Nucleotide and Nucleoside Structures Quiz

Nucleic Acids

• Nucleic acids are composed of pentose sugar, nitrogenous base, and phosphate molecules.
• There are two types of nucleic acids: DNA (deoxynucleoside phosphate) and RNA (nucleoside phosphate).

Nucleoside

• A nucleoside is a combination of a nitrogenous base and a sugar molecule.
• The sugar molecule is usually ribose or deoxyribose.
• The base is linked to the sugar molecule at carbon 1, and the phosphate group is linked to the sugar molecule at carbon 5.

Pentose Sugars

• Pentose sugars are 5-carbon monosaccharide molecules.
• There are two types of pentose sugars: ribose and deoxyribose.
• Ribose is the pentose sugar found in RNA.
• Deoxyribose is the pentose sugar found in DNA, and it lacks one oxygen atom at carbon 2.

Nitrogenous Bases

• Nitrogenous bases are heterocyclic amines that can accept a proton.
• There are two types of nitrogenous bases: purine and pyrimidine.
• Purine bases have a double-ringed structure and include adenine and guanine.
• Pyrimidine bases have a 6-membered ring structure and include cytosine, thymine, and uracil.
• Adenine and guanine are found in both DNA and RNA, while thymine is only found in DNA and uracil is only found in RNA.

Phosphodiester Bond

• A phosphodiester bond is a chemical bond formed between the hydroxyl group of one nucleotide and another nucleotide.
• It is the bond between two nucleotides, with the 5' end of one nucleotide and the 3' end of another.

Nomenclature

• Nucleotides are named based on the nitrogenous base and the sugar molecule.
• Examples of nucleotide names include deoxyadenosine monophosphate (dAMP), deoxyguanosine monophosphate (dGMP), and deoxythymidine monophosphate (dTMP).

DNA Structure

• The DNA double helix structure was discovered by James Watson and Francis Crick in 1953.
• The structure consists of two helical polynucleotide chains coiled around a common axis.
• The chains run in anti-parallel directions, and the phosphate and deoxyribose units are outside the helix.
• The purine and pyrimidine bases are inside the helix, and the planes of the bases are perpendicular to the helix axis.
• The diameter of the helix is 20A, and the adjacent bases are separated by 34A along the helix.
• The helical structure repeats after 10 residues on each chain at intervals of 34A.
• The two chains are held together by hydrogen bonds between pairs of bases.
• Adenine pairs with thymine, and guanine pairs with cytosine.
• Any sequence of bases may occur along a polynucleotide chain, and the precise sequence of bases carries genetic information.

Chargaff's Rule

• Chargaff's Rule, also known as the Fidelity Rule, states that the concentration of adenine is equal to that of thymine, and the concentration of guanine is equal to that of cytosine.
• This rule was discovered by Erwin Chargaff in 1950 and provided important clues about the structure of DNA.