Chapter 2 - Water, Molecular Interactions, Acid-Base Flashcards Preview

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Flashcards in Chapter 2 - Water, Molecular Interactions, Acid-Base Deck (22):
0

Number of hydrogen bonds possible per water molecule

4 (2 bonding to Hs and 2 bonding to the lone pairs of O)

1

Lifetime of hydrogen bond?

1-20 ps (10^-12s)

2

Hydrogen bond donors

N-H, O-H, not C-H

3

Hydrogen bond acceptors

N: and O:

4

Hydrogen bond is stronger when 3 atoms...

Involved lie in a line

5

Difference in the energy between a functional folded protein and an unfolded protein

10kJ / mol

6

Strength of hydrophobic interactions (displacement of water)

0.4-4 kJ/mol

7

Strength of pi stacking (aromatic ring stacking)

0.4 - 4 kJ/mol

8

Strength of Van der Waals interactions (weak but many)

0.4-4 kJ/mol

9

Strength of hydrogen bond (O-H⚫️⚫️⚫️⚫️⚫️O-C)

4-40 kJ/mol

10

Strength of electrostatic (pH effects, opposites attract, likes repel)

4-40 kJ/mol

11

Strength of salt bridge (hydrogen bonding plus electrostatic)
E.g. Carboxylate amino acid side chain (Asp, Glu) to basic amino acid side chain (Arg, Lys)

40-400 kJ/mol

12

Both hydrophilic (likes water, polar or charged) and hydrophobic (dislikes water, nonpolar) is called...

Amphipathic

13

What's the equilibrium constant (Keq) for water dissociation at 25*C?

1.8 x 10 ^ -16 M

14

Ion product of water at 25*C?

Kw = [H+] [OH-] = (1.8 x 10 ^ -16 M)(55.5 M) = 1.0 x 10^-14 M^2

15

Bronsted Acid?

H+ donor

16

Consists of an aqueous solution of a weak acid (proton donor) and its conjugate base (proton acceptor)

Buffers

17

Tend to resist changes in pH, near the buffering-weak-acid pKa, when small amounts of acid (H+) or base (OH-) are added

Buffers

18

pH = pKa + log ( [A-]/[HA] )

Henderson - Hasselbalch Equation

19

A digestive enzyme secreted into gastric juice, which has a pH of ~1.5

Pepsin

20

Digestive enzyme that acts in the small intestine, and has a pH optimum that matches the neutral pH in the lumen of the small intestine

Trypsin

21

Hydrolytic enzyme thought to aid in bone mineralization

Alkaline phosphates of bone tissues