function — even when the underlying sequences may have diverged considerably.
Sequence homology = similarity in nucleotide / amino-acid sequence indicating evolutionary relationship. Structural homology = similar 3D folds. Databases: PDB (Protein Data Bank), UniProt, NCBI GenBank, EMBL.
(1) Target identification & lead-compound discovery — find a molecule that hits a disease-relevant protein. (2) Pre-clinical testing — in vitro & animal studies for safety and efficacy. (3) Clinical trials in 3 phases (safety in healthy volunteers → efficacy in patients → large-scale trials), then regulatory approval and post-market surveillance.
Volcanic eruptions (release CO₂ & SO₂ aerosols); solar irradiance variation; Milankovitch cycles (Earth's orbital changes); ocean currents (El Niño/La Niña). Effect of volcanism: large eruptions inject sulphate aerosols into the stratosphere, reflecting sunlight and cooling the planet for 1–3 years (e.g. Pinatubo 1991).
(i) Targeted drug delivery (cell-based logic gates that release drugs only in cancer cells). (ii) DNA data storage — millions of TB in a gram of DNA. (iii) Medical diagnostics inside the body — biosensors. (iv) Smart agriculture — engineered cells that report on soil/plant status.
Engineering of biological systems by designing & assembling novel genetic circuits or organisms with new functions. Example: engineered yeast producing artemisinin (anti-malarial); designer microbes producing biofuels; CAR-T cells engineered to attack cancer.
The three core events of urine formation in the nephron — see Ch Homeostasis Q3.
R atrium → tricuspid → R ventricle → pulmonary valve → lungs → L atrium → mitral → L ventricle → aortic valve → aorta. AV valves prevent backflow into atria during systole; semilunar valves prevent backflow into ventricles during diastole.
Ca²⁺ → troponin shift → cross-bridge cycle → ATP-powered actin–myosin sliding.
RMP → depolarisation (Na⁺ in) → repolarisation (K⁺ out) → restored by Na⁺/K⁺ pump. Saltatory in myelinated axons.
Antigen binding → activation → plasma cells secrete antibodies; memory B-cells provide long-term protection.
Cyclic in-vitro amplification of DNA using Taq polymerase, primers, dNTPs.
Section C (ERQ — 5–7 marks each). The orange MOST IMPORTANT tag marks the highest-yield long Q per chapter; purple MODEL PAPER means it is directly from the official Model Paper.
Cover: Bowman's capsule + glomerulus (ultrafiltration), PCT (bulk reabsorption), Loop of Henle (countercurrent multiplier), DCT (fine ionic adjustment under aldosterone), Collecting duct (water reabsorption under ADH). Include filtration vs reabsorption vs secretion, and the role of peritubular & vasa recta capillaries.
~70% as bicarbonate ions (HCO₃⁻): CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻ (catalysed by carbonic anhydrase in RBCs). HCO₃⁻ exchanged for Cl⁻ via band-3 protein (chloride shift). ~23% as carbamino-haemoglobin bound to globin amino groups. ~7% dissolved in plasma. Reverse process occurs at the lungs (low CO₂) → CO₂ exhaled.
Regions: cardiac → fundus → body → pyloric. Wall layers: mucosa (gastric glands), submucosa, muscularis externa (3 layers: longitudinal, circular, oblique — mechanical churning), serosa. Gastric pits with chief cells (pepsinogen), parietal cells (HCl + intrinsic factor), G-cells (gastrin), mucous cells (mucus). Pepsinogen → pepsin in HCl; pepsin starts protein digestion; HCl kills microbes & activates enzymes; gastric mixing → chyme; pyloric sphincter releases chyme into duodenum.
Pacemaker = SA node in the right atrium — sets heart rhythm (~70 bpm). Artificial pacemakers used in bradycardia, heart block, arrhythmia — a battery-powered device delivering electrical impulses via electrodes. Sequence: SA node fires → atrial depolarisation & contraction → impulse to AV node (slight delay) → down bundle of His → branches → Purkinje fibres → ventricular contraction from apex upward → atria relax, ventricles relax → cycle repeats.
(1) Haematoma formation — blood clot at fracture site (first hours/days). (2) Fibrocartilaginous (soft) callus — fibroblasts & chondroblasts form a soft bridge (3–4 weeks). (3) Bony (hard) callus — osteoblasts deposit spongy bone (~3 months). (4) Remodelling — osteoclasts & osteoblasts reshape the bone back to its original architecture (months–year).
Skeletal: striated, voluntary, multinucleated, attached to bone. Cardiac: striated, involuntary, branched, intercalated discs. Smooth: non-striated, involuntary, spindle-shaped, in walls of viscera. Sliding-filament: Ca²⁺ → troponin → tropomyosin shift → cross-bridge → ATP cycle.
Pituitary (master) — GH, TSH, ACTH, FSH/LH, prolactin, ADH, oxytocin. Thyroid — T3/T4 (BMR), calcitonin (↓Ca). Parathyroids — PTH (↑Ca). Pancreas (islets) — insulin (↓glucose), glucagon (↑glucose). Adrenals: cortex — cortisol, aldosterone, sex hormones; medulla — adrenaline, noradrenaline (fight/flight). Gonads — testes: testosterone (male traits, spermatogenesis); ovaries: oestrogen + progesterone (female cycle).
Forebrain: cerebrum (cortex — sensory/motor/association areas; left/right hemispheres), thalamus (relay), hypothalamus (homeostasis/endocrine link), limbic system (emotion/memory). Midbrain: visual/auditory reflexes, dopamine pathway. Hindbrain: cerebellum (balance, coordination), pons (relay, breathing rhythm), medulla oblongata (HR, BP, respiratory centres, reflexes — sneeze, cough, vomit).
Antigen binds B-cell receptor → activated (with helper-T-cell signal) → proliferates → plasma cells secrete antibodies + memory B-cells. Antibody structure: Y-shape, 2 heavy + 2 light chains held by S–S bonds; variable regions form 2 antigen-binding sites; constant region. Mode of action: neutralisation (block pathogen receptors), agglutination (clump), opsonisation (mark for phagocytes), complement activation (lysis), antibody-dependent cellular cytotoxicity (NK kills).
Mix: template DNA, forward + reverse primers, dNTPs, Taq polymerase, Mg²⁺ buffer. Thermocycler runs ~30 cycles, each cycle in 3 steps: (1) Denaturation 94–95°C — H-bonds break, strands separate. (2) Annealing 50–65°C — primers hybridise to flanking sequences. (3) Extension 72°C — Taq adds dNTPs 5'→3'. Each cycle doubles the target → 2ⁿ amplification (~10⁹ copies in 30 cycles). Applications: forensics (DNA fingerprinting), diagnostics, sequencing prep, cloning.
(i) Range shifts — species moving poleward / to higher altitudes as ranges warm. (ii) Phenological mismatch — breeding/migration timing decoupled from food availability. (iii) Habitat loss — polar ice melt, coral bleaching, drought. (iv) Ocean acidification harms shell-builders. (v) Disease spread — vector range expansion (mosquitoes). (vi) Extinction of specialists — polar bears, amphibians. (vii) Disrupted food webs and breeding behaviour. (viii) Heat stress, reduced fertility.
Production: immunise mouse with antigen → harvest B-cells from spleen → fuse with myeloma (cancerous) cells to form hybridomas (immortal + antibody-producing) → screen for clones producing the target antibody → mass-produce. Applications: pregnancy & diagnostic kits (anti-hCG); cancer therapy (trastuzumab/Herceptin against HER2+); autoimmune disease (infliximab for rheumatoid arthritis); targeted drug delivery; transplant rejection control.