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State Board · Class 12 · Biology

Lesson 10: Human Health and Diseases

7 concepts · 56 practice questions with answers · Free to read

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Immunity

Link to Std 9–10

Earlier lessons covered body systems; here we see how pathogens attack, how immunity fights back and how health is protected.

From daily life

A sneeze or cough — the body's first way of expelling germs.

Simple definition

Immunity = body's ability to fight pathogens. Health = complete physical, mental and social well-being.

ImmunityTypes of immunityInnateActivePassiveinbornown antibodiesready antibodiesInnate: barriers (skin, mucus, tears, saliva, HCl), cells, feverPhagocytes (neutrophils, macrophages), NK cells, interferon, complementAcquired: specificity, diversity, self/non-self recognition, memoryActive natural: after infection; active artificial: vaccine (polio, BCG)Passive natural: placenta, colostrum; artificial: serum (horse)Passive = short-lived; active = long-lasting (memory)Health = complete physical, mental and social well-being

In the figure : Innate, active and passive immunity.

Rule 1 : Innate immunity — Inborn and the same against all pathogens (non-specific). Physical barriers: skin, mucus, nasal hairs, lysozyme in tears/saliva, gastric HCl, salts in sweat. Physiological: fever (boosts interferon), acidity. Cellular: phagocytes (neutrophils, macrophages), NK (natural killer) cells. Chemical: interferons (antiviral proteins), complement system (30+ serum proteins).

  • Easy : Innate = non-specific.
  • Medium : Lysozyme = tears.
  • Exam-type (CET) : Interferon = antiviral.

Rule 2 : Acquired immunity — Acquired in life, specific. Features: specificity (for a particular antigen), diversity, self/non-self recognition, memory (first encounter slow; second quick and strong). Active: own antibodies; natural (after infection) and artificial (vaccines — polio, BCG). Passive: ready-made antibodies; natural (via placenta, then colostrum) and artificial (horse serum; snake-bite antiserum). Passive is short-lived; active long-lasting.

  • Easy : Colostrum = passive.
  • Medium : Vaccine = active artificial.
  • Exam-type (CET) : Memory = faster secondary response.
Remember

Innate = general; active = self-made; passive = borrowed.

Common mistake and CET trap

‘Colostrum gives active immunity’ is wrong (passive). Trap: ‘innate immunity is specific’ is wrong.

Shortcut

Memory clue : "Passive = pre-made; active = self-made".

Spot the difference

TypeInnateAcquired
SpecificityNoYes
MemoryNoYes

Practice questions

Easy
  1. 1Interferon acts against?
  2. 2Lysozyme occurs in?
  3. 3NK cells belong to?
Medium
  1. 4Colostrum gives?
  2. 5Vaccine gives?
  3. 6Benefit of memory?
Challenging
  1. 7Passive immunity duration?
  2. 8Complement proteins number?
Show answers (try them yourself first)
  1. 1Viruses.
  2. 2Tears, saliva.
  3. 3Innate.
  4. 4Natural passive immunity.
  5. 5Artificial active.
  6. 6Quicker second response.
  7. 7Short.
  8. 8More than 30.

Immune cells and antibodies

From daily life

Like an army: some fight directly, others identify the enemy and alert the rest.

Simple definition

An antigen = foreign substance triggering an immune response. An antibody = Y-shaped glycoprotein (immunoglobulin) that binds it.

Immune cellsImmune cells and the antibodyY2 heavy + 2 light chainsVariable region = paratopeHinge, disulphide bonds2000 molecules/s (plasma cell)B → plasmaT (thymus)B cells: bursal/gut tissue; AMIS (humoral); plasma cells → antibodiesT cells: thymus; CMIS; helper, cytotoxic (perforin), suppressor, memoryAntigen-presenting cells: macrophages present antigenAntibody roles: agglutination, opsonisation (phagocytosis), toxin neutralisationIg classes: IgG, IgA, IgM, IgE, IgDFirst contact = primary (slow); second = secondary (quick, strong)Vaccine = inactivated pathogen/antigen; builds memory cells

In the figure : B and T cells; antibody.

