IUG , Faculty of Science,
Dept. of Biochemistry
Enzymes, 1st Semester,
Mid-term Exam, 6/11/2012
Answer the Following Questions
I)
Give
reasons
breively:
1)
V vs [s] of single
substrate enzyme catalysed reaction is hyperbolic
2)
Velocity is used
instad of [E] for quantitation of enzyme activity.
3)
Lactose synthase is
inactive during pregnancy.
4)
Some enzymes are
present in nature in complex form
5)
Enzyme substrate in
vivi is equal or less than Km
II)
Explain
At least
1)
3-pionts
attachment theary of enzyme-substrate binding
2)
Validity
of
M.M.
equation
3)
Kcat
of
carbonic
anhydrase is 600,000/s
III) An enzyme with a Km of 0.35 M was assayed at initial substrate
concentration of 0.003 M. By 30 sec, 3 micromole/liter of product had been
produced. How much product will be produced at
(a) 1min
(b) 2 minutes
(c) and 6 minutes ?
(e) What % of the the original sabstrate will be utilized by the time indicated?.
(f) What is its Vmax?
IV) Plot the LineWeaver of following of an enzyme catalyzed data:.
[S] in M
Vinitial in mM/min
1.67 x10-5
2.5 x10-5
3.33 x10-5
5.0 x10-5
7.0 x10-5
1.0 x10-4
1.5 x10-4
1.67 x10-4
1.05
1.54
1.98
2.86
3.78
5.00
6.67
7.15
2.0 x10-4
3.0 x10-4
8.00
10.00
a)
From
the
plot
determine: Km, Vmax.
If initial substrat
b)
concentration is 0.1 microM, what is Fes?
IUG , Faculty of Science,
Dept. of Biochemistry
Plant Biochemistry,1st Semester,
Mid-term Exam, 10/11/2012
Answer the Following Questions
I) 1- In 1939, Robert Hill discovered that chloroplasts evolve Oxygen when
illuminated in presence of ferric ion. In this process, no reduced PC or NADPH are
formed. Write the net chemical light equation of ferric ion reduction by water under
these experimental conditions.
2) Write the net stiochiometrical equation of photosynthetic light reaction assuming
no Q cycle.
II) Show scheme of the following light reaction process with indicating aim of
each
1- Q cycle
2- Cyclic electron flow of the photosynthesis.
III) State the Chemiosmotic hypothesis by Mitchell 1961 with explaining one
evidence.
IV) Explain briefly the main differences between
123456-
Chl-a and Chl-b
Antenna and rxn center
Photosynthetic system of purple bacteria and green sulfur bacteria.
Cyt f/ and Cyt b
PQ and PC
Iron sulfur proteins
IUG , Faculty of Science,
Dept. of Biochemistry
Enzymes, 1st Semester,
Final Exam, 8/1/2013 (3, 7 students, 11:30-13:30)
Answer the Following Questions
(1) Define: Kcat (T.O #) , isoenzymes, allosteric enzymes, E.U, purification
factor, % recovery (yield).
II)
Give reasons
1)
V vs [s] of allosteric
enzyme catalysed reaction is sigmoidal
2)
Velocity is used
instead of [E] for quantitation of enzyme activity in impure
preparation.
3)
Pyruvate
dehydrogenase is present in mitochonderia in complex form
4)
Kcat is not used to
describe effiency of enzyme catalysed reaction in vivo.
III)
Explain/State/Com
pare
1)
Explain
enzyme
regulation by covalent modification. Give two examples
2)
State
enzyme
clasification and type of reaction catalyzed. Why is this systematic
classification of enzymes commenly not used?
3)
Compare
between
different types of reversible inhibition with respect to changes in
Vmax and Km.
IV)
Derive: 1) Kcat/Km
less or equal than k1
2)
The rate equation of
the following enzyme catalyzed reaction
V) An pure enzyme preparation has km = 2 mM and produced 200 nmoles
product in 15 min. at 25 C.
a) How many unites of enzyme were present in the preparation.
b) Calculate S.A. of the preparation if 3 mg enzyme was present.
c) If the M.Wt of the enzyme was 600000 Dalton, calculate Kcat, C.E. and 1/Kcat
and explain their meaning.
VI) 20 microlt of crude cell free extract of enzyme preparation (1000 ml, 25
mg/ml) was catalysed a reaction at rate of 75 nmole/min. After further
purification by heat, 20 microlt of the purified enzyme fraction (200 ml, 30
mg/ml) catalysed a reaction at rate of 100 nmole/min. Calculate % recovery and
purification factor for the enzyme. Comment on the final results.
III- Given the following data
[S]µM
Vo µM/min.(-I)
3
10.4
5
14.5
10
22.5
30
33.8
90
40.5
A) Draw L.B. plot
Vo µM/min.(+I)
4.1
6.1
11.3
22.6
33.8
B) Determine Vmax , Km ,type of inhibition, and Ki if [I] is 2mM.
B) At [S] = 10 µM, and [I] = 2mM, What fraction of the enzyme molecules have a
bound substrate and a bound inhibitor?
IUG , Faculty of Science,
Dept. of Biochemistry
Plant Biochemistry,1st Semester
Final Exam, 7/1/2013 (19 female students, L407)
Answer the Following Questions
1- Account (Why ?)
1) RubisCO can amount to 50 % of the total soluble proteins in the leaves
2) the regulation of reductive and oxidative part pentose phosphate pathways
by light.
3) CO2 concentration in RubisCO side in C4 plants is higher than in C3 plants
4) Most CAM plants are succulent
5) The ratio of oxygenation to carboxylation by Rubisco in the leaves is
mostly high
2- Show without structural formula
1) the photorespiration pathway (Show the compartments)
2) Process of stomata opening
3) Principle of CAM
4) CO2 concentrating mechanism in plants of NADP-malic enzyme type
5) NADPH transport from the chloroplast to cytosol.
3- Show with structural formula
1) The reduction of 3-PG to TOP.
2) The conversion of Glucose 6-phosphate into Ribulose 5- phosphate
3) Two different transamination reactions
Extra questions
1- Compare between Cyclic and noncyclic photosynthesis
2- Show by chemical equations three different Functions of ferredoxin
3- The number of protons released by the cytochrome complex into the lumen is
doubled by Q cycle. Show the scheme.