NEET Biology Formula Sheet

Each level is a taxon. Species is the basic unit of classification. Binomial nomenclature assigns a two-part Latin name: $\text{Genus + species epithet}$ (e.g., $\textit{Homo sapiens}$).

Monera: prokaryotes (bacteria, cyanobacteria); Protista: unicellular eukaryotes; Fungi: heterotrophic, cell wall of chitin; Plantae: autotrophic, cell wall of cellulose; Animalia: heterotrophic, no cell wall.

$d$ is the resolving power (limit of resolution), $\lambda$ is the wavelength of light/electron beam, $n$ is the refractive index, $\theta$ is the half-angle of the cone of light entering the objective.

Human erythrocyte membrane. Lipids include phospholipids, cholesterol, and glycolipids. Integral proteins span the membrane; peripheral proteins are on the surface.

$V$ is the reaction velocity; $V_{\max}$ is the maximum reaction velocity at substrate saturation; $[S]$ is the substrate concentration; $K_m$ is the Michaelis constant (substrate conc. at half $V_{\max}$). Lower $K_m$ means higher enzyme-substrate affinity.

$k_{\text{cat}}$ is the catalytic constant (turnover number); $V_{\max}$ is maximum velocity; $[E_T]$ is the total enzyme concentration. Carbonic anhydrase is one of the fastest known enzymes.

$n$ is the number of amino acid residues in the polypeptide chain. Each peptide bond (–CO–NH–) is formed by a dehydration/condensation reaction releasing one water molecule.

$A$, $T$, $G$, $C$ are the number of Adenine, Thymine, Guanine, Cytosine bases; $N$ is the number of base pairs; A–T pairs have 2 hydrogen bonds; G–C pairs have 3 hydrogen bonds.

$G_1$ is the first gap phase (growth); $S$ is the synthesis phase (DNA replication); $G_2$ is the second gap phase; $M$ is mitosis. Interphase accounts for approximately 95% of the total cell cycle duration.

$n$ is the number of divisions (mitotic) or the number of primary cells undergoing meiosis. In spermatogenesis, 1 primary spermatocyte yields 4 sperms. In oogenesis, 1 primary oocyte yields 1 ovum + 3 polar bodies.

$n$ represents the haploid chromosome number; $C$ represents the haploid DNA content. $2n$ = diploid, $2C$ = DNA amount in a diploid G1 cell, $4C$ = DNA amount after S phase replication.

$\Psi_w$ is water potential; $\Psi_s$ is solute/osmotic potential (always negative); $\Psi_p$ is pressure/turgor potential; $i$ is ionization constant; $C$ is molar concentration; $R$ is gas constant; $T$ is absolute temperature. DPD = Diffusion Pressure Deficit; OP = Osmotic Pressure; TP = Turgor Pressure.

$\Psi_{\text{solution}}$ is the water potential of the external solution; $\Psi_{\text{cell}}$ is the water potential of the cell sap. Incipient plasmolysis occurs when turgor pressure ($\Psi_p$) = 0.

$h\nu$ represents light energy (photons); 12 water molecules are the source of oxygen ($6\text{O}_2$); $\text{C}_6\text{H}_{12}\text{O}_6$ is glucose. Minimum 8 photons required to release 1 molecule of $\text{O}_2$.

Non-cyclic photophosphorylation involves both PS I and PS II. Cyclic photophosphorylation involves only PS I and produces ATP only. The Calvin cycle requires 18 ATP and 12 NADPH to fix 6 CO₂ into 1 glucose.

The Calvin cycle has 3 stages: Carbon fixation (RuBisCO), Reduction, and Regeneration of RuBP. For each CO₂ fixed, 3 ATP and 2 NADPH are consumed. Net product for 6 turns = 1 glucose (G3P).

C₃ plants have higher compensation point due to photorespiration losses. C₄ plants have a CO₂-concentrating mechanism (Hatch-Slack pathway) that virtually eliminates photorespiration.

