General Biology: Biochemistry, Microbiology and Immunology formula sheet

Ratio of deprotonated (A-) to protonated (HA) form of one ionisable group, with pKa = -log10 Ka. At pH = pKa the two forms are equal, and a group buffers best within about 1 pH unit of its pKa.

pK1 is the alpha-COOH and pK2 the alpha-NH3+. For any amino acid, pI is the average of the two pKa values that lie on either side of the neutral (net charge zero) form.

R = 8.315 J/(mol·K); RT ≈ 2.48 kJ/mol at 25 °C. Q is the mass-action ratio [products]/[reactants]; at equilibrium Q = K'eq and ΔG = 0.

K'eq is the equilibrium constant at pH 7. Each tenfold change in K'eq changes ΔG°' by about 5.7 kJ/mol at 25 °C (this is RT ln 10).

Initial velocity of a single-substrate enzyme under steady state with $[S]\gg [E{]}_T$. $K_m$ is in concentration units (mM or $\mu$M), $V_{max}$ in concentration per time (for example $\mu$M/min).

For $E+S\underset{k_{-1}}{\stackrel{k_1}{\rightleftharpoons }}ES\stackrel{k_2}{\to }E+P$. $K_m$ equals the substrate concentration at which $v=V_{max}/2$. It equals the dissociation constant $K_d=k_{-1}/k_1$ of ES only if $k_2\ll k_{-1}$.

$N_0$ is the initial count and $N_t$ the survivors after time $t$ at one fixed temperature; $D$ is in the same unit as $t$. Valid while the death curve is a straight line on a log scale.

$D_{T_1}$ and $D_{T_2}$ are the D-values at temperatures $T_1$ and $T_2$ ($T_2>T_1$); $z$ is in the same temperature unit.

Convention: 2 ATP hydrolysed per electron transferred; 8 electrons per N₂ (6 to make 2 NH₃ and 2 for the obligatory H₂), so 16 ATP per N₂. In cells the cost is often higher because extra H₂ is made.

Use a plate with a countable number of plaques (conventionally 30 to 300). The dilution is the fraction of the original stock in the plated sample (such as $10^{-6}$).

Each cleaves C3 into C3a (anaphylatoxin) and C3b (opsonin); C3b joining the convertase makes the C5 convertase.

Common to all pathways. The MAC is a pore that lyses Gram-negative bacteria and other susceptible cells.

Applies when the two parents carry four different haplotypes between them and there is no recombination within the MHC. Each child receives one of two maternal and one of two paternal haplotypes, each with probability 1/2.

$R_0$ is the basic reproduction number and $E$ is vaccine efficacy (fraction, 0 to 1). $1-1/R_0$ is the herd immunity threshold, the coverage needed when $E=1$. Assumes homogeneous mixing, and applies when $E$ is high enough that $p_c$ does not exceed 1.