186. Explain the mechanism of phospholipids breakdown, shown at the scheme below:

Answer: Phospholipids are degraded by pancreatic phospholipase A₂, which hydrolytically excises the fatty acid residue at C(2) to yield the corresponding lysophosopholipids, which are also powerful detergents. Indeed, the phospholipid lecithin (phosphatidylcholine) is secreted in the bile, presumably to aid in lipid digestion. Pancreatic phospholipase A2, as does pancreatic lipase, preferentially catalyzes reactions at interfaces. Phospholipase C gives a diacylglycerol, phospholipase D gives a phosphatidate

187. Fill in the blanks:

Answer:

Section VI Structure and metabolism of amino acids

1. What is the number of amino acids involved in protein biosynthesis?

1. Twenty

2. Twelve

3. Twenty five

4. Fifteen

5. Thirty seven

2. Chose from listed below amino acids aliphatic one:

1. Isoleucine

2. Lysine

3. Histidine

4. Proline

5. Phenylalanine

3. Chose from listed below amino acids two aromatic ones:

1. Tyrosine

2. Phenylalanine

3. Serine

4. Cysteine

5. Alanine

4. Select from listed below amino acids non proteinogenous one:

1. β-Alanine

2. Aminoacetic acid

3. Histidine

4. Leucine

5. Proline

5. Note from listed below amino acids an acidic one:

1. Glutamate

2. Valine

3. Asparagine

4. Alanine

5. Lysine

6. In protein biosynthesis are involved:

1. L- amino acids only

2. D-amino acids only

3. D-amino acids predominantly

4. L-amino acids predominantly

5. Both D- and L- amino acids equally well

7. A polypeptide is shown to have a high pI value (approx. at pH 8,9). What from listed below amino acids is responsible for this property?

1. Arginine

2. Valine

3. Serine

4. Tyrosine

5. Cysteine

8. Denaturation of proteins is caused by:

1. Alteration of polypeptide chain folding (conformation)

2. Hydrolytic cleavage of peptide bonds

3. Reduction and cleavage of disulphide bonds.

4. Formation of new peptide bonds

5. Dissotiation of carboxyl groups

9. Sequence of amino acids in polypeptide chain is defined as the next structural level:

1. Primary

2. Secondary

3. Tertiary

4. Quaternary

5. Multimolecular complex

10. Note the correct value of normal protein concentration in human blood plasma:

1. 65-85 g/l

2. 25-40 g/l

3. 45-60 g/l

4. 85-100 g/l

5. 100-150 g/l

11. Proteins of blood plasma are divided into albumin and globulins. What is normal proportion of albumin to globulins (albumin/globulin coefficient)?

1. 2:1

2. 1:1

3. 5:1

4. 1:2

5. 1:5

12. Fibrinogen is an important protein of blood plasma. To what class of proteins belongs fibrinogen:

1. Glycoprotein

2. Albumin

3. Lipoprotein

4. Chromoprotein

5. Nucleoprotein

13. In proteins amino acids are linked covalently by:

1. Peptide bonds

2. Hydrogen bonds

3. Disulphide bonds

4. Hydrophobic interactions

5. Salt like bridges

14. Protein is a biopolymer which can be defined as:

1. Linear chain of L-amino acids

2. Branched chain of mononucleotides

3. Linear chain of amino sugars

4. Linear chain of nucleosides

5. Branched chain of D-amino acids

15. Domains are specific elements of the next structural level of protein molecule:

1. Tertiary

2. Secondary

3. Primary

4. Quaternary

5. Multimolecular complex

16. Secondary structure of proteins includes the next structural element:

1. β-Pleated sheets

2. Triple superhelix

3. Coplanarity of peptide bond

4. Disulphide bridges

5. Attachment of oligosaccharides to a polypeptide chain

17. The net charge of protein molecule depends from the next factors:

1. Amino acid composition

2. pH value of solution

3. Conformation of protein molecule

4. Quaternary structure of protein

5. Hydrophobic interactions between amino acid residues

18. Proteins can be precipitated by different agents. The precipitation with ammonium sulphate is convenient due to:

1. Fractional precipitation of protein mixtures and purification of selected proteins

2. Denaturation of precipitated protein at room temperature

3. Fragmentation of polypeptide chain to oligopeptides

4. Irreversible precipitation of protein from investigated material

5. Precipitation of amino acids accompanying proteins

19. The concentration of protein in blood serum of a patient was on level of 40 g/l. Such situation can be classified as follows:

1. Hypoproteinemia

2. Dysproteinemia

3. Hyperproteinemia

4. Normal state

5. Paraproteinemia

20. Disulphide bridge in protein molecules is formed between the next amino acids:

1. Cysteine-cysteine

2. Lysine-aspartic acid

3. Tyrosine - histidine

4. Proline-tryptophan

5. Histidine-arginine

22. Salt like bridges (ionic bonds) in protein molecule are formed between the next amino acids:

1. Lysine-glutamic acid

2. Leucine-alanine

3. Phenylalanine-tyrosine

4. Aspartic acid-methionine

5. Serine-cysteine

23. Glutathion is a tripeptide possessing reducing properties. What amino acid residue is responsible for reductive properties of glutathion?