36 ATP if malate-aspartate shuttle is used (in heart/liver); 38 ATP is the older estimate. The revised estimate of 30–32 accounts for the actual H⁺/ATP ratio across the inner mitochondrial membrane.

Glycolysis occurs in cytoplasm; Krebs cycle and ETC in mitochondria. 10 NADH × 2.5 = 25 ATP; 2 FADH₂ × 1.5 = 3 ATP; 4 substrate-level ATP. Total ≈ 32 ATP (revised).

RQ indicates the type of substrate being respired. Carbohydrates give RQ = 1 (balanced exchange). Fats need more O₂ (RQ < 1). Organic acids like malic acid yield RQ > 1 (e.g., RQ for malic acid = 1.33).

Alcoholic fermentation occurs in yeast producing ethanol and CO₂. Lactic acid fermentation occurs in animal muscle cells under oxygen debt. Both produce only 2 ATP per glucose (substrate-level phosphorylation in glycolysis).

DW = dry weight of plant tissue. 17 essential elements include C, H, O (from air/water) + 6 macronutrients + 8 micronutrients. Critical concentration is the concentration below which plant growth is retarded.

Nitrogenase is a Mo-Fe protein that requires anaerobic conditions. The reaction requires 16 ATP per N₂ fixed. Leghemoglobin in root nodules provides the microaerobic environment. H₂ is an obligatory byproduct.

Water moves from higher water potential (soil) to lower water potential (leaf mesophyll → atmosphere). The transpiration pull (cohesion-tension theory) is the dominant mechanism. Root pressure is insufficient alone for tall trees.

Sucrose is actively loaded into sieve tube elements at source, lowering water potential and drawing water from xylem. At sink, sucrose is unloaded, increasing water potential. The resulting turgor pressure gradient drives bulk flow.

$W_1$ and $W_2$ are initial and final size/mass at times $t_1$ and $t_2$; $r$ is the specific growth rate; $W_0$ and $W_t$ are sizes at time 0 and $t$ respectively.

Ratios are based on F₂ generation from true-breeding parents. Monohybrid cross involves 1 trait; Dihybrid cross involves 2 independent traits. Test cross involves crossing F₁ hybrid with homozygous recessive parent.

All are modifications of the standard 9:3:3:1 dihybrid ratio. Incomplete dominance shows blending (e.g., red × white → pink snapdragons). Codominance: both alleles express (e.g., ABO blood groups).

$p$ is the frequency of the dominant allele ($A$); $q$ is the frequency of the recessive allele ($a$); $p^2$ = freq. of $AA$; $2pq$ = freq. of $Aa$; $q^2$ = freq. of $aa$. Five conditions: large population, random mating, no mutation, no migration, no selection.

$X^C$ is the X-chromosome with the normal allele; $X^c$ is the X-chromosome with the recessive allele; $Y$ lacks the corresponding gene. X-linked recessive conditions predominantly affect males as they are hemizygous.

RF = recombination frequency; cM = centiMorgan (1 map unit). Linked genes show RF < 50%. Greater physical distance = higher RF. Genes on different chromosomes show 50% recombination (independent assortment).

Multiplication rule applies for independent events occurring together. Addition rule applies for mutually exclusive outcomes. Used extensively in pedigree analysis to predict probability of affected offspring.

$I^A$ and $I^B$ are codominant alleles producing A and B antigens on RBC surface. $i$ is recessive producing no antigen. AB is universal recipient (no antibodies); O is universal donor (no antigens).

$N$ is the total number of base pairs. Distance between adjacent base pairs = 0.34 nm. The right-handed B-DNA has a major groove and a minor groove. Sugar-phosphate backbone is on the outside.

$A$ = Adenine, $T$ = Thymine, $G$ = Guanine, $C$ = Cytosine. Chargaff's rule applies ONLY to double-stranded DNA. In single-stranded DNA or RNA, $A \neq T(U)$ and $G \neq C$.

