OLM2 - pH, Amino Acids, and Peptides

Question 1

Acids

Answer 1

proton donors (increase [H+] and decrease pH)

Question 2

Bases

Answer 2

proton acceptors (decrease [H+] and increase pH)

Question 3

strong acid or base

Answer 3

ionizes completely in aqueous solution

Question 4

weak acid or base

Answer 4

does not ionize completely in aqueous solution

Question 5

dissociation constant (Ka)

Answer 5

Ionization of a weak acid (HA) is characterized by its dissociation constant (Ka).

Ka = [H+][A-]/[HA]

The value of Ka is proportional to the strength of the acid. A larger Ka means more dissociation, higher [H+], and lower pH.

A- is known as the conjugate base of the weak acid HA.

pKa = -log(Ka), analogous to pH.

Ionization of a weak base is described in the same manner using Kb and pKb.

Question 6

Henderson-Hasselbalch equation

Answer 6

pH calculations for buffer systems are performed using the Henderson-Hasselbalch equation:

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

Question 7

Bicarbonate/CO2 relationship in biological buffering

Answer 7

Bicarbonate (HCO3-) is in equilibrium with carbonic acid
and carbonic acid is in equilibrium with CO2 dissolved in the blood so CO2 effectively acts as the weak acid in this system, and HCO3- is its conjugate base.

Question 8

Acidic amino acids

Answer 8

Aspartic Acid (Asp) D
Glutamic Acid (Glu) E

Question 9

Basic amino acids

Answer 9

Lysine (Lys) K
Arginine (Arg) R
Histidine (His) H

Question 10

Polar amino acids

Answer 10

Serine (Ser) S
Threonine (Thr) T
Tyrosine (Tyr) Y
Asparagine (Asn) N
Glutamine (Gln) Q

Question 11

Non-polar amino acids

Answer 11

Glycine (Gly) G
Alanine (Ala) A
Valine (Val) V
Leucine (Leu) L
Isoleucine (Ile) I
Proline (Pro) P
Cysteine (Cys) C
Methionine (Met) M
Phenylalanine (Phe) F
Tryptophan (Trp) W