1. Cysteine

2. Glutamic acid

3. Glycine

4. Valine

5. Aspartic acid

24. An amino acid that does not form an α-helix is:

1. Proline

2. Valine

3. Tyrosine

4. Tryptophan

5. Alanine

25. Which of the following is a dipeptide?

1. Anserine

2. Glutathione

3. Insulin

4. Glucagon

5. β -Lipoprotein

26. Which of the following is a tripeptide?

1. Glutathione

2. Anserine

3. Oxytocin

4. Glucagon

5. Kallidin

27. Each turn of α-helix contains the amino acid residues (number):

1. 3.6

2. 3.0

3. 4.2

4. 4.5

5. 5.6

28. At the lowest energy level α-helix of polypeptide chain is stabilised:

A. By hydrogen bonds formed between the H of peptide N and the carbonyl O of the residue

B. Disulphide bonds

C. Non polar bonds

D. Ester bonds

29. In proteins the α-helix and β-pleated sheet are examples of:

A. Secondary structure

B. Primary structure

C. Tertiary structure

D. Quaternary structure

30. The a-helix of proteins is:

1. Stabilised by hydrogen bonds between NH and CO groups of the main chain

2. A pleated structure

3. Made periodic by disulphide bridges

4. A non-periodic structure

31. A disulphide bond can be formed between:

1. Two cysteine residues

2. Two methionine residues

3. A methionine and a cysteine residue

4. Two serine residues

5. Two valine residues

32. In a child, consuming meal of plant origin for a long time growth retardation, anemia, liver and kidney impairment were observed. The cause of such state is deficiency in diet of the next nutrients:

1. Essential amino acids

2. Lipids

3. Carbohydrates

4. Mineral macroelements

5. Carotene

33. Pyruvic acid can be obtained by transamination of alanine with:

A. α- ketoglutaric acid

B. Acetoacetic acid

C. α- OH butyric acid

D. Phosphoenol Pyruvic acid

E. Fumaric acid

34. The product of glutamate decarboxylation is:

1. Gamma-amino butyrate

2. Putrescine

3. Taurine

4. Oxaloacetate

5. α-Ketoglutarate

35. A vasodilating compound is produced by the decarboxylation of the amino acid:

A. Histidine

B. Aspartic acid

C. Glutamine

D. Arginine

E. Glutamic acid

36. One of the products of amino acid deamination by amino acid oxidase is:

1. Hydrogen peroxide

2. Water

3. Carbone dioxide

4. Nitric oxide

5. Protons

37. An important reaction for the synthesis of amino acid from carbohydrate intermediates is transamination which requires the cofactor:

A. Pyridoxal phosphate

B. Riboflavin

C. Niacin

D. Thiamin

E. Folic acid

38. Which of the following enzymes catalyses reactions in the biosynthesis of both catecholamines and indoleamines (serotonin)?

1. Aromatic amino acid decarboxylase

2. Dopamine β-hydroxylase

3. Phenylethanolamine N-methyltransferase

4. Tryptophan hydroxylase

5. Tyrosine hydroxylase

39. The main sites for oxidative deamination are:

A. Liver and kidney

B. Skin and pancreas

C. Intestine and mammary gland

D. Lung and spleen

E. Brain

40. The amino acids involved in the synthesis of creatin are:

A. Arginine, glycine, active methionine

B. Arginine, alanine, glycine

C. Glycine, lysine, methionine

D. Arginine, lysine, methionine

E. Glycine, lysine, alanine

41. Note amino acids, which are participants of creatine biosynthesis:

1. Arginine.

2. Lysine.

3. Methionine.

4. Tryptophan.

5. Phenylalanine.

42. The amino acid that undergoes oxidative deamination at significant rate is:

A. Glutamate

B. Aspartate

C. Alanine

D. Glutamine

E. Serine

43. Allosteric inhibitor of glutamate dehydrogenase is:

A. ATP

B. ADP

C. AMP

D. GMP

E. NAD⁺

44. In recognition of hepatitis the determination the following enzymes activity in blood has diagnostic significance:

A. Amino transferases