Live figure

Immune cells and antibodies

In the app you can move this figure with your finger.

Open in the app

Rule 1 : Lymphocytes: B and T — Main cells: lymphocytes and antigen-presenting cells (macrophages). B cells (bursal; gut-associated tissue — tonsils, Peyer’s patches) ⇒ antibody-mediated (humoral) immunity, AMIS; activated by antigen/helper T ⇒ multiply ⇒ plasma cells (antibodies ~2000 molecules/s) and memory B cells. T cells (thymus) ⇒ cell-mediated (CMIS); the clone includes helper T (help B cells), cytotoxic T (punch holes in infected cells with perforin), suppressor T (stop the response), memory T cells.

  • Easy : B → plasma cell → antibody.
  • Medium : T → thymus.
  • Exam-type (CET) : Cytotoxic = perforin.

Rule 2 : Structure and function of antibody — Y-shaped; 2 heavy + 2 light polypeptide chains joined by disulphide (–S–S–) bonds; a hinge joins arms and stem; each chain has a variable region (antigen-binding site = paratope; lock-and-key) and a constant region. Classes: IgG, IgA, IgM, IgE, IgD. Functions: agglutination (clumps germs ⇒ phagocytosis), opsonisation, toxin neutralisation (e.g. tetanus). Each antibody is specific to one antigen.

  • Easy : 4 chains: 2H + 2L.
  • Medium : Paratope = variable region.
  • Exam-type (CET) : Antibody = glycoprotein.
Remember

B = body fluids (antibodies); T = thymus, cell attack.

Common mistake and CET trap

‘T cells make antibodies’ is wrong (plasma cells). Trap: ‘antibody has 3 chains’ is wrong (4).

Shortcut

Memory clue : "4 chains = 2 heavy + 2 light = Y".

Spot the difference

CellImmunityOrigin
BAMISBursal/gut tissue
TCMISThymus

Practice questions

Easy
  1. 1What is an antibody?
  2. 2Chains in antibody?
  3. 3Where is paratope?
Medium
  1. 4Who makes antibodies?
  2. 5Perforin released by?
  3. 6AMIS stands for?
Challenging
  1. 7Role of suppressor T cells?
  2. 8Number of Ig classes?
Show answers (try them yourself first)
  1. 1Y-shaped glycoprotein.
  2. 22 heavy + 2 light.
  3. 3Variable region.
  4. 4Plasma cells.
  5. 5Cytotoxic T cells.
  6. 6Antibody-mediated immune system (B).
  7. 7Stop the response.
  8. 85.

Vaccination, allergy and autoimmunity

From daily life

Babies complete a vaccination card — to ‘introduce the enemy’ in advance.

Simple definition

Vaccination = giving an inactivated/weakened form of a pathogen to build immunity. Allergy = over-reaction to a harmless substance (allergen).

VaccinationVaccination, allergy and autoimmunityVaccineAllergyAutoimmunebuilds memoryIgE + histamineattacks selfVaccine: Edward Jenner (smallpox) and Pasteur (rabies)e.g. polio, BCG, DPT, hepatitis B, measles (MMR)Booster dose strengthens memory; vaccines safe, rare side effectsAllergens: dust, pollen, food; mast cells → histamine → sneezing, rashTreatment: antihistamine, adrenaline, steroidAutoimmune: rheumatoid arthritis, type 1 diabetes, lupusOrgan transplant: donor matching; immunosuppressants

In the figure : Vaccine, allergy, autoimmunity.

Rule 1 : Vaccination — A vaccine = inactivated pathogen or its antigen. It builds memory cells; a real infection is met by a quick response. A booster dose strengthens memory. E.g. polio, BCG, DPT, hepatitis B, MMR. Campaigns eliminated smallpox and nearly polio. Vaccines are safe; side effects rare; used only after trials. Alternative: serum (ready antibodies — snake bite, tetanus).

