Chem 464 Spring 2017
Section: Abrol
Page 3of10
ExamC
Wednesday, 19 April 2017
Problem 1 (14 Points)
lA. (2 points) When the linear form of glucose cyclizes, the product is a(n):
a) anhydride.
b) glycoside.
@ hemiacetal.
d) lactone.
e) oligosaccharide.
lB. (3
a)
b)
c)
points) When forming the disaccharide trehalose from two glucose monosaccharides:
water is eliminated.
H
a hemiacetal is converted to an acetal.
the resulting dissacharide is no longer a reducing
sugar.
jl Both a) and b).
Trehalose
(.:D All ofa), b), and c) above.
a-o-glucopyranosyl a-o-glucopyranoside
Glc(al - 1a)Glc
lC. (3 points) Which ohe of the following statements about hydrogen bonding in glycogen and
cellulose is true?
a) Glycogen forms more internal H-bonds than cellulose.
b) Extensive internal hydrogen bonding makes cellulose
more water soluble than glycogen.
c) Extensive hydrogen bonding with water makes
cellulose more soluble than glycogen.
HO
0
Glycogen primarily forms hydrogen bonds within a
HO
HDH C
single chain.
_o
e) The hydrogen bonding in cellulose favors a helical
Starch and Glycogen
(a-1,4 linkages)
conformation.
H:~~OH2
@
2
-/f
lD. (3 points) Which of the following is not true of all naturally occurring DNA?
J!2.. Deoxyribose units are connected by 3 ',5 '-phosphodiester bonds.
\£)) The amount of A always equals the amount of T on the same strand.
c) The ratio (A+T)/(G+C) is not constant for all natural DNAs.
d) The two complementary strands are antiparallel.
e) Two hydrogen bonds form between A and T.
lE. (3 points) Which of the following are possible base compositions for single-stranded RNA?
a)
b).
..£1..
~
e)
%A
%G
%C
%T
5
45
45
0
25
25
25
0
35
10
30
0
All of the a), b), and c).
Both a) and b).
%U
5
25
25
DH
o,
...,
Chem 464 Spring 2017
Section: Abrol
Page 4of10
ExamC
Wednesday, 19 April 2017
Problem 2 (20 Points)
2A. (3
a)
b)
c)
points) Identify the molecule(s) derived from sterols.
Arachidonic acid
Vitamin A
Phosphatidylglycerol
~ Prostaglandins
(:V Estrogen
2B. (4 points) Draw the structure of any triacylglycerol.
0
// ~ ,/\\."'-<'/'-..._'-..//
0 -c:
/
~ ............
c \:.-\i\
~ /-=="\. /'\.
c.~ " V - V "-
\\ '
C \-\-0/
.
I
c ~l-
"o-c/
\
0
or
or
or
2D. (3 points) Which one of these is a general feature of the lipid bilayer in all biological
membranes?
@ Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.
b) Lipid rafts are comprised of lipids from only one leaflet of the lipid bilayer.
c) Polar, but uncharged, compounds readily diffuse across the bilayer.
d) The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.
e) The polar head groups face inward toward the inside of the bilayer.
2E. (4 points) When a bacterium such as E. coli is shifted from a warmer growth temperature to
a cooler growth temperature, it compensates by:
a) increasing its metabolic rate to generate more heat.
b putting longer-chain fatty acids into its membranes.
putting more unsaturated fatty acids into its membranes.
) shifting from aerobic to anaerobic metabolism.
e) synthesizing thicker membranes to insulate the cell.
Provide a reasoning for your choice.
To pre.ivtM)r
~-rt., K-\~J. ~b"'<n'V\~
.:IA coo\~ i-e-~f-ex'~e.,,
[_ e..o\~ w\\\ ~ \N'-0~ u~s.~ ~ OLt.A~ 'fv
!h yv\.Byv'\ ~'A't, '~ ~ ~~ +l~~ble., ~ Jct~\'YV(i(_.
Chem 464 Spring 2017
Section: Abrol
Page 5of10
ExamC
Wednesday, 19 April 2017
Problem 3 (14 points)
3A. (8 points) Draw the structures of both anomers of fructose in the furanose ring form and
name them.
\.lO~Cl-4~
O
C"i..D~
»
H
HO
0 \-\0 \.\
H
3B. (4 points) How many chiral carbons does each of these structures have?
.
""
\
0( - a~ ~- ( s \
I
t'\o\C.-W,. .
3C. (2 points) How many stereoisomers of fructose are theoretically possible in the furanose
ring form?
