Nucleic Acids and Nucleotide Structure

Practice flashcards covering the chemical building blocks, bonds, and structures of nucleotides, ATP, DNA, and RNA.

Nucleotide

A residue and building block of nucleic acids (DNA or RNA) assembled from three components: phosphoric acid, a monosaccharide, and an organic base.

Phosphoric acid ($H_3PO_4$)

A nucleotide building block that is present as $H_3PO_4$ at low pH, as dihydrogen phosphate or hydrogen phosphate anions at physiological pH (around $7$), and as $PO_4^{3-}$ at high alkaline pH.

D-ribose

An aldopentose monosaccharide found in RNA that adopts a five-membered furanose ring with an alcohol functional group at carbon-2 and an anomeric hydroxyl group at the top (beta configuration).

Deoxyribose

A pentose monosaccharide found in DNA that adopts a cyclic furanose ring and is characterized by the absence of an oxygen atom at carbon-2.

Heterocyclic amines

Amine functional groups incorporated into cyclic rings containing nitrogen and carbon atoms, serving as the organic bases of nucleotides.

Purines

Heterocyclic amine bases composed of two fused rings (a six-membered ring and a five-membered ring), comprising adenine and guanine.

Pyrimidines

Heterocyclic amine bases essentially made up of a single ring, comprising cytosine, thymine, and uracil.

Adenine

A purine organic base found in both DNA and RNA nucleotides.

Guanine

A purine organic base found in both DNA and RNA nucleotides.

Cytosine

A pyrimidine organic base found in both DNA and RNA nucleotides.

Thymine

A pyrimidine base found only in DNA and not found in RNA.

Uracil

A pyrimidine base found only in RNA and not found in DNA.

N-glycosidic bond

The beta-oriented covalent bond that connects a nitrogen atom in an organic base to the anomeric carbon (carbon-1) of the monosaccharide.

Phosphoester bond

The covalent bond that connects a phosphate unit to the fifth carbon atom of the monosaccharide ring.

Phosphoanhydride bond

An energy-rich covalent bond linking phosphate units together in ATP or ADP, the exothermic hydrolysis of which releases energy and a phosphate ion.

Adenosine triphosphate (ATP)

A nucleotide derivative composed of the base adenine, the sugar ribose, and three phosphate groups linked via phosphoester and phosphoanhydride bonds.

Adenosine diphosphate (ADP)

The product formed when ATP undergoes hydrolysis, consisting of adenine, ribose, and two phosphate groups joined by a phosphoanhydride bond.

Adenosine monophosphate (AMP)

A nucleotide containing adenine, ribose, and a single phosphate group, which can form a cyclic structure known as cyclic AMP.

$3', 5'$ Phosphodiester bond

A covalent linkage connecting the $3'$ carbon of one monosaccharide to the $5'$ carbon of the next monosaccharide via a phosphate group, forming the polynucleotide backbone.

$5'$ terminus ($5'$ end)

The end of a polynucleotide chain where the fifth carbon position of the monosaccharide is not connected to another nucleotide.

$3'$ terminus ($3'$ end)

The end of a polynucleotide chain where the hydroxyl group on the third carbon position of the monosaccharide is not linked to another nucleotide.