2.1 the properties of water
ionic(electrolyte) and polar(-OH,,hydrogen bonding.) substances dissolve in water(hydrophilic)
non polar substance are insoluble in water(hydrophobic)
O—H….O 在一條直線上
有一對lone pair就可以連一個氫鍵，所以O可以連兩個，雙鍵O可以連一個
一個水分子4個氫鍵，但兩兩共用，所以1mol水有2mol氫鍵。
冰中水分子間的距離更小所以氫鍵能量更大。
the hydrophobic effect is critical for the folding of proteins and the self-assembly of biological membranes.
detergents: amphipathic substances 兩性物質 Osmotic Pressure 滲透壓
2.2 weak interactions in aqueous systems
4 major non covalent bonds(forces) in biomolecules:
a. electrostatic interactions: charge-charge interactions, hydrogen bonds, van der waals forces.
b. hydrophobic interactions.
偶極矩的單位為D( Debye德拜), 方向用+->表示，從正到負，指向電子云密度高的一方。
而電子對轉移箭頭則是從帶負電的nucleophile（Nu-）一端到正電。
2.3 ionization of water, weak acids and weak bases
1g/cm^3 = 1000/18 = 55.5 mol/L
water: k_eq = [H][OH]/55.5M = 1.810^-16 \therefore k_w = [H][OH] = 110^-14 M^2
weak acids(a.a.) and weak bases(purines, pyrimidines):
k_a = [H][A]/[HA] , k_b = [HA][OH]/[A]
0.01, 0, 0 —> 0.01-X , X, X [X]^2/[0.01-X] ~= [X]^2/0.01 (原弱酸濃度基本不變)
Henderson-Hasselbach Equation: pH = pKa + log([A]/[HA])
the titration curve (將堿加入為[HA]的一半，這樣生成的[A]和剩下的[HA]就一樣多了)
2.4 buffers and buffered solutions resist changes in pH
buffer: a weak conjugate acid-base pair
working pH range: pH = pKa +/- 1
blood 7.4: H2CO3— HCO3-
cytoplasm of all cells: HPO_4^2- — H_2PO_4^-
buffer preparation: 給出pKa, 配一定pH的buffer, 可以先用hhe求出[A^-][HA]堿酸濃度比，再根據題中所給的兩物質各自的濃度和總體積，求出各物質的體積。
