Biology Formula Sheet - NEET Essential Calculations and Relationships

📋 Introduction

This biology formula sheet contains all essential calculations, numerical relationships, and mathematical concepts needed for NEET preparation. While biology is primarily conceptual, certain topics require numerical understanding and calculations.

🧬 Genetics Formulas

Mendelian Genetics

Monohybrid Cross:
Parental: AA × aa
F₁ generation: All Aa (heterozygous)
F₂ generation ratio: 3:1 (dominant:recessive)
Genotypic ratio: 1:2:1 (AA:Aa:aa)

Dihybrid Cross:
Parental: AABB × aabb
F₁ generation: All AaBb
F₂ generation phenotypic ratio: 9:3:3:1
F₂ generation genotypic ratio: 1:2:1:2:4:2:1:2:1

Probability Calculations:
P(A and B) = P(A) × P(B) (independent events)
P(A or B) = P(A) + P(B) - P(A and B)
P(A|B) = P(A and B)/P(B) (conditional probability)

Population Genetics

Hardy-Weinberg Equilibrium:
p + q = 1 (where p = frequency of dominant allele, q = frequency of recessive allele)
p² + 2pq + q² = 1 (genotype frequencies)
p² = frequency of homozygous dominant (AA)
2pq = frequency of heterozygous (Aa)
q² = frequency of homozygous recessive (aa)

Calculations:
If frequency of recessive phenotype = q²
Then q = √(frequency of recessive phenotype)
p = 1 - q
2pq = 2(1 - q)q = frequency of carriers

Genetic Drift:
Change in allele frequency due to random events
More pronounced in small populations

Linkage and Recombination

Recombination Frequency:
RF = (Number of recombinant offspring/Total offspring) × 100%
1% recombination = 1 map unit = 1 centimorgan (cM)

Genetic Distance:
Map distance = Recombination frequency
If RF > 50%, genes are unlinked

Coefficient of Coincidence:
CO = Observed double crossovers/Expected double crossovers
Interference = 1 - CO

🔬 Biochemistry and Cell Biology

pH and Buffer Calculations

pH Scale:
pH = -log[H⁺]
[H⁺] = 10^(-pH)
pOH = -log[OH⁻]
pH + pOH = 14 (at 25°C)

Acid-Base Calculations:
pH = pKa + log([A⁻]/[HA]) (Henderson-Hasselbalch equation)
For weak acid HA ⇌ H⁺ + A⁻
Ka = [H⁺][A⁻]/[HA]
pKa = -log(Ka)

Buffer Capacity:
β = ΔB/ΔpH
Where ΔB = moles of acid/base added, ΔpH = change in pH
Optimal buffer when pH = pKa

Enzyme Kinetics

Michaelis-Menten Equation:
v = (Vmax × [S])/(Km + [S])
Where v = reaction velocity, [S] = substrate concentration
Vmax = maximum velocity, Km = Michaelis constant

Lineweaver-Burk Plot:
1/v = (Km/Vmax)(1/[S]) + 1/Vmax
Double reciprocal plot
y-intercept = 1/Vmax, x-intercept = -1/Km

Turnover Number (kcat):
kcat = Vmax/[E]total
Number of substrate molecules converted per enzyme per second

Cell Division Timing

Cell Cycle Duration:
Total cell cycle time = T₁ + T₂ + T₃ + T₄
Where T₁ = G₁ phase, T₂ = S phase, T₃ = G₂ phase, T₄ = M phase

Mitotic Index:
MI = (Number of cells in mitosis/Total number of cells) × 100
Used to study cell proliferation rates

DNA Content Calculations:
C-value = DNA content per haploid set
2C = DNA content in G₁ phase
4C = DNA content in G₂ and M phases

🫁 Physiology Formulas

Human Physiology

Cardiac Output:
CO = Stroke Volume × Heart Rate
Normal CO = 5 L/min
Stroke Volume = End Diastolic Volume - End Systolic Volume

Blood Pressure:
Mean Arterial Pressure (MAP) = Diastolic Pressure + (Pulse Pressure)/3
Pulse Pressure = Systolic Pressure - Diastolic Pressure

Respiratory Calculations:
Tidal Volume (VT) = 500 mL (normal)
Vital Capacity = IRV + TV + ERV
Total Lung Capacity = VC + RV
Respiratory Quotient (RQ) = CO₂ eliminated/O₂ consumed

Glomerular Filtration Rate (GFR):
GFR = (Urine flow rate × Urine concentration)/Plasma concentration
Normal GFR = 125 mL/min
Filtration Fraction = GFR/RPF (Renal Plasma Flow)

Plant Physiology

Photosynthesis:
6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O
Light-dependent reactions produce ATP and NADPH
Calvin cycle consumes ATP and NADPH

Chlorophyll Concentration:
Measured using spectrophotometer
Absorbance at 645 nm and 663 nm
Total chlorophyll = 20.2(A₆₄₅) + 8.02(A₆₆₃)

Transpiration Rate:
Measured using potometer
Factors affecting: light, temperature, humidity, wind

Growth Rate:
Absolute Growth Rate (AGR) = Change in size/Time
Relative Growth Rate (RGR) = (1/size) × (Change in size/Time)