  • Easy : Vaccine = memory.
  • Medium : Booster = repeat dose.
  • Exam-type (CET) : Serum = ready antibodies.

Rule 2 : Allergy and autoimmunity — Allergy: allergens (dust, pollen, some foods, wool) ⇒ IgE ⇒ mast cells ⇒ histamine ⇒ sneezing, watery eyes, rash, sometimes anaphylaxis; treatment: antihistamines, adrenaline, steroids; avoid the allergen. Autoimmunity: attack on own cells (self/non-self recognition fails); e.g. rheumatoid arthritis, type 1 diabetes, lupus. Transplants: donor matching; immunosuppressants to prevent rejection.

  • Easy : Allergy: histamine.
  • Medium : IgE = allergy.
  • Exam-type (CET) : RA = autoimmune.
Remember

Histamine → sneezing.

Common mistake and CET trap

‘Vaccines give ready antibodies’ is wrong (memory). Trap: ‘autoimmune = attack on outside germs’ is wrong.

Shortcut

Memory clue : "A vaccine teaches before the real germ arrives".

Spot the difference

ConditionCause
AllergyIgE, histamine
AutoimmuneAttack on self

Practice questions

Easy
  1. 1Why a booster dose?
  2. 2Vaccine produces?
  3. 3Use of serum?
Medium
  1. 4Chemical in allergy?
  2. 5Immunoglobulin in allergy?
  3. 6Antihistamine does?
Challenging
  1. 7Autoimmune example?
  2. 8Drug in transplants?
Show answers (try them yourself first)
  1. 1To strengthen memory.
  2. 2Memory cells.
  3. 3Snake bite / tetanus.
  4. 4Histamine.
  5. 5IgE.
  6. 6Blocks histamine.
  7. 7Rheumatoid arthritis.
  8. 8Immunosuppressant.

Protozoan and worm diseases

From daily life

Mosquitoes breed in stagnant monsoon water and spread malaria.

Simple definition

A pathogen = disease-causing organism. A vector = carrier organism (mosquito). Incubation period = time between infection and symptoms.

Protozoa and wormsProtozoan and worm diseasesMalariaAmoebiasisAscariasisFilariasisPlasmodiumE. histolyticaAscarisW. bancroftiMalaria: female Anopheles; sporozoites; P. vivax, falciparum, malariae, ovaleFever cycle: haemozoin release → chills, fever; RBCs burst; liver → RBCAmoebiasis: contaminated food/water; faecal cysts; dysentery, crampsAscaris: eggs in contaminated food; intestinal blockage, anaemiaFilaria: Culex mosquito; lymph vessels blocked → elephantiasisPrevention: hygiene, mosquito control, boiled water

In the figure : Malaria, amoebiasis, ascariasis, filariasis.

Live figure

Protozoan and worm diseases

In the app you can move this figure with your finger.

Open in the app

Rule 1 : Malaria — Cause: Plasmodium — P. vivax, P. falciparum, P. malariae, P. ovale; P. falciparum is most serious (malignant). Vector: female Anopheles. When it bites, sporozoites enter blood ⇒ liver ⇒ multiply in RBCs ⇒ RBCs burst, releasing merozoites and toxic haemozoin ⇒ periodic chills and fever, anaemia. Life cycle: asexual in humans; sexual (gametocytes) in the mosquito. Prevention: stop mosquito breeding, nets, drugs.

  • Easy : Female Anopheles.
  • Medium : Haemozoin = fever.
  • Exam-type (CET) : P. falciparum = most serious.

Rule 2 : Amoebiasis, ascariasis, filariasis — Amoebiasis: Entamoeba histolytica; contaminated food/water (cysts); ulcers in large intestine ⇒ dysentery, cramps. Ascariasis: Ascaris lumbricoides (roundworm); eggs via contaminated food/hands; intestinal blockage, anaemia, pain. Filariasis (elephantiasis): Wuchereria bancrofti; vector Culex mosquito; blocked lymph vessels ⇒ swelling of limbs, scrotum. Prevention: hygiene, boiled water, handwashing, toilets, mosquito control.

