Biology and Life Sciences

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Cell — The Basic Unit of Life

All living organisms are made of cells. The cell theory (Schleiden, Schwann, 1839):

1. All living organisms are composed of cells
2. The cell is the basic unit of life
3. All cells arise from pre-existing cells (Rudolf Virchow, 1855)

Types of Cells:

Feature	Plant Cell	Animal Cell
Cell wall	✅ Present (cellulose)	❌ Absent
Chloroplast	✅ Present	❌ Absent
Vacuole	Large, central	Small, many
Centrioles	❌ Absent (mostly)	✅ Present
Shape	Rectangular, fixed	Irregular
Lysosomes	Rare	Abundant

Cell Organelles & Their Functions:

• Nucleus: Contains DNA, controls cell activities; contains nucleolus (makes ribosomes)
• Mitochondria: “Powerhouse of cell” — produces ATP (adenosine triphosphate) via respiration
• Endoplasmic Reticulum (ER): Rough ER (ribosomes attached → protein synthesis); Smooth ER (lipid synthesis)
• Golgi Apparatus: Modifies, packages, and ships proteins (called “post office of cell”)
• Lysosomes: Contain digestive enzymes — digest worn-out organelles and foreign particles
• Chloroplast: Site of photosynthesis — contains chlorophyll (green pigment)
• Ribosomes: Site of protein synthesis (free in cytoplasm or attached to ER)
• Cell membrane: Selectively permeable — controls what enters/exits the cell (Fluid Mosaic Model)

⚡ UPTET tip: The mitochondria is called the “powerhouse” because it produces the most ATP through cellular respiration.

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Photosynthesis

The process by which green plants make food using sunlight, carbon dioxide, and water:

$$6CO_2 + 6H_2O \xrightarrow{\text{sunlight/chlorophyll}} C_6H_{12}O_6 + 6O_2$$

Two Stages:

Light Reaction (Grana/thylakoid membrane):

• Chlorophyll absorbs light energy
• Water splits: $2H_2O \rightarrow 4H^+ + 4e^- + O_2$
• Photolysis of water produces O₂
• ATP and NADPH₂ produced
• Occurs only in presence of light

Dark Reaction / Calvin Cycle (Stroma):

• CO₂ is fixed into glucose using ATP and NADPH₂
• Doesn’t directly need light (but needs products of light reaction)
• Occurs in stroma of chloroplast

C3 and C4 Plants:

• C3 plants: Rice, wheat, barley — first product is 3-carbon compound (phosphoglyceric acid)
• C4 plants: Maize, sugarcane, sorghum — first product is 4-carbon compound (oxaloacetic acid); more efficient in hot climates

⚡ UPTET tip: “Photophosphorylation” = making ATP using light energy. Cyclic: only ATP produced. Non-cyclic: ATP + NADPH₂ both produced.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Cell Division — Mitosis and Meiosis

Mitosis (Equational Division):

• One parent cell → two identical daughter cells
• Chromosome number: Maintained (2n → 2n)
• Purpose: Growth, repair, asexual reproduction
• Stages: Prophase → Metaphase → Anaphase → Telophase (PMAT)
  • Prophase: Chromatin condenses → chromosomes visible; nuclear membrane dissolves
  • Metaphase: Chromosomes line up at equator; spindle fibers attach to centromeres
  • Anaphase: Sister chromatids separate → move to opposite poles
  • Telophase: Nuclear membrane reforms; chromosomes become chromatin again

Meiosis (Reduction Division):

• One parent cell → four non-identical daughter cells (gametes)
• Chromosome number: Halved (2n → n)
• Purpose: Formation of gametes (sex cells), introduces genetic variation
• Two divisions: Meiosis I (reduction) + Meiosis II (equational)
  • Meiosis I: Homologous chromosomes pair and separate (crossing over occurs — genetic recombination)
  • Meiosis II: Sister chromatids separate (like mitosis)

Feature	Mitosis	Meiosis
Divisions	One	Two
Daughter cells	2	4
Genetic variation	No	Yes (crossing over)
Chromosome number	Same as parent	Half of parent
Where	All somatic cells	Germ cells

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Human Body Systems

Digestive System:

• Parts: Mouth → Pharynx → Oesophagus → Stomach → Small intestine (duodenum, jejunum, ileum) → Large intestine (caecum, colon, rectum) → Anus
• Small intestine: Main site of absorption; has villi (finger-like projections) and microvilli
• Digestive enzymes:
  • Salivary amylase (mouth): Breaks starch → maltose
  • Pepsin (stomach): Proteins → peptides
  • Trypsin (pancreas): Proteins → peptides
  • Lipase (pancreas): Fats → fatty acids + glycerol
  • Maltase, sucrase, lactase (intestine): Disaccharides → monosaccharides

Respiratory System:

• Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli (gas exchange site)
• Breathing mechanism: Diaphragm contracts → volume increases → pressure decreases → air rushes in (inspiration)
• Tidal volume: Normal breath = ~500 mL; Vital capacity = ~4500 mL

Circulatory System:

• Heart: 4 chambers — RA, RV, LA, LV; mammals have double circulation (pulmonary + systemic)
• Blood vessels: Arteries (carry blood from heart, thick walls), Veins (carry to heart, valves), Capillaries (exchange sites)
• Blood components: Plasma (55%) + Blood cells (45%)
  • Red blood cells: Carry O₂ (haemoglobin); no nucleus; live ~120 days
  • White blood cells: Fight infection (neutrophils, lymphocytes, monocytes, eosinophils, basophils)
  • Platelets: Blood clotting (thrombocytes); live 8-9 days
• Blood groups: ABO system (A, B, AB, O) and Rh factor (+ or −)

