Chapter 2: Water, the Solvent of Life Flashcards
What is a hydrogen bond?
A hydrogen bond is a weak interaction that occurs when a hydrogen atom covalently bonded to an electronegative atom (nitrogen, oxygen or fluorine) is attracted to another electronegative atom.
Which molecules can participate in hydrogen bonding?
Molecules containing -OH, -NH, and -C=O groups can participate in hydrogen bonding due to the presence of highly electronegative atoms like oxygen and nitrogen.
Is the dissolution of hydrophilic solutes energetically favorable? Why?
Yes, because the hydrophilic solutes form hydrogen bonds with water, reducing the free energy of the system and making the dissolution process exergonic.
What happens when amphipathic molecules are dissolved in water?
Amphipathic molecules form structures like micelles or bilayer were hydrophobic tails are sequestered away from water, while hydrophobic heads face the water. Hydrophobic effect
What are the four types of weak/noncovalent interactions in biological molecules?
Hydrogen bonds: Between polar molecules
Ionic interactions: Between charged groups
Hydrophobic interactions: Between nonpolar molecules
van der Waals interactions: Weak attractions due to temporary dipoles
What is the ionization constant of water (Kw)?
The ionization constant of water Kw is 1.0 x 10^{-14} at 25°C, representing the product of [H^+] and [OH^-] .
How is pH calculated?
pH = -log [H+]
What is the acid dissociation constant (Ka) and pKa?
Ka: A measure of the strength of an acid in solution, representing the equilibrium constant for acid dissociation
pKa: The negative logarithm of Ka, indicating the acid’s strength. Lower pKa values mean stronger acid
What is the Henderson-Hasselbalch equation?
pH = pKa + log([A-]/[HA])
The equation relates pH, pKa, and the ratio of the concentrations of the conjugate base to the acid