  • Easy : Amoebiasis = dysentery.
  • Medium : Filaria: Culex.
  • Exam-type (CET) : Ascaris = roundworm.
Remember

Anopheles → malaria; Culex → filariasis.

Common mistake and CET trap

‘Male Anopheles spreads malaria’ is wrong (female). Trap: ‘Anopheles carries filariasis’ is wrong (Culex).

Shortcut

Memory clue : "M-A: malaria–Anopheles; F-C: filaria–Culex".

Spot the difference

DiseasePathogenVector/route
MalariaPlasmodiumAnopheles
FilariasisW. bancroftiCulex
AmoebiasisE. histolyticaContaminated water

Practice questions

Easy
  1. 1Cause of malaria?
  2. 2Vector of malaria?
  3. 3Most serious species?
Medium
  1. 4Cause of fever cycle?
  2. 5Amoebiasis pathogen?
  3. 6Ascaris is a?
Challenging
  1. 7Elephantiasis pathogen?
  2. 8Filaria vector?
Show answers (try them yourself first)
  1. 1Plasmodium.
  2. 2Female Anopheles.
  3. 3P. falciparum.
  4. 4Haemozoin.
  5. 5Entamoeba histolytica.
  6. 6Roundworm.
  7. 7Wuchereria bancrofti.
  8. 8Culex.

Bacterial, viral and fungal diseases

From daily life

Near someone with a cold, droplets spread through the air.

Simple definition

Typhoid = intestinal disease by Salmonella typhi. Dengue = viral fever spread by Aedes. Ringworm = fungal skin infection.

Germ diseasesBacterial, viral and fungal diseasesBacteriaVirusFungusTyphoid, pneumoniaDengue, coldRingwormTyphoid: Salmonella typhi; Widal test; fever, headache, abdominal painPneumonia: Streptococcus / Haemophilus; fluid in alveoli; coughCommon cold: rhinovirus; nose and throat; droplet spreadDengue: Aedes mosquito; chikungunya: Aedes; fever, joint painRingworm: Microsporum, Trichophyton, Epidermophyton; circular skin patchesVector mosquitoes; clean water, vaccination, keeping dryIncubation period: gap between infection and symptoms

In the figure : Bacterial, viral, fungal diseases.

Rule 1 : Bacterial diseases — Typhoid: Salmonella typhi; contaminated food/water; sustained fever, headache, abdominal pain, loss of appetite; diagnosed by Widal test; intestine may perforate. Pneumonia: Streptococcus pneumoniae, Haemophilus influenzae; fluid in alveoli; fever, cough, breathing trouble; by droplets. Treatment: antibiotics; vaccines exist. Others: tuberculosis (Mycobacterium), tetanus, cholera. Prevention: hygiene, vaccination, boiled water.

  • Easy : Typhoid: Widal test.
  • Medium : Pneumonia: alveoli.
  • Exam-type (CET) : Antibiotics for bacteria.

Rule 2 : Viral and fungal diseases — Common cold: Rhinovirus; nose, throat; sneezing, runny nose, cough; droplet spread; antibiotics useless. Dengue, chikungunya: Aedes mosquito; fever, headache, joint pain, rash; treatment: rest, fluids; prevent mosquito breeding. Ringworm: Microsporum, Trichophyton, Epidermophyton; circular itchy patches on skin, hair, nails; warm damp places; keep dry, use separate towels. Antibiotics do not work on viruses; vaccines and hygiene matter.

  • Easy : Dengue: Aedes.
  • Medium : Ringworm: fungus.
  • Exam-type (CET) : Cold: Rhinovirus.
Remember

Typhoid → Widal → Salmonella typhi.

Common mistake and CET trap

‘Antibiotics treat a cold’ is wrong (virus). Trap: ‘ringworm is a worm’ is wrong (fungus).

Shortcut

Memory clue : "Aedes = dengue; Anopheles = malaria; Culex = filaria".

