Keys and analysis practical lesson 1 simple proteins. Structure and function

ANALYSIS

IIIa. A neutral amino acid exists in its zwitterionic form (no net charge) at its isoelectric point, which is pH=6. At low pH=2, the carboxylate anion is protonated and the amino acid has a net positive (+1) charge. At high pH=10 the ammonium cation loses a proton and the amino acid has a net negative (-1) charge.

KEYS

1.A. The peptide bond has a partial double- bond character. Unlike its component – the α- amino and α- carboxyl group- the components of the peptide bond do not accept or give off protons. The peptide bond is not cleaved by organic solvents or urea, but is labile to strong acids. It is usually in the trans configuration.

2.D. In proteins found in aqueous solutions, the side chains of the nonpolar amino acids such isoleucine, tend to cluster together in the interior of the protein. Glutamine contains an amide in its side chain. Serine and threonine contain a hydroxyl group in their side chain. Cysteine can form disulfide bonds. Glycine contains the smallest side chain.

3.C. Glutamine contains two titrateable groups, α- carboxyl and α-amino. Glutamine is a polar, neutral amino acid that shows little electrophoretic migration at the pH7,0. The symbol for glutamine is “Q”.

4.D.

5.C.

6.D.

7.B.

8.C.

9.D.

10.E

Practical lesson 2 physical and chemical propeties of proteins

1.E

2.C

3.D

4.E. The correct folding of a protein is guided by specific interactions among the side chain of the amino acid residues of a polypeptide chain. The two cysteine residues that react to form the disulfide bond may be a great distance apart in the primary structure (or an separate polypeptides), but are brought into close proximity by the three-dimensional folding of the polypeptide chain. Denaturation may either be reversible or irreversible. Quaternary structure requires more than one polypeptide chain. These chains associate through noncovalent interactions.

5.D

6.B

7.E

8.A

9.A

10.B

Practical lesson 3

ENZYMES. STRUCTURE AND GENERAL PROPERTIES OF ENZYMES

1. E.

2. E

3. B

4. D

5. C

6. B

7. C

8. B

9. A

10. E

Practical lesson 4 mechanism of enzyme action. Regulation of enzyme activity

1.A

2. C

3. D

4.E

5.E

6.A. In the presence of a competitive inhibitor, an enzyme appears to have a lower affinity for substrate, but as the substrate level is increased, the observed velocity approaches V max.

7.D. Km has the dimensions of concentration and is a characteristic of an enzyme under a given set of reaction conditions. Km does not depend on the concentration of enzyme, but can vary with pH. A noncompetitive inhibitor decreases V max but does not alter Km.

8.E

9.E

10.A

PRACTICAL LESSON 5

WATER-SOLUBLE AND FAT- SOLUBLE VITAMINS. VITAMINS AS COFACTORS

1.E

2.E

3.C

4.A

5.B

6.E

7.E

8.E

9.E

10.A

PRACTICAL LESSON 6

VITAMINS AS COFACTORS. FOLIC ACID. ASCORBIC ACID

1.E

2.E

3.A

4.C

5.D

6.D

7.E

8.D

9.C

10.E

QUESTIONS FOR TEST CONTROL MODULE 2

PRACTICAL LESSON 1

GENERAL METABOLISM. INTERMEDIARY METABOLISM

Choose the correct answer:

1. Metabolism is …:

A. the sum of all the chemical transformations taking place in a cell or organism;

B. the precursor which is converted into the end products;

C. the degradative phase in which organic nutrient molecules are converted into smaller, simpler end products;

D. the phase in which small, simple precursors are built up into larger and more complex molecules;

E. the pathway characterized release energy.

2. Catabolism is…:

A. the sum of all the chemical transformations taking place in a cell or organism;

B. the precursor which is converted into the end products;

C. the degradative phase of metabolism in which organic nutrient molecules are converted into smaller, simpler end products;

D. the phase in which small, simple precursors are built up into larger and more complex molecules;

E. the pathway characterized input of energy.

3. Anabolism is…:

A. the sum of all the chemical transformations taking place in a cell or organism;

B. the precursor which is converted into the end products;

C. the degradative phase of metabolism in which organic nutrient molecules are converted into smaller, simpler end products;

D. the biosynthesis phase of metabolism in which small, simple precursors are built up into larger and more complex molecules;

E. the pathway characterized release energy.

4. Which one of the following statements concerning purposes of the metabolism in human body is incorrect? Metabolism is necessary to…

A. obtain chemical energy by capturing solar energy;

B. convert nutrient molecules into the cell’s own characteristic molecules, including precursors of macromolecules;

C. polymerize monomeric precursors into macromolecules: proteins, nucleic acids, lipids, and polysaccharides;

D. synthesize biomolecules required for specialized cellular functions, such as messengers, pigments, membrane lipids;

E. degrades biomolecules required for specialized cellular functions, such as messengers, pigments, membrane lipids;

5. Metabolite is…:

A. the sum of all the chemical transformations taking place in a cell or organism;

B. the precursor which is converted into a product through a series of metabolic intermediates;

C. the degradative phases of metabolism in which organic nutrient molecules are converted into smaller, simpler end products;

D. the biosynthesis phase of metabolism in which small, simple precursors are built up into larger and more complex molecules;

E. the pathway characterized release energy.

6. Metabolic pathway is…:

A. the series of enzyme- catalyzed reactions;

B. the precursor which is converted into the end products;

C. the degradative phases of metabolism in which organic nutrient molecules are converted into smaller, simpler end products;

D. the biosynthesis phase of metabolism in which small, simple precursors are built up into larger and more complex molecules;

E. the pathway characterized release energy.

7. What the cell macromolecules do you know? Choose the incorrect answer.

A. proteins;

B. polysaccharides;

C. amino acids;

D. lipids;

E. nucleic acids.

8. What the precursor molecules do you know? Choose the incorrect answer.

A. amino acids;

B. sugars;

C. fatty acids;

D. proteins;

E. nitrogenous bases.

9. What the energy depleted end products do you know? Choose the incorrect answer.

A. CO₂;

B. H₂O;

C. NH₃;

D. C₆H₁₂O₆;

E. CH₃COCH₃.

10. Choose the incorrect answer. The important Co-enzyme A derivatives are…:

A. Acetyl CoA;.

B. Succinyl CoA;

C. Hydroxymetylglutaryl CoA;

D. Lecithinyl CoA;

E. Acyl CoA and Malonyl CoA.