Comprehensive Study Notes on Micronutrients, Cell Injury, Homeostasis, Cancer & HIV/AIDS

Micronutrients: General Concepts

Micronutrients = vitamins (organic) + minerals (inorganic)
- Required in small amounts yet essential for metabolism, growth, and disease prevention.
- Human body makes very few of them → dietary intake mandatory.
Vitamins
- Organic, carbon-based compounds used with minimal chemical change.
- Each vitamin executes specific biochemical roles (co-enzymes, antioxidants, hormone-like regulators, etc.).
- Classification by solubility:
- Water-soluble: dissolve in water; not stored → daily intake required; excess excreted in urine. Examples: Vitamin C and B-complex.
- Fat-soluble: dissolve in lipids; stored in adipose & liver; can accumulate → toxicity risk. Examples: Vitamins A, D, E, K.
Minerals
- Inorganic ions or elements originating from soil → taken up by plants → enter food chain.
- Two quantitative classes:
- Macro-minerals: present in body > $5\,\text{g}$ ; required in gram or hundreds-of-milligram amounts/day.
- Trace minerals: needed in microgram–milligram ranges; deficiency/excess equally dangerous.

Overview of Major Vitamins, Functions & Dietary Sources

Vitamin A (Retinoids / provitamin A carotenoids)
- Roles: night vision (rhodopsin), epithelial integrity, immunity, bone & reproductive health.
- Sources: liver, fish-liver oils, eggs, dairy, dark-green & orange produce (carrots, sweet potato, mango → β-carotene precursor).
- Toxicity (‘‘hypervitaminosis A’’): dry skin, alopecia, headaches, hepatotoxicity, blurred vision.
- Deficiency: night-blindness → xerophthalmia → irreversible blindness.
Vitamin C (L-ascorbic acid)
- Antioxidant, collagen synthesis, iron absorption enhancer, immune support.
- Sources: citrus, guava, berries, tomatoes, bell peppers, broccoli, spinach.
- Toxicity (> $1000\,\text{mg}$ per dose): diarrhea, GI distress, rebound scurvy on abrupt cessation.
- Deficiency: classic scurvy – bleeding gums, petechiae, poor wound healing, fatigue.
Vitamin D (Calciferols)
- Regulates $\text{Ca}^{2+}$ & $\text{PO}_4^{3-}$ absorption/ deposition → bone & tooth mineralization; immunomodulation.
- Sources: cutaneous synthesis via UV-B, fatty fish, egg yolk, fortified milk.
- Toxicity (supplement excess): hypercalcemia → nausea, nephrocalcinosis, arrhythmias.
- Deficiency: rickets (children), osteomalacia (adults).
Vitamin E (Tocopherols/tocotrienols)
- Lipid-phase antioxidant guarding cell membranes & LDL; aids immune & wound healing.
- Sources: wheat-germ oil, vegetable oils, nuts/seeds, whole grains, leafy greens, egg yolk.
- Toxicity (rare; mega-doses) → bleeding tendency, ↓ vit A stores.
- Deficiency (rare) → myopathy, neuropathy, hemolysis.
Vitamin K (K₁ phylloquinone, K₂ menaquinone)
- Cofactor for γ-carboxylation of clotting factors II, VII, IX, X; regulates bone $\text{Ca}^{2+}$ binding proteins.
- Sources: green leafy veg (K₁), gut flora & fermented foods (K₂), animal products (meats, eggs, cheese).
- Synthetic K₃ (menadione) toxic in high doses.
- Deficiency → bleeding diathesis, osteopenia; newborns & antibiotic users at risk.

Water-Soluble Vitamin Details (B-Complex + C)

• B₁ (Thiamin)

