500 Appendix B. Numerical values[[Student version, January 17, 2003]]
Conductivity of squid axoplasmκ≈ 3 Ω−^1 m−^1
Brain:
Powerconsumption 10W(about 10% of whole-body resting total).
1013 cells in human body, of which 10^11 nerve cells.
6 · 1013 synapses.
1016 synaptic events/second, or 10−^15 J=2. 5 · 105 kBTrperevent(compare supercom-
puter, 10^6 W)/(10^15 opss−^1 =10−^9 Jperoperation).Miscellaneous
Acceleration of gravity at Earth’s surface,g=9. 8 ms−^1.
Viscosity of water at 20◦C,1. 00 · 10 −^3 Pa·s;ofair, 1. 72 · 10 −^5 Pa·s;ofhoney, 0.1Pa·s;
of glycerol, 1.4Pa·s.The effective viscosity of cell cytoplasm depends on the size of
the object considered: For molecules smaller than 1nmit’s similar to that of water;
for particles of diameter 6nm(such as a 10^5 gmole−^1 protein) it’s about 3 times
greater. For 50–500nmparticles it’s 30–300 times as great as water, while the entire
cell behaves as though its viscosity were a million times as great as water.
Viscous critical force for water, 10−^9 N,ofair, 2· 10 −^10 N;ofglycerine, 10−^3 N.
Typical acceleration in an ultracentrifuge, 3· 106 ms−^2.
pHvalues:Human blood, 7.35–7.45; human stomach contents, 1.0–3.0; lemons, 2.2–2.4,
drinking water, 6.5–8.0. Ion product of water at room temperature, 10−^14.
pKvalues:Dissociation of acetic acid, 4.76; of phosphoric acid, 2.15. Deprotonation of
aspartic acid, 4.4; of glutamic acid, 4.3; of histidine, 6.5; of cysteine, 8.3; of tyrosine,
10.0; of lysine, 11.0; arginine, 12; of serine,> 13 .0.