Spot the difference

DiseaseCause
TyphoidSalmonella typhi
Common coldRhinovirus
RingwormMicrosporum…

Practice questions

Easy
  1. 1Typhoid pathogen?
  2. 2Widal test diagnoses?
  3. 3Pneumonia affects?
Medium
  1. 4Common cold virus?
  2. 5Dengue vector?
  3. 6Ringworm cause?
Challenging
  1. 7Antibiotics act on?
  2. 8Incubation period?
Show answers (try them yourself first)
  1. 1Salmonella typhi.
  2. 2Typhoid.
  3. 3Alveoli.
  4. 4Rhinovirus.
  5. 5Aedes.
  6. 6Fungi.
  7. 7Bacteria.
  8. 8Time from infection to symptoms.

Cancer and AIDS

From daily life

A vine without a fence spreads everywhere; cancer cells grow without control.

Simple definition

Cancer = uncontrolled cell division. AIDS = loss of immunity as HIV destroys helper T cells.

Cancer, AIDSCancer and AIDSCancer: uncontrolled cell divisionAIDS: HIV → helper T ↓Benign (local) vs malignant (metastasis)Carcinogens: physical (X-ray, UV), chemical (tobacco), biological (viruses)Types: carcinoma, sarcoma, leukaemia, lymphomaDiagnosis: biopsy, CT, MRI; treatment: surgery, radiation, chemotherapy, α-interferonHIV: retrovirus, RNA; reverse transcriptase → DNASpread: unprotected sex, infected blood/needles, mother to childNot by touch, food or mosquito; test: ELISAPrevention: safe blood, sterile needles, awareness (NACO)

In the figure : Cancer and AIDS.

Rule 1 : Cancer — Normal cells obey contact inhibition; cancer cells do not ⇒ tumour. Benign: local, does not spread. Malignant: invades neighbours and metastasises through blood/lymph. Carcinogens: physical (X-rays, γ-rays, UV), chemical (tobacco smoke, asbestos), biological (some viruses; oncogenes). Types: carcinoma (epithelium), sarcoma (connective), leukaemia (WBC), lymphoma. Diagnosis: biopsy, CT, MRI, blood tests. Treatment: surgery, radiation, chemotherapy, α-interferon. Prevention: avoid smoking/tobacco.

  • Easy : Metastasis = malignant.
  • Medium : Carcinoma = epithelium.
  • Exam-type (CET) : Biopsy = diagnosis.

Rule 2 : AIDS — Cause: HIV — retrovirus, RNA genome; reverse transcriptase makes DNA from RNA; integrates into host DNA; destroys helper T cells ⇒ weak immunity ⇒ opportunistic infections (TB, pneumonia, cancers). Spread: unprotected sex, infected blood/needles, mother to child (womb, birth, milk). Not spread by: touch, handshake, food, mosquitoes, living together. Diagnosis: ELISA, Western blot. Prevention: safe blood, sterile needles, education, awareness (NACO); treatment: antiretrovirals (slow progression).

  • Easy : HIV = retrovirus.
  • Medium : Helper T destroyed.
  • Exam-type (CET) : ELISA = test.
Remember

Benign stays; malignant moves.

Common mistake and CET trap

‘AIDS spreads by mosquitoes’ is wrong. Trap: ‘benign tumours metastasise’ is wrong.

Shortcut

Memory clue : "HIV attacks helper T cells".

Spot the difference

TypeBenignMalignant
SpreadNoMetastasis
DangerLowHigh

Practice questions

Easy
  1. 1Contact inhibition is lost in?
  2. 2What is metastasis?
  3. 3Carcinogen example?
Medium
  1. 4Leukaemia affects?
  2. 5Diagnostic procedure?
  3. 6HIV is a?
Challenging
  1. 7AIDS does not spread by?
  2. 8Test for HIV?
Show answers (try them yourself first)
  1. 1Cancer cells.
  2. 2Spread of cancer to other sites.
  3. 3Tobacco smoke / UV.
  4. 4WBC.
  5. 5Biopsy.
  6. 6Retrovirus.
  7. 7Touch / mosquito.
  8. 8ELISA.