Excretory System:

• Kidneys (bean-shaped, retroperitoneal) → Ureters → Urinary bladder → Urethra
• Nephron = functional unit of kidney:
  1. Glomerular filtration (water + waste from blood)
  2. Tubular reabsorption (water, glucose, amino acids back into blood)
  3. Tubular secretion (extra waste products secreted into tubule)
• Urine composition: Water (95%), urea, creatinine, uric acid, salts

Nervous System:

• CNS: Brain (forebrain, midbrain, hindbrain) + Spinal cord
• PNS: Somatic (voluntary) + Autonomic (involuntary — sympathetic, parasympathetic)
• Reflex arc: Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle/gland)
• Synapse: Junction between two neurons; uses neurotransmitters (acetylcholine, dopamine, serotonin)

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Genetics — Inheritance and Variation

Mendel’s Laws:

1. Law of Dominance: In a heterozygote, the dominant allele masks the recessive allele
2. Law of Segregation: During gamete formation, paired factors (alleles) separate; each gamete gets one allele
3. Law of Independent Assortment: Alleles of different genes segregate independently during gamete formation (only true for genes on different chromosomes)

Key Genetic Terms:

• Allele: Alternate form of a gene
• Genotype: Genetic makeup (e.g., TT, Tt, tt)
• Phenotype: Physical appearance (e.g., tall, short)
• Homozygous: Same alleles (TT or tt)
• Heterozygous: Different alleles (Tt)
• Dominant: Expressed in heterozygote (T)
• Recessive: Only expressed in homozygote (t)

Punnett Square Examples:

• Monohybrid cross: Tt × Tt → 3 Tall (TT, Tt, Tt) : 1 Short (tt) = 3:1 ratio
• Test cross: Tt × tt → 1 Tall (Tt) : 1 Short (tt) = 1:1 ratio

Sex Determination:

• Human: XX (female) / XY (male) — determined by father
• Male produces X and Y sperm (50:50); Female produces only X eggs
• Sex ratio at birth: ~105 males : 100 females

Human Genetic Disorders:

Disorder	Type	Cause	Symptoms
Colour blindness	Sex-linked (X)	Recessive X^b	Can’t distinguish red/green
Haemophilia	Sex-linked (X)	Recessive X^h	Blood doesn’t clot
Down syndrome	Autosomal	Trisomy 21 (extra chromosome 21)	Mental retardation, flat face
Turner syndrome	Sex chromosomal	XO (45 chromosomes)	Female, short stature, infertility
Klinefelter syndrome	Sex chromosomal	XXY (47 chromosomes)	Male, tall, some female traits

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Nutrition and Health

Nutrients — Types and Sources:

Nutrient	Function	Sources
Carbohydrates	Main energy source (4 kcal/g)	Rice, wheat, sugar
Proteins	Growth and repair (4 kcal/g)	Pulses, eggs, meat, milk
Fats	Energy storage (9 kcal/g)	Oil, ghee, butter, nuts
Vitamins	Regulate body processes	Fruits, vegetables (A,B,C,D,E,K)
Minerals	Body functions (Ca, Fe, K, Na)	Milk (Ca), spinach (Fe)
Water	Solvent, transport, temperature	60-70% of body weight

Vitamins — Key Facts for UPTET:

• Vitamin A (Retinol): Night vision, healthy skin — deficiency: night blindness, xerophthalmia — sources: carrots, papaya, fish liver oil
• Vitamin B1 (Thiamine): Energy metabolism — deficiency: Beriberi — sources: whole grains, nuts
• Vitamin C (Ascorbic acid): Collagen synthesis, immunity — deficiency: Scurvy (bleeding gums) — sources: citrus fruits, amla
• Vitamin D (Calciferol): Calcium absorption — deficiency: Rickets (bone deformities) — sources: sunlight, fish, milk
• Vitamin K: Blood clotting — deficiency: excessive bleeding — sources: green leafy vegetables

⚡ UPTET exam question: “Which vitamin is produced by our body when exposed to sunlight?” → Vitamin D (cholecalciferol synthesized in skin)

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Diseases and Immunity

Common Human Diseases:

Disease	Causative Agent	Vector/Transmission	Symptoms
Malaria	Plasmodium (protozoa)	Female Anopheles mosquito	Fever, chills, anaemia
Dengue	Dengue virus	Aedes aegypti mosquito	High fever, rash, joint pain
Typhoid	Salmonella typhi (bacteria)	Contaminated food/water	High fever, weakness
Tuberculosis	Mycobacterium tuberculosis	Air (coughing/sneezing)	Persistent cough, weight loss
AIDS	HIV (Retrovirus)	Blood, sexual contact, mother-child	Weakens immunity
Pneumonia	Bacteria/virus	Air	Lung infection, fever
cholera	Vibrio cholerae	Contaminated water	Severe diarrhoea

Immunity:

• Innate (non-specific): Skin, mucous membranes, tears, stomach acid, phagocytes
• Acquired (specific):
  • Humoral (B-cells): Produces antibodies against antigens
  • Cell-mediated (T-cells): Directly destroys infected cells
• Active immunity: Body produces antibodies (slow, long-lasting) — either natural (infection) or artificial (vaccination)
• Passive immunity: Antibodies given directly (fast, short-lasting) — either natural (maternal antibodies in breast milk) or artificial (antivenom, gamma globulin)

⚡ UPTET tip: Vaccines work on the principle of acquired immunity — they contain weakened/inactivated pathogens that stimulate the immune system without causing disease. This is called “artificial active immunity.”

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