Coenzyme TPP in carbohydrate → ATP metabolism; nerve conduction.
Food: pork, fish, legumes, nuts, whole/enriched grains.
Deficiency: Beriberi (dry → neuropathy; wet → edema), Wernicke-Korsakoff in alcoholics; symptoms include weakness, depression, appetite loss.
Nontoxic.
• B₂ (Riboflavin)
Part of FMN & FAD for redox reactions; RBC formation, skin & vision health.
Destroyed by light → milk in opaque cartons.
Deficiency: angular cheilitis, glossitis, seborrheic dermatitis, eye fatigue; risk ↑ in alcoholics, cataract pts, sickle-cell.
Nontoxic.
• B₃ (Niacin)
NAD/NADP coenzymes for energy metabolism; nicotinic acid lowers LDL & raises HDL.
Body makes limited niacin from tryptophan.
Toxicity: “niacin flush”, GI upset, hepatotoxicity at $50–100\,\text{mg}$ ; niacinamide comparatively safe.
Deficiency: Pellagra – “3 D’s”: dermatitis, diarrhea, dementia (± death). Fortification largely eliminated it.
• B₆ (Pyridoxine/-al/-amine)
PLP coenzyme: aa metabolism, heme synthesis, converts tryptophan → niacin, neurotransmitter synthesis, immune support.
Deficiency: irritability, neuropathy, glossitis, dermatitis; high-dose supplement (> $500\,\text{mg/day}$ ) → neurotoxicity.
• B₁₂ (Cobalamin)
DNA synthesis (methionine synthase), odd-chain FA metabolism, myelin maintenance, RBC maturation.
Only in animal foods; vegans need fortified foods or supplements.
Malabsorption in elderly (↓ intrinsic factor) → pernicious anemia, neuropathy.
Non-toxic.
• Vitamin C ➝ see earlier section for full profile.

Fat-Soluble Vitamin Recap (Toxicity risk ↑)

Summarized above; note stability & cooking effects: vit A heat-stable, vit D destroyed by flour bleaching agents.

Macro-Minerals

• Sodium (Na⁺)

Extracellular fluid/osmotic balance, nerve impulse, BP regulation.
Excess: hypernatremia, hypertension → ↑ cardiovascular risk; deficiency rare.
• Chloride (Cl⁻)
Works with Na⁺ & K⁺ for fluid pH balance; component of gastric HCl.
Deficiency uncommon; excess parallels high NaCl diets.
• Potassium (K⁺)
Major intracellular cation → membrane potential, heart rhythm, nerve transmission.
Food: unprocessed produce > processed foods.
Hypokalemia → weakness, arrhythmia; hyperkalemia (supplements/renal failure) → cardiac arrest.
• Calcium (Ca²⁺)
Bone/teeth structure (~ $99\%$ body Ca), muscle contraction, clotting, signaling.
Deficiency: osteopenia/osteoporosis; toxicity → nephrolithiasis, calcification.
• Phosphorus (P; $\text{PO}_4^{3-}$ )
Bone matrix, ATP, phospholipids, nucleic acids.
Excess (esp. renal disease) exacerbates secondary hyperparathyroidism.
• Magnesium (Mg²⁺)
Cofactor for > $300$ enzymes (ATP reactions), cardiac function.
Deficiency (GI loss, alcoholism) → tetany, arrhythmia; toxicity (renal fail) → respiratory paralysis.
• Sulfur (S)
Constituent of cysteine, methionine, taurine, biotin; skin, hair, nails integrity.
Deficiency/toxicity rare; brittle nails can signal low S intake.

Trace Minerals and Heavy Metals

• Iron (Fe)

Hemoglobin/myoglobin O₂ transport, cytochromes.
Absorption ↑ with vit C (chelates Fe³⁺).
Deficiency → microcytic anemia, pallor, fatigue; excess (hemochromatosis) damages liver & heart.
• Zinc (Zn)
Cofactor for > $100$ enzymes, immune function, wound healing, growth/puberty.
Deficiency: growth delay, hypogonadism, taste loss; excess → GI irritation.
• Iodine
Thyroxine (T₄)/T₃ synthesis → metabolic rate, neuro-development.
Soil depletion & inland living risk goiter/cretinism; iodized salt solves.
• Selenium (Se)
Component of glutathione peroxidase (antioxidant), thyroid hormone metabolism.
Deficiency: Keshan disease (cardiomyopathy), immune dysfunction; toxicity → brittle hair/nails.
• Copper (Cu)
Collagen cross-linking (lysyl oxidase), iron metabolism, neurotransmitters.
Menkes (defect in Cu absorption) vs Wilson’s (toxic accumulation).
Citrus juices enhance Cu²⁺ uptake (chelation).
• Manganese (Mn)
Co-factor for superoxide dismutase, metabolism.
Excess inhalation (miners) → neurotoxicity parkinsonism.
• Fluoride (F⁻)
Enamel & bone remineralization; deficiency → dental caries; excess (fluorosis) mottled teeth/bone.
Sources: fluoridated water, tea, toothpaste.
• Chromium (Cr)
Potentiates insulin → glucose homeostasis; deficiency mimics diabetes.
• Molybdenum (Mo)
Cofactor (xanthine oxidase, sulfite oxidase); deficiency rare.
• Heavy metals (Pb, Hg, Cd)
Environmental contaminants → bioaccumulate; compete with essential minerals; renal & neuro damage.

