Maharashtra State Board · Class 10 · Biology · Chapter 6

Cell — Structure and Micro-Organisms — Formula Sheet

Board Formulas

7 formulas

1.Cell Theory★
$All living things are made of cells; cells arise from pre-existing cells.$
Schleiden, Schwann and Virchow. Foundational statement of biology.
2.Bacterial Growth
$N = N_{0} \times 2^{n}$
Bacteria divide by binary fission. n = number of generations, N₀ = starting count.
3.Doubling Time
$N = N_{0} \times 2^{t / T_{d}}$
T_d = doubling time (~20 min for E. coli under ideal conditions).
4.Cell Size and SA:V Ratio★
$\frac{S A}{V} = \frac{3}{r} (sphere)$
Smaller cells have higher SA:V — better diffusion of nutrients and wastes.
5.Mitosis Chromosome Behaviour
$2 n \to 2 n$
Mitosis: parent cell (2n) divides into two identical daughter cells (each 2n). No change in chromosome number.
6.Meiosis Chromosome Behaviour★
$2 n \to n$
Meiosis: parent cell (2n) divides into four gametes, each with n chromosomes (haploid).
7.Number of Cells after m Mitotic Divisions
$N = 2^{m}$
Starting with 1 cell, after m divisions you get 2ᵐ cells.