BIOCHEMISTRY in Questions and Answers - Alimov A.M. - 2016

SECTION 9. METABOLISM OF NUCLEIC ACIDS

Question 1. WHAT IS A nucleic acid?

Answer: A nucleic acid is a polymer composed of mononucleotides.

Question 2. What are the Types of Nucleic acids?

Answer: Deoxyribonucleic acid, ribonucleic acid.

Question 3. What is a nucleoside?

Answer: A nucleoside is a compound consisting of a nitrogenous base and a pentose.

Question 4. What is a nucleotide?

Answer. A nucleotide is a compound consisting of a nitrogenous base, a pentose, and phosphoric acid

Question 5. Which nitrogenous bases are present in DNA?

Answer: Purine nitrogenous bases: adenine and guanine; pyrimidine bases: cytosine, thymine

Question 6. Which nitrogenous bases are present in RNA?

Answer: Purine nitrogenous bases: adenine and guanine; pyrimidine bases: cytosine, uracil

Question 7. What type of bond connects NUCLEOTIDES in a nucleic acid?

Answer: 3',5'-phosphodiester bond

Question 8. What carbohydrate is a component of DNA and RNA?

Answer: DNA contains deoxyribose, while RNA contains ribose.

Question 9. How are nucleosides formed?

Answer: Nucleosides are formed by the establishment of an N-glycosidic bond between the 9th nitrogen atom of Purines or the 1st nitrogen atom of Pyrimidines and the 1st carbon atom of a pentose (ribose or 2-deoxyribose).

Question 10. What are Chargaff's rules?

Answer: -the molar ratio of adenine to thymine is equal to 1; -the molar ratio of guanine to cytosine is equal to 1

-the sum of purine nucleotides is equal to the sum of pyrimidine nucleotides

-in DNA from different sources, the (G+C)/(A+T) ratio, known as the coefficient of Specificity, varies.

Question 11. What is the Introduction/11.html">Secondary Structure of DNA?

Answer: It is a right-handed helix consisting of two antiparallel polynucleotide chains

Question 12. How is the DNA helix structured?

Answer: There are 10 Base Pairs per turn. The DNA strands are complementary to each other

Question 13. What chemical bonds maintain the secondary structure of DNA?

Answer: 1. Hydrogen Bonds between complementary nitrogenous bases

2. Hydrophobic interactions

Question 14. How many Hydrogen bonds are formed between complementary pairs?

Answer: 2 hydrogen bonds form between the complementary adenine-thymine pairs, and 3 bonds between guanine-cytosine

Question 15. What are the structural differences between DNA and RNA? Answer:

Question 16. What are the MAIN TYPES OF RNA?

Answer: 1. Messenger RNA (mRNA)

2. Transfer RNA (tRNA)

3. Ribosomal RNA (rRNA)

Question 17. What is the secondary structure of tRNA?

Answer: The presence of a significant number of minor nucleotides gives the secondary structure of tRNA a "cloverleaf" shape

Question 18. What are the Functions of tRNA?

Answer: 1. Transport (delivers a specific amino acid to the ribosome at the site of Protein Synthesis)

2. Adapter (ensures the Translation of information from the nucleotide language to The amino acid language)

Question 19. What are Nucleoproteins?

Answer: These are complex Proteins whose prosthetic group is represented by Nucleic Acids

Question 20. What is deoxyribonucleoprotein (DNP)?

Answer: It is a nucleoprotein whose prosthetic group is represented by DNA (Chromatin)

Question 21. What is a ribonucleoprotein?

Answer: It is a nucleoprotein whose prosthetic group is represented by RNA (ribosome)

Question 22. What proteins are components of DNP?

Answer: 1. Histones

2. Acidic non-histone proteins

Question 23. What is the end product of purine nitrogenous base degradation?

Answer: Uric acid

Question 24. What are the End products of pyrimidine nitrogenous base degradation?

Answer: NН₃, СО₂, β-Alanine (from uracil and cytosine), and β-aminoisobutyrate (from thymine)

Question 25. What is the common intermediate product in AMP and GMP synthesis?

Answer: Inosine monophosphate

Question 26. How is the Synthesis of purine nucleotides regulated?

Answer. AMP and GMP inhibit the synthesis of PRPP and phosphoribosylamine

Question 27. What substances are involved in pyrimidine synthesis?

Answer: Glutamine, aspartate, СО₂

Question 28. What is the common intermediate metabolite in the synthesis of all pyrimidine nucleotides?

Answer: UMP (uridine monophosphate)

Question 29. Which protein is involved in the Formation of Deoxyribonucleotides?

Answer: Thioredoxin

Question 30. What types of template-directed syntheses exist?

Answer: 1. Replication

2. METABOLISM/31.html">Transcription

3. Translation

Question 31. What is replication?

Answer: The synthesis of daughter DNA strands on a DNA template

Question 32. What is repair?

Answer: The restoration of DNA Structure upon damage

Question 33. What is transcription?

Answer: The copying of Genetic information from DNA to messenger RNA (mRNA)

Question 34. What is translation?

Answer. The synthesis of polypeptide chains in the ribosome using an mRNA template

Question 35. What processes occur during replication?

Answer: 1. Unwinding of the parental DNA strands

2. Formation of replication forks

3. Synthesis of An RNA primer

4. Synthesis of DNA strands by DNA polymerase III in the 5' —> 3' direction

5. Removal of RNA primers

6. Joining of Okazaki fragments

Question 36. What is pre-mRNA Processing?

Answer. It is the post-transcriptional maturation of pre-mRNA, including the following stages: Modification of the 5' and 3' ends (5'-capping, 3'-polyadenylation); excision of introns; and joining of exons (splicing)

Question 37. What are The properties of The Genetic Code?

Answer: 1. Triplet nature

2. Non-overlapping

3. Degeneracy

4. Specificity

5. Universality

6. Colinearity

7. Polarity

Question 38. What is a codon?

Answer: A codon is a triplet of nucleotides that encodes a single amino acid

Question 39. What are the stages of translation?

Answer. 1. Initiation

2. Elongation

3. Termination

Question 40. Which codon serves as the initiation codon?

Answer: AUG

Question 41. Which codons are termination codons?

Answer: UAA, UAG, UGA

Question 42. Which functional sites are formed in the ribosome during protein synthesis?

Answer: Peptidyl and aminoacyl sites

Question 43. Which protein factors are involved in protein synthesis?

Answer: Initiation, elongation, and termination protein factors

Question 44. What post-translational modifications occur after the polypeptide chain is assembled on the ribosome?

Answer: 1. Removal of The initiating amino acid from the N-terminus

2. Limited proteolysis

3. Formation of Disulfide Bonds

4. Addition of a prosthetic group

5. Modification of amino acid side chains

6. Folding (Formation of the three-dimensional conformation)

Question 45. Which enzyme catalyzes DNA Synthesis using an RNA template?

Answer. RNA-dependent DNA polymerase (Reverse Transcriptase, recombinase/revertase)

Question 46. What are mitogens?

Answer: Factors that specifically stimulate DNA replication. These are primarily epithelial growth factors, platelet-derived growth factors, etc.

Question 47. What are morphogens?

Answer: Substances that direct and guide Cell Differentiation

Question 48. How do Antibiotics affect protein synthesis?

Answer. They act as inhibitors at various stages of template-directed synthesis