Biochemistry
Which of the following would have the greatest effect on the freezing point of a liter of water: the addition of 2 mol NaCl or 2 mol of glucose?
2 mol NaCl, because it will dissociate into Na and Cl and have double the impact
What other functional groups can form hydrogen bonds? Why don't CH groups participate in hydrogen bonding?
Electronegative atoms bound covalently to hydrogen can hydrogen bond, this allows carboxylic acids, amides, alcohols and amines to hydrogen bond with water. CH groups cannot participate because there is no dipole, as carbon is not electronegative relative to hydrogen.
Why is ice less dense than water?
Ice forms a hexagonal lattice to maximize the amount of hydrogen bonding, thus, ice has lower density than liquid water, and will float.
Why would a zipper or a Velcro strip be an appropriate analogy to weak interactions in biochemical reactions?
Individually, the interactions between Velcro fibers and weak interactions are easy to break(and re form) but in order to separate to things joined by many of either Velcro fibers or weak IMFs, all interactions must be severed.
How do the four types of weak intermolecular forces compare to each other and to covalent bonds?
Intermolecular forces are always weaker than covalent interactions. Induced dipole/Van Der Waals forces<Dipole-Dipole<Hydrogen<Ionic<covalent
What is the diving force behind the formation of micelles?
Micelles form due to the hydrophobic effect. Nonpolar sections of aliphatic molecules will aggregate so that fewer water molecules are ordered, increasing the entropy of the system.
Amphioathicity is important to the structure and function of which biomolecules?
Micelles, lipids, phospholipid bilayer
What physical property of oxygen could contribute to its concentration being a limiting factor for aquatic animals under water?
Nonpolar gasses like O2 dissolve poorly in water
At a pH equal to the pKa of a weak acid, what can be said about the concentrations of the acid and its conjugate base?
That they are equal
What point on a titration curve indicates the pka of a weak acid?
The midpoint
Describe what occurs when a crystalline salt dissolves in water in terms of the enthalpy and entropy of the system.
The partial charges on water can interact electrostatically with the ionic species in salt, as water molecules permeate the ions, they become less likely to interact with each other (because more space is put between them, and eventually become caged by the water molecules. Water is especially good at this because of its high dielectric constant. Entropy increases as the salt is dissolved, electrostatic interactions between the ions and water lowers the energy of the system
How are tightly bound water molecules in DNA and proteins different from "free" water molecules?
Tightly bound water molecules become "part" of the protein.They have distinctly different properties from the "bulk" water, as they are not osmotically active. They may serve crucial roles (the chain of water stuck in cytochrome f, allowing proton hopping to occur).
How do hydrogen bonds contribute to the high melting and boiling points of water?
Water has the ability to effectively hydrogen bond with itself because it can act as both a hydrogen bond donor and a hydrogen bond acceptor, allowing it to have a maximum of 4 hydrogen bonds per molecule. These bonds need energy to be broken, and need to be broken in order for a state change to occur.
What is the shape of a water molecule? How is its unequal charge distributed over the shape?
Water is a distorted tetrahedron with a strong net dipole movement, caused by the difference in electronegativity between oxygen and hydrogen.