Ecology Calculations

Population Growth:
dN/dt = rN(1 - N/K) (Logistic growth)
Where N = population size, r = intrinsic growth rate, K = carrying capacity

Exponential Growth: N(t) = N₀e^(rt)
Doubling Time: t₂ = ln(2)/r

Population Density:
Density = Number of individuals/Area or Volume
Quadrat method for plants
Mark-recapture method for animals

Ecological Efficiency:
Energy transfer efficiency = (Energy at trophic level n)/(Energy at trophic level n-1) × 100
Typical efficiency: 10% (10% law)

Biodiversity Indices:
Simpson's Index: D = Σnᵢ(nᵢ - 1)/[N(N - 1)]
Shannon Index: H' = -Σpᵢ ln(pᵢ)
Where pᵢ = proportion of species i

🔬 Laboratory Techniques

Spectrophotometry

Beer-Lambert Law:
A = εcl
Where A = absorbance, ε = molar absorptivity, c = concentration, l = path length

Concentration Calculations:
c = A/(εl)
For known standards, plot calibration curve

DNA Quantification:
A260 = 1.0 corresponds to 50 μg/mL double-stranded DNA
A260/A280 ratio ~1.8 for pure DNA
A260/A230 ratio ~2.0-2.2 for pure DNA

Protein Quantification:
A280 depends on aromatic amino acid content
Bradford assay: Colorimetric method

Centrifugation

Relative Centrifugal Force (RCF):
RCF = 1.118 × 10⁻⁵ × r × (rpm)²
Where r = radius in cm, rpm = revolutions per minute

Sedimentation Coefficient:
S = v/ω²r
Where v = velocity, ω = angular velocity, r = radius

Chromatography

Retention Factor (Rf):
Rf = Distance traveled by solute/Distance traveled by solvent
Used in paper chromatography and TLC

Resolution (Rs):
Rs = 2(d₂ - d₁)/(w₁ + w₂)
Where d₁, d₂ = distances of two peaks, w₁, w₂ = peak widths

📊 Biotechnology Formulas

Molecular Biology

DNA Concentration Calculations:
[DNA] = (A260 × 50 μg/mL)/Dilution factor
For double-stranded DNA: 1 A260 unit = 50 μg/mL
For single-stranded DNA: 1 A260 unit = 33 μg/mL
For RNA: 1 A260 unit = 40 μg/mL

PCR Calculations:
Number of copies = (Amount of DNA × Avogadro's number)/(Length × 660)
Amplification factor = 2ⁿ where n = number of cycles

Tm (Melting Temperature):
Tm = 4°C × (number of G/C base pairs) + 2°C × (number of A/T base pairs)
For primers 14-20 bp long

Protein Analysis

Protein Concentration:
Bradford assay: Use standard curve with BSA
Lowry assay: Colorimetric method
Biuret assay: Based on peptide bonds

Molecular Weight Determination:
SDS-PAGE: Compare with molecular weight markers
Log(MW) vs Rf plot for standard curve

🎯 Statistical Analysis in Biology

Experimental Design

Sample Size:
n = (Zα/2 × σ/E)²
Where Zα/2 = critical value, σ = standard deviation, E = margin of error

Standard Error:
SE = σ/√n
Where σ = standard deviation, n = sample size

Confidence Interval:
CI = x̄ ± (Zα/2 × SE)
Where x̄ = sample mean

Growth Curves

Bacterial Growth Phases:
Lag phase: No increase in cell number
Log phase: Exponential growth N = N₀e^(kt)
Stationary phase: Growth rate = death rate
Decline phase: Death rate > growth rate

Generation Time:
g = t/n
Where t = time period, n = number of generations
g = 0.301/(log₁₀N - log₁₀N₀)

📊 Essential Constants

Biological Constants

Avogadro's number: 6.022 × 10²³ mol⁻¹
Gas constant: 8.314 J/(mol·K)
Boltzmann constant: 1.381 × 10⁻²³ J/K
Planck's constant: 6.626 × 10⁻³⁴ J·s
Speed of light: 3 × 10⁸ m/s

Physiological Constants:
Normal human body temperature: 37°C = 98.6°F = 310 K
Normal blood pH: 7.35-7.45
Normal atmospheric pressure: 760 mmHg = 1 atm = 101.3 kPa

🎯 Usage Tips

Problem-Solving Strategy:

1. Identify the concept involved in the problem
2. Write down the relevant formula with all variables
3. Substitute known values with proper units
4. Solve systematically showing all steps
5. Verify the answer using reasonable biological limits

Common Mistakes to Avoid:

• Unit conversions: Always ensure consistent units
• Percentage calculations: Remember to divide by 100
• Logarithm bases: Use correct base (10 for log, e for ln)
• Probability rules: Apply correct probability formulas
• Genetic ratios: Check dominant/recessive relationships

📈 Performance Metrics

Mastery Levels:

• Level 1: Basic formula recognition
• Level 2: Formula application with guidance
• Level 3: Independent problem solving
• Level 4: Complex multi-step calculations
• Level 5: Research-level numerical analysis

Use this biology formula sheet as your quick reference guide for NEET preparation! While biology is primarily conceptual, these numerical relationships are crucial for complete understanding and exam success. 🎯