$n$ is the number of replication rounds. Semi-conservative replication means each daughter DNA retains one parental strand. Proved by Meselson-Stahl experiment using ¹⁵N (heavy) and ¹⁴N (light) isotopes.

Each codon = 3 consecutive nucleotide bases on mRNA. $N$ = total nucleotides in the coding region of mRNA. The '-1' accounts for the stop codon which is not translated. The genetic code is degenerate (multiple codons for same amino acid) but non-ambiguous.

Template strand is complementary and antiparallel to mRNA. Coding strand has the same sequence as mRNA (except T→U). In prokaryotes, RNA polymerase is a single enzyme; in eukaryotes: RNA Pol I (rRNA), Pol II (mRNA), Pol III (tRNA).

HGP used two key approaches: BAC (Bacterial Artificial Chromosome) and Shotgun sequencing. Less than 2% of the genome codes for proteins; the rest includes introns, repetitive sequences, and regulatory elements.

The digits represent: $\frac{\text{Incisors . Canines . Premolars . Molars}}{\text{Incisors . Canines . Premolars . Molars}}$ per half jaw. Heterodont (different types) and thecodont (embedded in sockets) dentition. Diphyodont = two sets in lifetime.

Fats provide maximum energy per gram (2.25× more than carbohydrates). These values are used in calculating BMR (Basal Metabolic Rate) and dietary energy requirements.

Stroke Volume is the blood pumped per heartbeat ($\approx 70$ mL). Heart Rate averages $\approx 72$ beats/min at rest. CO varies with exercise (can increase to 20–25 L/min).

The cardiac cycle includes systole (contraction) and diastole (relaxation). SA node (pacemaker) generates 72 impulses/min. The conduction sequence: SA node → AV node → Bundle of His → Purkinje fibres.

TV is the air inhaled/exhaled in a normal breath. IRV is extra air that can be forcibly inhaled. ERV is extra air that can be forcibly exhaled. RV is air remaining after maximum exhalation.

VC is the maximum air that can be exhaled after maximum inhalation. TLC includes all four volumes. FRC is the air remaining after normal exhalation.

$\text{GFR}$ = Glomerular Filtration Rate; $P_{\text{GHP}}$ = Glomerular Hydrostatic Pressure ($\approx 60$ mmHg); $P_{\text{BCOP}}$ = Blood Colloid Osmotic Pressure ($\approx 32$ mmHg); $P_{\text{CHP}}$ = Capsular Hydrostatic Pressure ($\approx 18$ mmHg). About 99% of filtrate is reabsorbed.

The loop of Henle acts as a countercurrent multiplier creating an increasing osmolarity gradient from cortex to inner medulla. Vasa recta acts as a countercurrent exchanger maintaining this gradient. ADH controls water reabsorption from collecting duct.

Plasma contains 90–92% water, 6–8% proteins (albumin, globulins, fibrinogen). Formed elements = RBCs + WBCs + Platelets. RBCs are enucleated and biconcave in mammals. Lifespan: RBC ≈ 120 days, WBC ≈ varies, Platelets ≈ 7–10 days.

Resting potential maintained by Na⁺/K⁺ ATPase pump (3 Na⁺ out, 2 K⁺ in). Depolarization: Na⁺ influx via voltage-gated channels. Repolarization: K⁺ efflux. Saltatory conduction in myelinated neurons (node to node).

Insulin lowers blood glucose (from β-cells of Langerhans); Glucagon raises it (from α-cells). PTH increases blood Ca²⁺; Calcitonin (TCT from thyroid C-cells) decreases it. T₃/T₄ from thyroid regulate BMR.

C = Cervical, T = Thoracic, L = Lumbar, S = Sacrum (5 fused → 1), Co = Coccyx (4 fused → 1). Smallest bone: Stapes (middle ear). Longest bone: Femur. Total in newborn ≈ 300 (many fuse during growth).

A-band contains thick myosin filaments (constant length). I-band contains thin actin filaments. H-zone is the central part of A-band without actin overlap. Z-line anchors actin filaments. M-line is the center of the sarcomere.

