Nucleic Acids

Question 1

Nucleotides:

What is a nucleotide composed of?

Answer 1

• phosphate group
• five carbon (pentose) sugar
• nitrogenous base

remember, the sugar will be different depending on DNA or RNA

Question 2

Nucleotides:

Explain the structure of the ribose sugar and where each carbon is attached to?
* 1’
* 3’
* 5’

Answer 2

Each carbon is assigned a number in a clockwise direction, with the first carbon labelled 1’ (one prime) and the last carbon 5’.
* 1’ –> nitrogenous base
* 3’ –> phosphate of following nucleotide
* 5’ –> phosphate group of the nucleotide

Question 3

Nucleotides:

What are the bonds joining the nucelotides together?

Answer 3

Strong covalent bonds known as phosphodiester bonds
* formed via condensation reactions
* exist between sugar group of one nucleotide and the phosphate group of another

often referred to as the sugar-phosphate backbone of nucleic acids

Question 4

DNA:

What are four properties of DNA?

DNA = deoxyribosenucleic acid

Mention; the type of sugar, the base pairs, and the physical build

Answer 4

• a deoxyribose sugar
• adenine (A) will always pair with thymine (T) with two hydrogen bonds
• guanine (G) will always pair with cytosine (C) with three hydrogen bonds
• double-stranded, bonded via complementary base pairing, forming a double-helix which runs in an antiparallel fashion

Question 5

RNA:

What is RNA and what are four properties of it?

Answer 5

A single stranded molecule, variety of different forms and is found in many different parts of the cell; primarily involves in the synthesis of proteins

• a ribose sugar
• adenine (A) will always pair with uracil (U) with two hydrogen bonds instead of (T) thymine which is only in DNA
• single-stranded

Question 6

RNA:

What are the three types of RNA?

Mention the function of each type of RNA

Answer 6

• Messenger RNA: carries genetic information from the nucleus to the ribosomes for protein synthesis
• Transfer RNA: delivers specific amino acids to the ribosome after recognising specific nucleotide sequences on mRNA, each tRNA contains specific anticodons which are complementary to the codons on mRNA and specific to an amino acid
• Ribosomal RNA: serves as the main structural component of ribosomes within cells - contains ribose sugar; no thymine, uracil instead; temporary molecules

ALWAYS mention the anticodons in tRNA.