Chapter 2

Question 1

Describe the 7 types of non-covalent interactions and order them based on their relative strength. (highest –> lowest)

Answer 1

1. Hydrogen bonds
2. Charge - Charge
3. Charge - Dipole
4. Dipole - Dipole
5. Charge-induced dipole
6. Dipole-induced dipole
7. Van der Waals

Question 2

Which bonds are electrostatic in nature?

Answer 2

All non-covalent bonds

Question 3

Strongest hydrogen bond:

Answer 3

H bond formed in water (Covalent bond to water and non-covalent bond to water)

Question 4

“Electrostatic interaction” also means:

Answer 4

Charge-charge

Question 5

Simplest charge-charge interaction (2 ions):

Answer 5

Salt bridge
ex. NaCl

Question 6

Coulomb’s Law is used for

Answer 6

charge-charge interactions

Question 7

When we have polar molecules we have….

Answer 7

dipole and induced dipole interactions

Question 8

List these strongest to weakest:
1. Dipole-dipole
2. Dipole induced-dipole
3. Charge-charge
4. Van der Waals
5. Charge-dipole

Answer 8

3, 5, 1, 2, 4

Question 9

Hydrophobic molecules ______ to be incased in by a _________.

Answer 9

aggregate, single water cage

Question 10

A protein is ______ when the pH is greater then the pI.

Answer 10

Negatively charged

Question 11

A protein is ______ when the pH is less than the pI.

Answer 11

Positively charged

Question 12

What is the protein’s charge?
pI = 8
pH = 3

Answer 12

Positive

Question 13

Dispersion forces are formed from an ______ between two molecules with _______.

Answer 13

attraction, no permanent dipole moment or charge

Question 14

Why is water unique? (5)

Answer 14

1. it has 2 H donor sites and 2 H bond acceptor sites
2. permanent dipole
3. high heat capacity
4. greater density (m/v) as a liquid vs a solid
5. relatively high dielectric constant

Question 15

What is a dielectric constant?

Answer 15

ability to store electrical energy

Question 16

Dynamic exchange:

Answer 16

when a molecule breaks internal hydrogen bonds to form bonds with water

Question 17

Which of the following will cause the energy required to separate a charge-charge interaction to decrease?

a. Decrease the distance between the particles
b. Increase the charge of the particles.
c. Increase the dielectric constant.
d Increase the volume of the solvent

Answer 17

c. Increase the dielectric constant

Question 18

Hydration shells are to _______
Clathrate structures are to ________

Answer 18

Hydrophilic molecules
Hydrophobic molecules

Question 19

The hydrophobic effect is primarily driven by:

Answer 19

an increase in entropy of water molecules when hydrophobic molecules aggregate

Question 20

Amphipathic molecules:

Answer 20

substances that are both hydrophilic and hydrophobic

Question 21

Acids are…

Answer 21

proton donors

Question 22

Bases are…

Answer 22

proton acceptors

Question 23

Autoionization of water:

Answer 23

H2O → H+ + OH-

Question 24

pH equation:

Answer 24

pH = -log[H+]

Question 25

lower pH = higher pH =

Answer 25

acidic, + charge on a protein basic, - charge on a protein

Question 26

Isoelectric point (pI)

Answer 26

the pH when the molecule has a net 0 charge

Question 27

Disassociation is measured by: ___ Larger ____ = _________

Answer 27

Ka stronger acid

Question 28

pH = pOH = pH + pOH =

Answer 28

= -log [H+] = -log [OH-] = 14

Question 29

Henderson-Hasselbalch:

Answer 29

pH = pKa + log [A-]/[HA] [A] : conjugate base [HA] : conjugate acid

Question 30

pH < pKa → pH > pKa → pH = pKa →

Answer 30

--> [HA] > [A-] --> [HA] < [A-] --> [HA] = [A-]