Nutritional Deficiency Diseases & Countermeasures

Iron → anemia; Iodine → goiter.
Protein-energy malnutrition in children:
- Kwashiorkor: protein deficiency post-weaning; edema, hepatomegaly.
- Marasmus: total calorie/protein deficit; severe wasting.
Combating strategies: nutrient-rich diets, food fortification, supplements, biofortification (GMO), soil selenium supplementation.

Cell Injury, Adaptation & Death

• Cell populations

Labile (continuous division), Stable (quiescent but capable), Amitotic (permanent).
• Stress → cellular adaptations:
Hypertrophy (↑ size), Hyperplasia (↑ number), Atrophy (↓ size).
If adaptation fails → reversible injury → irreversible injury → cell death.

Necrosis vs Apoptosis

Feature	Apoptosis	Necrosis
Cause	Programmed signals (intrinsic/extrinsic)	Acute injury, ischemia, toxins
Energy	Requires ATP	No
Cells affected	Single/few	Groups
Membrane	Intact → blebs → apoptotic bodies	Rupture → contents spill
Inflammation	None	Yes
Nuclear changes	DNA cleavage into ladders	Pyknosis → karyorrhexis → karyolysis

• Types of necrosis:

Coagulative (ischemic organs), Liquefactive (brain abscess), Caseous (TB), Fat (pancreatitis, breast trauma), Fibrinoid (vessel walls, autoimmune).
• Apoptotic pathways:
Intrinsic/mitochondrial (BAX opening pores → cytochrome c → caspase-9).
Extrinsic/death-receptor (Fas/TNF → caspase-8).
AIF (caspase-independent DNA fragmentation).
• Balance: too much apoptosis → atrophy/neurodegeneration; too little → cancer, atherosclerosis.

Homeostasis Mechanisms

Thermoregulation

Core temp ≈ $37^{\circ}\text{C}$ .
Cooling: sweating (evaporative heat loss), vasodilation (↑ cutaneous blood flow).
Warming: vasoconstriction, shivering, piloerection, behavioral (huddling).
Surface-area-to-volume (SA:V) rule: higher SA:V accelerates heat loss.

Glucose Homeostasis

Pancreatic β-cells secrete insulin → ↓ blood glucose (store as glycogen in liver/muscle).
α-cells release glucagon → glycogenolysis + gluconeogenesis → ↑ glucose.
Other gut-brain hormones: leptin (satiety), ghrelin (hunger), CCK, GIP, GLP-1.
Diabetes mellitus: insulin deficiency/resistance → chronic hyperglycemia.
- Fasting safe range $<7.0\,\text{mmol L}^{-1}$ ; borderline $7.0–10.0$ ; critical $>10.0$ ; coma risk $<1.0$ (hypo) or $>13.0$ (hyper).

Energy Storage & Fasting

Excess carbs → glycogen (limited) then fat.
Post-exercise window ≈ 2 h for glycogen resynthesis (simple CHO helpful).
Prolonged fasting: glycogen depleted → lipolysis & gluconeogenesis (aa → glucose); metabolic rate falls.

Water & Osmoregulation

General intake: $\approx 80\,\text{oz} \,(2.4\,\text{L})$ daily OR body weight (lb)/2 (oz). Add $12\,\text{oz}$ per extra $25\,\text{lb}$ overweight.
Kidneys: filter plasma → selective reabsorption (all glucose, variable H₂O/ions) → excrete urea + excess water as urine.
Filtrate path: blood → renal artery → glomerulus → tubule → ureter → bladder → urethra.

Biochemistry of Cancer

• Cancer = malignant neoplasm; uncontrolled proliferation, invasion, metastasis.
• Benign vs malignant:

Benign: localized, encapsulated, slow, non-invasive.
Malignant: invasive, rapid, potential for metastasis.
• Hallmarks/biochemical traits:
Self-sufficiency in growth signals (oncogenes RAS, MYC, EGFR).
Insensitivity to anti-growth signals (loss of tumor suppressors p53, APC, BRCA1/2).
Evasion of apoptosis; limitless replication; sustained angiogenesis; tissue invasion & metastasis.
• Warburg effect: cancer cells rely on aerobic glycolysis → ↑ lactic acid (acidosis), even with O₂.
• Carcinogenesis steps: DNA damage → failed repair → mutations → oncogene activation & tumor-suppressor loss → clonal expansion → angiogenesis → tumor.
• Etiologic agents:
Physical: ionizing & UV radiation (pyrimidine dimers).
Chemical (≈ $80\%$ of cancers): polycyclic hydrocarbons, aromatic amines, nitrosamines, aflatoxin B₁, asbestos, vinyl chloride, heavy metals, industrial dusts.
Biological: oncogenic viruses (EBV → Burkitt, HPV → cervical, HBV → hepatoma, HTLV-1 → adult T-cell leukemia, KSHV → Kaposi).
Hormonal: estrogen (endometrium), anabolic steroids (liver), OCPs (breast).
• Tumor markers (diagnosis/prognosis): AFP (liver/testes), CEA (colon, ↑ smokers), PSA (prostate), β-hCG (choriocarcinoma), Calcitonin (medullary thyroid), Bence-Jones (myeloma), PAP (prostate acid phosphatase).