Spermatogenesis produces 4 functional sperms per primary spermatocyte. Oogenesis produces 1 functional ovum per primary oocyte (3 polar bodies degenerate). Meiosis I reduces chromosome number; Meiosis II separates chromatids.

FSH stimulates follicular growth; LH surge triggers ovulation on Day 14. Corpus luteum produces progesterone during luteal phase. If no fertilization, corpus luteum degenerates → drop in progesterone → menstruation.

Trophoblast forms placenta; inner cell mass forms embryo. Placenta is connected by umbilical cord. hCG (human chorionic gonadotropin) is produced by trophoblast — basis of pregnancy tests.

$N$ = population size; $t$ = time; $r$ = intrinsic rate of natural increase (biotic potential); $N_0$ = initial population; $e$ = Euler's number ($\approx 2.718$); $K$ = carrying capacity. When $N = K$, growth rate = 0. When $N = K/2$, growth rate is maximum.

$N_t$ = population density at time $t$; $B$ = births; $I$ = immigration; $D$ = deaths; $E$ = emigration. $B$ and $I$ increase population; $D$ and $E$ decrease it.

Expanding population: broad-based pyramid (high birth rate). Stable population: column-shaped. Declining population: inverted/urn-shaped (low birth rate, high proportion of elderly).

$\text{GPP}$ = Gross Primary Productivity (total photosynthesis); $\text{NPP}$ = Net Primary Productivity (biomass available to consumers); $R_p$ = respiratory losses by producers.

$E_n$ = energy at trophic level $n$. Only 10% is transferred; 90% is lost as heat (respiration), excretion, and decomposition. This limits food chains to typically 4–5 trophic levels.

Carbon cycles through atmosphere, biosphere, hydrosphere, and lithosphere. Photosynthesis and respiration are the major biological processes. Fossil fuel burning and deforestation increase atmospheric CO₂.

$S$ = species richness; $A$ = area; $Z$ = regression slope (typically $0.1$ to $0.2$ for small areas within a continent; $0.6$ to $1.2$ for very large areas like continents); $C$ = Y-intercept (varies with taxonomic group).

LC = Least Concern, NT = Near Threatened, VU = Vulnerable, EN = Endangered, CR = Critically Endangered, EW = Extinct in Wild, EX = Extinct. India is one of 17 mega-diversity countries (Paul Myers).

BOD is measured as mg of O₂ consumed per litre of water sample over 5 days at 20°C. Higher BOD = more organic pollutants = more microbial decomposition = more dissolved O₂ depletion.

Greenhouse gases trap infrared radiation reflected from Earth's surface. CFCs also deplete the ozone layer. Montreal Protocol (1987) banned CFCs. Kyoto Protocol (1997) set emission reduction targets.

$E$ = genus $\textit{Escherichia}$; $co$ = species $\textit{coli}$; $R$ = strain RY13; $I$ = first enzyme isolated. Palindromic sequences read the same on both strands (5'→3'). Sticky ends have overhangs; blunt ends have no overhang.

$n$ = number of PCR cycles (typically 25–35). Uses thermostable $\textit{Taq}$ polymerase (from $\textit{Thermus aquaticus}$). Each cycle doubles the DNA. 30 cycles produce $2^{30} \approx 10^9$ copies from a single molecule.

kb = kilobase pairs. Plasmids are the most common vectors (e.g., pBR322, pUC). BAC = Bacterial Artificial Chromosome; YAC = Yeast Artificial Chromosome. Vectors must have origin of replication (ori), selectable marker, and cloning site.

$Bt$ = $\textit{Bacillus thuringiensis}$. Cry proteins are inactive protoxins that become active (toxic) in alkaline insect gut (pH > 9.5). They create pores in the midgut epithelium, causing cell lysis and death of the insect.