Adolescence and addiction

From daily life

Peer pressure — the urge to do something wrong because ‘everyone does it’.

Simple definition

Adolescence = ages 10–19; period between childhood and adulthood. Addiction = compulsive use of a substance despite harm.

AdolescenceAdolescence and addiction10–19 yearsOpioidsCannabinoids / CocaAdolescence: from secondary sexual characters to end of growthChanges: growth spurt, mood swings, identity search, peer influenceOpioids: from poppy (morphine, heroin); cannabinoids: cannabisCoca alkaloids: cocaine; alcohol, tobacco (nicotine): legal but harmfulEffects: liver/lung/brain damage, accidents, cancer; withdrawal symptomsPrevention: communication, counselling, sports/hobbies, avoiding bad companyHelp: parents, teachers, doctors, rehabilitation centres

In the figure : Adolescence and addiction.

Rule 1 : Adolescence — From secondary sexual characters until growth ends; 10–19 years; three phases (early, middle, late). Physical changes: growth spurt, maturation of reproductive organs, secondary characters (voice breaking, hair in boys; breast development, menstruation in girls). Emotional/social: identity search, mood swings, peer influence. Mental health: irritability, anxiety, depression; many disorders begin at this age; talking to parents/teachers and counselling help.

  • Easy : 10–19 years.
  • Medium : Peer influence.
  • Exam-type (CET) : Communication + counselling.

Rule 2 : Addiction and drug abuse — Opioids: from the poppy — morphine, heroin, codeine; depress the nervous system. Cannabinoids: cannabis. Coca alkaloids: cocaine. Alcohol and tobacco (nicotine): legal but harmful. Effects: liver (cirrhosis), lungs (emphysema, cancer), brain, heart; accidents, crime, family stress; withdrawal symptoms on stopping. Prevention: sports/hobbies, protecting children from pressure, advice, learning to say ‘no’. Help: parents, teachers, doctors, rehabilitation centres. Treatment only under medical supervision.

  • Easy : Opioids: poppy.
  • Medium : Nicotine: tobacco.
  • Exam-type (CET) : Help: doctors, rehab.
Remember

Learn to say no; asking for help is not shameful.

Common mistake and CET trap

‘Legal means safe’ is wrong. Trap: ‘addiction can always be quit alone’ is wrong.

Shortcut

Memory clue : "Opioids → poppy; cocaine → coca; cannabinoids → hemp".

Spot the difference

GroupSourceExample
OpioidsPoppyMorphine
CannabinoidsCannabisBhang
Coca alkaloidsCocaCocaine

Practice questions

Easy
  1. 1Adolescent age range?
  2. 2Source of opioids?
  3. 3Cocaine comes from?
Medium
  1. 4Chemical in tobacco?
  2. 5What is withdrawal?
  3. 6Organ harmed by alcohol?
Challenging
  1. 7A preventive step?
  2. 8Who can help?
Show answers (try them yourself first)
  1. 110–19 years.
  2. 2Poppy.
  3. 3Coca plant.
  4. 4Nicotine.
  5. 5Symptoms on stopping.
  6. 6Liver.
  7. 7Sports / counselling.
  8. 8Parents, doctors, rehab centres.

Quick revision of the whole lesson

ConceptKey fact
ImmunityInnate = non-specific; acquired = memory
AntibodyY; 2H + 2L; plasma cells
VaccineMemory cells; booster
MalariaPlasmodium; female Anopheles
Germ diseasesTyphoid–Widal; dengue–Aedes
Cancer / AIDSMetastasis; HIV–helper T–ELISA
AddictionOpioids, cannabinoids, coca; seek help

🎯 Most important points for the exam

  • Innate and acquired immunity.
  • B, T cells and antibody.
  • Vaccine, allergy, autoimmunity.
  • Malaria, amoebiasis, filaria.
  • Typhoid, dengue, ringworm.
  • Cancer and AIDS.
  • Adolescence and addiction.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.