Biochemistry of HIV/AIDS

Global & Historical Snapshot

≈ $40\,\text{million}$ living with HIV; > $25\,\text{million}$ deaths. First cluster recognized 1981 (Pneumocystis pneumonia, Kaposi sarcoma).

HIV Structure & Genome

Enveloped retrovirus (lentivirus).
Envelope glycoproteins: gp120 (binds CD4) + gp41 (fusion).
Matrix p17, capsid p24 (diagnostic antigen), RNA genome ×2 + enzymes RT, integrase, protease.
Genes:
- gag (p24, p17), pol (RT p64/p51, protease p10, integrase p32), env (gp160 → gp120/gp41).
- Regulatory/accessory: tat, rev, nef, vif, vpr, vpu/vpx, LTR.
Variants: HIV-1 (groups M [A–J], O, N, P) & HIV-2 (West Africa, less pathogenic).

Lifecycle Summary

Attachment gp120 → CD4 + coreceptor (CCR5/CXCR4).
Fusion via gp41; uncoating.
Reverse transcription (error-prone → high mutation).
Integration (integrase) → provirus latency.
Transcription/translation; protease cleavage; assembly; budding & maturation.

Immunopathogenesis

Progressive CD4⁺ T-cell depletion → impaired cellular immunity.
Reversal of $T4:T8$ ratio; B-cell hypergammaglobulinemia with poor specificity.
Opportunistic infections & malignancies (Kaposi, lymphoma) cause morbidity & mortality.

Clinical Stages

Acute seroconversion: flu-like; p24 + RNA positive; antibodies negative (window).
Asymptomatic latency: may last $>10$ years; contagious. CD4 declines gradually.
Persistent Generalized Lymphadenopathy; AIDS-related complex (weight > $10\%$ loss, fever, diarrhea).
AIDS: CD4 < $200/\mu L$ or AIDS-defining illness (PCP pneumonia, Kaposi, CNS lymphoma, etc.).

Laboratory Diagnosis

Non-specific: leukopenia, lymphopenia, ↓ platelets, ↑ IgG/IgA, reversed CD4/CD8.
Specific tests:
- p24 capture ELISA (earliest antigen).
- Antibody ELISA (1st→4th gen). 4th gen “Duo” detects p24 + Ab (window ≈ $2$ weeks).
- Confirm by Western blot (env + gag bands).
- PCR for viral RNA/DNA (detects early, monitors load).
- Rapid tests: dot-blot, agglutination, comb, oral fluid, urine.

Treatment

Goal: maintain CD4 > $350$ , achieve undetectable viral load.
Antiretrovirals:
- Nucleoside RT inhibitors (NRTIs) e.g., AZT.
- Non-nucleoside RT inhibitors (NNRTIs) e.g., Nevirapine.
- Protease inhibitors.
- HAART: 2 NRTIs + 1 PI/NNRTI (multi-class) → suppresses replication at multiple stages.
Investigational: CCR5/CXCR4 blockers, gene-edited T cells.
Immunotherapy (cytokines, passive Ab) unproven.

Prevention & Obstacles to Vaccine

Safe sex, screened blood, needle hygiene; zidovudine reduces vertical transmission.
Vaccine challenges: rapid antigenic drift, cell-mediated immunity requirement, proviral latency.

Ethical & Public-Health Implications

Hidden hunger (micronutrient deficiency) prevalent in low-income regions → fortification & biofortification essential.
Hyper-vitamin supplementation risks (fat-solubles, niacin, B₆ neuropathy).
Environmental contaminants (heavy metals, industrial carcinogens) demand regulation (e.g., asbestos bans).
HIV/AIDS stigma → confidentiality, equitable drug access, maternal-child preventive programs.
Cancer screening markers (PSA, CEA, AFP) carry false-positive/negative ethical dilemmas; informed consent critical.