Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

First Mid-Term Exam.

Enzymes kinetics(Bioc4307)

Date: 1/11/2004

Answer the following:

1-Derive The M. M. equation by rapid equilibrium approach, integrate it in order to get a straight line equation, and plot it.

2-An enzyme with km of 2.0x10-4 M was assayed at the following substrates: 2x10-5, 6X10-4, 10-3, 2x10-2, and 0.05 M.

a)If the velocity observed at 0.05 M was 130 µM/min, calculate initial velocity at other substrate concentrations.

b)How much product will be formed from 0.05 M substrate concentration at 1, 3,5,10, and 20 min. and what percent of initial substrate concentration utilized by the time indicated?

Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

Second Mid-Term Exam.

Chemistry of proteins and lipids(Bioc4308)

Date: 27/11/2004Name:------, NO.------

Answer the following:

I-Complete the following (7pts)

1------is involved in the transfer of LCFA to mitochonderia.

2- Steps of ß-oxidation of Fatty acylCoA are:------,------, ------, and ------.

3- A very recent finding suggests that NADH gives only ---- and FADH2 gives only -----.

4- PropionylCoA produced from oxidation of odd chain

fatty acid is further metabolized into ------.

5-α-oxidation process has been found important in -----. The oxidation of fatty acid by α-process does not need neither ------nor it yields ------.

6- The net reaction of palmitate synthesis is ------

------

II-1- Write Salih Wakil’ reaction. State the name of the enzyme required, and its effectors.(3 pts)

2- In small intestine and other tissues, the trans-membrane transport of some AAs occurs by Alton Meister cycle. Show steps of the cycle and # of ATP required for one AA transported.(4 pts)

3- Show all reaction steps of urea cycle and state methods of its regulation (7 pts)

Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

Second Mid-Term Exam.

Enzymes kinetics(Bioc4307)

Date: 6/12/2004Name:------, NO.------

Answer the following:

1-Explain shortly four different evidences that support induced fit mechanism of substrate-enzyme binding.

2-Chemotyrpsin was inhibited noncompetitively in acidic condition according to the following mechanism:

a)Derive the rate equation.(5 pts)

b)Show by plotting, how you can determine Ka by two different ways.(5 pts)

3-(a) What concentration of competitive inhibitor is required to yield 75% inhibition at a substrate concentration of 1.5x10-3 M if Km = 2.9x10-4 M and Ki = 2x10-5 M?(3 pts)

(b) To what concentration must the substrate be increased to reestablish the velocity at the original uninhibited value?(3 pts)

V)For a mono-substrate catalyzed rxn, the following data were obtained (16 pts)

Time(min)Substrate conc. in mM

0 0.5011

30 0.4511

60 0.4038

90 0.3626

130 0.3148

180 0.267

and determine /k and t1/2 .

2) How long will it take to hydrolyze 90 % of the substrate initially present?

3-Names of two enzymes that are monomeric and not proteases.

4-Induced fit hypothesis by Koshland,1958 and 4-different evidences.

Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

Final Exam.

Enzymes kinetics(Bioc4307)

Date: 4/1/2005Name and #:------Time: 1.5 hrs

I-State(5pts)

1- Three types of enzymes specificity.

2-Two examples about substrate inhibition.

II-Complete the following (10 pts)

1- Km =----- when Vo = ----.

2- NAD+(or NADP+) dependent dehydrogenases are assayed at -----

3- C.E.= ------≤ ------.

4-Fes =------= ------.

5-Katal =------.

6-Purification factor =------

7- % Yield (recovery) =------

8- [S] phys.≤ ----

III)(12 pts)

1- Show the suitable plot that distinguish between NCI and Irreversible inhibition (show slope values).

2-Starting from M.M. equation, prove that Ln[S]0/[S] = /K t

3)According to your knowledge about first order kinetics, show plots of V v.s.t, [S] v.s. t, and [P] v.s. t.

IV)(8 pts)

1-The substrate of an enzyme must be deprotonated (pKa of the ionizable group = 4.5). The active site of the enzyme contains a histidine residue (pKa = 6.5) that must be protonated for activity to occur. What is the pH optimum of the reaction?

2- If an enzyme has a specific activity of 120 U/mg protein.

a)Calculate the T.O.# if M.W.of the enzyme is 360,000 (explain the answer).

b)Calculate the time required for one catalytic cycle(explain the answer).

V- Close proximity of one enzyme to another in the Pyrovate dehydrogenase complex increases the overall rxn rate and minimizes the side rxns. Explain the mechanism of rxn catalyzed by the complex showing the role of each enzyme component and the role of the 5 different coenzymes involved (10 pts).

VI) Ask your self a question about a mechanism of action of a coenzyme and answer it. (6 pts)

Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

Final Exam.

Chemistry of proteins and lipids(Bioc4308)

Date:6/1 /2005Name & NO.------Time: 2 hrs

Answer the following:

I-Complete the following biochemical reactions(do not name required enzymes).

(5 pts)

- Asp + NH3→

- Glu + Pyr →

- Glu → NH3 +

- CO2 + NH3 + H2O + 3 ATP + ASP→

II) Prepare(show enzymes and structures required):

(13 pts)

- α-K.A. from D-AA

- Ser. from 3-PG

- Oleic acid from palmitic acid.(6 pts)

III) Compare between Cahill Cycle and Cori cycle (with respect of the mechanism and the condition of occurrence)(6 pts)

IV)Adipose tissues utilize excess glucose for TAG biosynthesis. In other words, excess glucose intake causes obesity. Discuss by using suitable scheme.(6 pts).

V)1- Calculate # of ATP produced from complete oxidation of Oleic acid.(4 pts)

2- De NOVO synthesis of fatty acids is catalysed by AcetylCoA carboxylase and multi-enzyme complex. According to your knowledge, write the rxns catalyzed by each enzyme of the complex: (12 pts)

a- MT

b-AT

c-CE

d-KR

e-DH

f-ER

VI) Ask you a question and answer it.(6 pts)

VII) Starting from Heme in spleen, Show step by step how SBG and UBG appear in urine and feces (name intermediates without structure and enzymes required).(8 pts)

Faculty of Science, IUG

Dept. of Chemistry and Biochemistry

First Mid-Term Exam.

Biochemistry of hormones(Bioc4204)

Date: 19/4/2005Name:------, NO.------

======

Answer the following:

I) Complete the following table (4pts)

HormoneName of cell by which synthesized

Glucagon------

Insulin------

Somatostatin------

GH------

Prolactin------

Tropic Hormones ------

II) Calculate the osmolarity and osmotic pressure of NS (R = 0.082 Lt-atm/mol-deg, T = 37 0C).(4 pts)

III- Glucagon is an antigonist of insulin action

1)Show the metabolic role of insulin and glucagon in carbohydrates and lipids metabolism in liver (6 pts)

Insulin

(+)(-)

carbohydrates Metabolism

Fats metabolism

Glucagon

(+)(-)

Carbohydrates Metabolism

Fats metabolism

2) Explain the mechanism of action of both hormones, showing the antigonist relationship.(6pts)

IV- Why? (8pts)

1) low blood volume stimulates ADH secretion more than low blood osmolarity.

2) Hyperglycemia still occurs after pancreactomy in spite of presence of IGFs which their functions are similar to insulin.

V) Prove (12 pts).

1)GH plays a major rule in growth.

2)G.I. hormones stimulate insulin secretion.

3)A patient has a neurogenic D.I.