ADA = Adenosine Deaminase, essential for immune function. SCID patients lack functional T and B lymphocytes. Gene therapy introduces a functional copy of the ADA gene into the patient's own bone marrow cells or lymphocytes.

H chain = Heavy chain (determines class: γ, α, μ, ε, δ). L chain = Light chain (κ or λ). Antigen-binding site = variable region of H + L chains. Each antibody has 2 antigen-binding sites (bivalent).

Sexual cycle (gametogony) occurs in mosquito (definitive host). Asexual cycle in human (intermediate host): liver stage (schizogony) → blood stage (erythrocytic schizogony). Merozoite release causes RBC lysis → fever.

$2n$ = diploid number (two copies of each chromosome); $n$ = haploid number (one copy). Meiosis halves the chromosome number. Fertilization restores the diploid number. Polyploidy = having more than 2n chromosomes.

The embryo sac = female gametophyte. Egg apparatus = egg cell + 2 synergids (at micropylar end). 3 antipodal cells at chalazal end. Central cell has 2 polar nuclei that fuse with one sperm → triploid endosperm (3n).

Both events = double fertilization (unique to angiosperms, discovered by S.G. Nawaschin). Endosperm provides nutrition to the developing embryo. In some plants (e.g., orchids, Alisma), endosperm development is suppressed.

Each microspore mother cell (2n) undergoes meiosis to produce a tetrad of 4 microspores. Each microspore develops into a pollen grain (male gametophyte) with 2 cells: vegetative (tube) cell and generative cell.

Each ovule needs 1 pollen tube (with 2 sperms) for double fertilization. 1 anther typically has 4 pollen sacs (microsporangia). True fruit develops from ovary only; false fruit includes other floral parts (e.g., thalamus in apple).

Cu-T releases copper ions that are spermicidal. Hormonal methods inhibit ovulation and alter cervical mucus. Surgical methods are permanent. MTP (Medical Termination of Pregnancy) is legal in India up to 20 weeks (extended to 24 weeks for special categories under MTP Act 2021).

IVF-ET = In Vitro Fertilization and Embryo Transfer. ZIFT transfers zygote/early embryo into fallopian tube. GIFT = Gamete Intra-Fallopian Transfer (gametes, not zygote). AI is simplest ART for cases of low sperm count.

$\oplus$ = actinomorphic; $\%$ = zygomorphic; $\bigcirc$ = bisexual; $K$ = calyx; $C$ = corolla; $P$ = perianth (tepals); $A$ = androecium; $G$ = gynoecium; $(\;)$ = fusion; $\overline{G}$ = superior ovary; $\underline{G}$ = inferior ovary.

Phyllotaxy determines the fraction of stem circumference between successive leaves. In alternate phyllotaxy, the fraction is typically 1/2, 1/3, 2/5, 3/8, etc. following the Fibonacci series.

Dendrochronology = study of annual rings to determine tree age and past climate. Spring wood (early wood) has wider vessels; autumn wood (late wood) has narrower vessels. Vascular cambium produces secondary xylem (inward) and secondary phloem (outward).

Coelom = body cavity lined by mesoderm on both sides. Schizocoelom develops from splitting of mesoderm (protostomes). Enterocoelom develops from archenteron pouches (deuterostomes: Echinodermata, Chordata).

Head bears compound eyes (mosaic vision, ~2000 ommatidia each), antennae, and mouthparts (biting and chewing type). Blood (haemolymph) is colourless; open circulatory system with 13-chambered dorsal heart. Excretion by Malpighian tubules + uricotelic.

Biogas is produced in anaerobic digesters (biogas plants). Cattle dung (gobar) is the substrate. Three stages: hydrolysis → acidogenesis → methanogenesis. Methanogens are obligate anaerobes found in rumen of cattle and sewage treatment sludge.

BOD = Biochemical Oxygen Demand. Primary effluent → aeration tanks (aerobic microbes reduce organic matter) → settling tanks → effluent released. Anaerobic digester processes sludge → biogas (CH₄). Clean effluent should have BOD < 30 mg/L.