2
+
Chem 464 Spring 2017
Section: Abrol
Page 6of10
ExamC
Wednesday, 19 April 2017
Problem 4 (12 points)
4A. (7 points) The number of structurally different polysaccharides that can be made with 20
different monosaccharides is far greater than the number of different polypeptides that can be
made with 20 different amino acids if both polymers contain an equal number (say 10) of total
residues. Explain why. Draw a reasonable structural representation to support your explanation.
MoV\o ~o__c,c.,he.:nk
~v-.-o
CLUc\
exa.~ ·.
e;x:o-~~ -:.
0
N-0-C...
rol1r~\-\k t=?l<:o.~\..t. ·.
N . -Oc...c- ~-o-c- "'-0-c.- N-0~ c.- N
c..v-.
.
·- 6-c.. - '' ~ .. .
~'G-- "=--e. jJ "'~'\. :v-t- ~ rt)1!~~ pe ~$.~~\~ ...
4B. (5 points) Mouse DNA hybridizes more extensively with human DNA than with yeast DNA.
Explain by describing the factor or factors that dete1mine extent of hybridization.
s:
s; \on~
hM)'V'1).-
°\-
D )
~ 1> ~ Pr
'D ,~ pr- ~ h-a ~ "
\02-0
Chem 464 Spring 2017
Section: Abrol
ExamC
Wednesday, 19 April 2017
Page 7of10
Problem S (17 points)
SA. (S+3 points) y-Linolenic Acid (GLA) is a fatty acid with the name all-cis-6,9,12octadecatrienoic acid. Draw its structure. Write its name in the ~ nomenclature [e.g., in the
format 15: 1(~ 9 )] .
. w - e..v-.J
12..
SB. (3 points) Is this fatty acid an ro-3 fatty acid? Is it an ro-6 fatty acid? Explain briefly.
1:-t '~ no+
b~ a±
0.'1
t-0 -
3 ·~ o...c.) cA
o.o - ~ e. ~ ~
\s
Yl-o
cl..n ~
w-3 ~CM(*-). J:+
~,~, t..u~~ -~ ~c....:· ~
be.c_a..u.o~ -~ c<:. Cl\ ~le Jc:,~ a)- w-6 GvJ,o--.-, (©) .
SC. (6 points) Order the following molecules in terms of the ease by which they can diffuse
across the cell membrane. Provide an explanation for your ordering.
I.
H20
II.
Alanine amino acid
III.
Lysine amino acid
IV.
V.
Phenylalanine amino acid
Glucose
R~~
~~
~~
l~
io
~
J)r~
~~~
~C:tT>vY> .
M~
Ne,~ b~ po~ rvwle~ c.e....._ )J.' ~e. ~"''C,
tte~
~~
·f4i-...
h~ -i.w1\~~~'c.. ervve-:, ) ~cJ- c-- dJ ~-e. ~e., ~
~~ ~e..,. \+;.,o Is ~~ ~c.~~ ,~ ~l~~~- F 1~ ~ol°"' ~v-. A- .
Chem 464 Spring 2017
Section: Abrol
Page 9of10
ExamC
Wednesday, 19 April 2017
Problem 7 (Extra Credit 5 points)
Remember the biochemist Dr. Lorba from previous extra credit problems? His long note talked
. about the nucleic acids in the pre-historic life, which also comprised of four bases: A, T, C, and
G, that utilized Watson-Crick pairing. However, the major difference between these nucleic
acids and modem ones was that these bases combined as doublets instead of triplets to code for
specific amino acids. So, for example, the AT combination was one doublet codon that coded for
a specific amino acid.
7A. If one of the doublet codons was used as a start codon, how many maximum amino acids
could be possibly coded by these prehistoric nucleic acids?
Mo..y.;~""'.'I
AA~ AIJ AC/ A-~
·-rA, \1.,
Tc 11 G.,
CA-, C},
cc_)
CC-,
GiA, ~T , G-iC > Gi
Ci
AAs. ~ QAv-. to-~
CQ~~ ~~l6 ..
w-tt~ 1 3~ C.t)~ &.- l ~t
l4- .
7B. In reality, the number of amino acids observed were about half of that maximum number.
What could be a reasonable explanation for this observation?
~~""'
~""'- b-e
'\p C;S s ~ ldk ?
°'" c.l ~ ~ --\-o tG~ ~ .cJJo.V\.ua ; '-c...s cli~ ~cko~ s.'VV\ ~ ~ \\}~\?))\~ (~.