ACS BIOCHEMISTRY PRACTICE FINAL,
FGCU, BEHARRY, COTICONE WITH
COMPLETE SOLUTIONS {GRADED A+}
1. A weak acid, HA, has a pKa of 4.11.
a) At pH 7.11, what will the ratio of conjugate base to acid be?
(Henderson-Hasselbach equation: pH=pKa + log [A-]/[HA])
b) Based on answer to "a," is there more HA or A- at that pH?
c) At pH 2.11, what will the ratio of conjugate base to acid be?
d) Based on answer to "c," is there more HA or A- at that pH?
e) At pH 4.11, what will the ratio of conjugate base to acid be?
f) Fill in the blank: if pH is greater than the pKa of a weak acid, there will be
___ A- relative to HA. If the pH is less that the pKa of a weak acid, there
will be __ A- relative to HA. If the pH=pKa, there will be ___ of A- and HA. -
✔✔ a) 7.11=4.11+log[x]
3=log[x]
1000=x
,b) A-
c) 2.11=4.11+log[x]
-2=log[x]
0.01=x
d) HA
e) 1
f) more; less; the same amount
2.
a) Which amino acids would be charged at pH 7?
b) which amino acids from "a" would be negatively charged?
c) which amino acids from "a" would be positively charged? -✔✔ a) Asp,
Glu, Arg, His, Lys
b) Asp, Glu
c) Arg, His, Lys
3. Which of the following sequences is most likely to be in the interior core
of a globular protein? Why?
a) ITFWLI
b) IKFGVA
c) DKYPGE
, d) MPCDNA -✔✔ A; because no charged amino acids and highest % of
nonpolar
4. How are beta sheets stabilized in proteins? -✔✔ Hydrogen bonding
between peptide backbone groups?
5. Compare fibroud proteins such as keratin and globular proteins:
a) Water solubility
b) flexible secondary structure
c) highly repetitive primary structure
d) size and ability to associate into larger structures -✔✔ a) fibrous:
insoluble
globular: soluble
b) fibrous: no
globular: yes
c) fibrous: yes
globular: not necessarily
d) fibrous: elongated structrue; two alpha keratin polypeptides, each of
which form an alpha helix, twisting around each other to form a left-handed
coil
globular: varies
FGCU, BEHARRY, COTICONE WITH
COMPLETE SOLUTIONS {GRADED A+}
1. A weak acid, HA, has a pKa of 4.11.
a) At pH 7.11, what will the ratio of conjugate base to acid be?
(Henderson-Hasselbach equation: pH=pKa + log [A-]/[HA])
b) Based on answer to "a," is there more HA or A- at that pH?
c) At pH 2.11, what will the ratio of conjugate base to acid be?
d) Based on answer to "c," is there more HA or A- at that pH?
e) At pH 4.11, what will the ratio of conjugate base to acid be?
f) Fill in the blank: if pH is greater than the pKa of a weak acid, there will be
___ A- relative to HA. If the pH is less that the pKa of a weak acid, there
will be __ A- relative to HA. If the pH=pKa, there will be ___ of A- and HA. -
✔✔ a) 7.11=4.11+log[x]
3=log[x]
1000=x
,b) A-
c) 2.11=4.11+log[x]
-2=log[x]
0.01=x
d) HA
e) 1
f) more; less; the same amount
2.
a) Which amino acids would be charged at pH 7?
b) which amino acids from "a" would be negatively charged?
c) which amino acids from "a" would be positively charged? -✔✔ a) Asp,
Glu, Arg, His, Lys
b) Asp, Glu
c) Arg, His, Lys
3. Which of the following sequences is most likely to be in the interior core
of a globular protein? Why?
a) ITFWLI
b) IKFGVA
c) DKYPGE
, d) MPCDNA -✔✔ A; because no charged amino acids and highest % of
nonpolar
4. How are beta sheets stabilized in proteins? -✔✔ Hydrogen bonding
between peptide backbone groups?
5. Compare fibroud proteins such as keratin and globular proteins:
a) Water solubility
b) flexible secondary structure
c) highly repetitive primary structure
d) size and ability to associate into larger structures -✔✔ a) fibrous:
insoluble
globular: soluble
b) fibrous: no
globular: yes
c) fibrous: yes
globular: not necessarily
d) fibrous: elongated structrue; two alpha keratin polypeptides, each of
which form an alpha helix, twisting around each other to form a left-handed
coil
globular: varies
