Question

1 a) Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate the peptide bonds                  (5 marks)

b) Nucleic acids are chains of five-membered-ring sugars linked by phosphate groups. Each sugar is bonded to a base in a β-glycosidic linkage. Draw representative structures of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) indicating the location of the phosphodiester linkage, the β-glycosidic linkage and the key distinguishing feature between DNA and RNA.                                                                                                                                                                    (5 marks)

Legible and detailed answers please

Answer 1

DNA

Function   replicates and stores genetic information. genetic information contained within an organism.

Structure  two strands, arranged in a double helix. These strands are made up of subunits called nucleotides. Each nucleotide contains a phosphate, a 5-carbon sugar molecule and a nitrogenous base.

Length DNA is a much longer polymer than RNA. A chromosome, for example, is a single, long DNA molecule

Base Pairs Adenine and Thymine pair (A-T) Cytosine and Guanine pair (C-G)  

Location   DNA is found in the nucleus, with a small amount of DNA also present in mitochondria.

Ultraviolet (UV) Sensitivity DNA is vulnerable to damage by ultraviolet light.

RNA

Function   RNA converts the genetic information contained within DNA to a format used to build proteins, and then moves it to ribosomal protein factories.

Structure  RNA only has one strand, but like DNA, is made up of nucleotides. RNA strands are shorter than DNA strands. RNA sometimes forms a secondary double helix structure, but only intermittently.

Length RNA molecules are variable in length, but much shorter than long DNA polymers. A large RNA molecule might only be a few thousand base pairs long.

Base Pairs Adenine and Uracil pair (A-U) Cytosine and Guanine pair (C-G)

Location   RNA forms in the nucleolus, and then moves to specialised regions of the cytoplasm depending on the type of RNA formed.

Ultraviolet (UV) Sensitivity RNA is more resistant to damage from UV light than DNA.

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