000475

heat to a boil. Add 5 drops of a 10% solution of Pb (CH

COO)

to the resulting

alkaline solutionand again boil. What are you watching? Specify the color of the

obtained precipitate. What α-amino acids can be discovered by this reaction?

Write a reaction scheme.

Experiment 4. Precipitation of proteins with tannin

. Mix a few drops of the

tannin solution with a few drops of the protein solutionin a test tub

e.W

hat are

you observing? How can this phenomenon be explained?

LESSON 25.

CHEMISTRY OF NUCLEIC ACIDS

Required basic level of knowledge.

Structure and properties of ribose and deoxyribose. Definition, scheme of

formation of glycosides and glycosidic bonds. The scheme for the formation of

complex ester bonds in the phosphorus derivatives of ribose and deoxyribose. The

mechanism of hydrogen bond formation. Complementarity of nitrogenous bases.

Questions for the preparation for the lesson.

1. Nitrogen bases. Definition. The structure of purine and pyrimidine with

atomic numbering, the structure and lactim-lactam transformations of purine

(guanine) and pyrimidine (uracil, cytosine, thymine) nitrogen bases.

2. Nucleosides. Definition, the scheme for the formation of nucleosides

and N‑glycosidic bonds. Nomenclature of purine and pyrimidine nucleosides.

Numbering of atoms in a nitrogenous base and in pentose.

3. Nucleotides. Definition, scheme for the formation of 5’-nucleotides and

3’-nucleotides, complex ester bond. Nomenclature of nucleotides. Structure

of ATP, biological role. Cyclic nucleotides: 3’, 5’-cAMP, 2’, 3’-cAMP, 3’, 5’-

cGMP, 2’, 3’-cGMP. Biological role.

4. Nucleic acids. Definition, variety. Distinctions of DNA from RNA. Types

of RNA, distinctive features. Scheme and conditions for the hydrolysis of

nucleic acids.

5. Nucleic Acid Structures:

• primary structure of nucleic acids – composition and sequence of

nucleotides. Structure of the polynucleotide chain. Scheme of formation of 3’,

5’-phosphodiester bond on the example of a dinucleotide.

• secondary structure of DNA and t‑RNA. The role of hydrogen bonds in

complementary pairs of nitrogenous bases in the formation of the secondary

structure of nucleic acids.