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Chemistry 256
Exam 2-50 pts (3/23/16)
1. (2 pts) What molecule(s) are/is instrumental in transferring the amino group from
amino acids to the Urea cycle?
a. Glucose
@ Pryidoxal-5-phosphate (PLP)
c. ATP
@} a- ketoglutarate
e. Glutamine
(2 pts) What organelle contains hydrolytic enzymes that breakdown proteins within
a cell?
2.
a. Aminotransferease
®Lysosome
c. Protease
d. Mitochondria
e. Dehydrogenase
3· (8 pts) The 6 events listed below occur during photosynthesis. List the order of events
(#1 first-#6last)
·
_2.__ An Electron is extracted from water and 02 is produced
_Y_ NADPH is produced
_ _ Chlorophyll absorbs sunlight in the PS II complex
3 A proton gradient is produced across the thylakoid membrane
_S_ C02 is 'Fixed' in the Calvin cycle
h
GAP is produced
4. (2 pts) Circle all that are true about the protein ubiquitin;
a. Is a catalyst in protein biosynthesis
@ 'Marks' proteins for degradation
c. Is active only at pH 5 and below
@> Involves a thioester formation with a 'conjugating enzyme'.
e. It transfers an amino group to Urea.
5. (3 pts) What is the fate of the amino acid alanine (below) when it is degraded?
0
II
H2N-CH-· C-OH
I
CH3
G)
b.
~~
\£.1
d.
e.
The NH3 group is incorporated into the Urea molecule
o •
The NH3 group is converted to N2
II,,
e
The carbon skeleton is converted to Pyruvate
cr•3 - c:. ~e-2>
The carbon skeleton is converted to Urea
The carbon skeleton is converted to Acetone
6. (6 pts) For the places/events listed below, state whether it is associated with
photosystem I, photosystem II or both.
__f_s_.n:__ The Oxygen Evolving Center
__t'_S_l.
__NADPH production
_?_s_JL_ _Proton gradient generation
J
_f_s_1I.
_ _.ATP synthesis
_"6_c:._~~_ _.Absorption of a photon to an excited state
_s_b*'
___Cytochrome b6f complex
7. (2 pts) In which part of the chloroplast do the 'light reactions' take place?
@ Thylakoid membrane
b.
c.
d.
e.
Stroma
Outer membrane
Inner membrane
Chloroplast center Hub
8. a (5 pts) Fill in the missing reactant and product of the transamination reaction
below.
Reactant
~I(/o-
+
HOCH{"'"
+Product
0
~
~~3.
\
g
~0 tt-\"1- --c.~
'1(0
b
( S e.r •1'\A.")
b. (2 pts) The PLP is an important cofactor in the reaction above. Circle the compound
below that is ·PLP.
H
PO
PO
PO
c. (2 pts) Describe the role of the PLP co-factor in the aminotransferase reaction?
e.a"(-f\~l ~ N~~ e~
N&-v\
+~ A~ ~"'... tv ..Vls-~~ fil'\lo,.-p,.r~-&r- rf I~ .J.,..
~ luhslv~YA-bz
d. (3 pts) Draw the structure ofPLP after 'stage 1' of the 2 stage process of
transamination.
"'
L 1""o.\ec.. ~ -tf-..., +k A-A
3
.,."'\'\~
®o~o"
~~()\)
)\
9. (2 pts) What statement(s) are true regarding Nitrogen Fixation (circle all that are
true):
a. Nitrogen fixing occurs during photosynthesis ¢>
@ Nitrogen fixation is energetically costly _,.1.\c;.. s '
@ Is the conversion of Nitrogen Gas (N2) to Ammonia (NH 3)
d. Occurs in the Calvin cycle
@ Is essential for amino acid production in plants.
a. (2 pts) What are the 2 major products of the photosynthetic reaction centers PSI
and PSII?
10.
b.
(2
~
pts) What process do these 2 products feed into?
Nitrogen fixing
1
(]1 Calvin cycle - 'D"'r'L
Qtac.-h£'1')~
1
c) Urea cycle
d) Electron Transport chain
e) Citric acid cycle
pts) A product of the 'dark reactions' is glyceraldehyde-3-phosphate (GAP). What
are the final products that GAP will go onto produce?
11. (2
GAf _... c""~ l::.bh~c:l~l.u /s"J"'r!>
12.
PAH is an enzyme that catalyzes the transformation of Phenylalanine to tyrosine
0
OH
OH
PAH
HO
Tyrosine
Phenylalanine
a. (2 pts) Circle what is true below considering that Insulin inhibits the activity of PAH
while glucagon stimulatesJthe activity of the enzyme.
IS
().t.h'-''- \.,
PAH is phosphorylated in the presence of glucagon
PAH is deactivated in the presence of insulin
Glucagon will promote phenylalanine degradation to form gluconeogenesis
products.
d) Glucagon will promote phenylalanine degradation to form Fatty acid products.
b. (3 pts ) Phenylketorurea (PKU) is a disease where there is a deficiency of the enzyme
PAH that converts phenylalanine to Tyrosine. When phenylalanine cannot be converted
to Tyrosine what is its fate (show the reaction)?