Question

What is the simplest evolutionary explanation for:

1. Nucleotide synthesis uses several amino acids
2. Deoxyribose is made from ribose

Hint: Determine which one came first. Provide detailed answer for full credit!

Answer 1

Proteins are made up of amino acids.Both DNA and RNA are made up of a series of nucleotides.A nucleotide is composed of a five-carbon sugar,a nitrogenous base and a phosphate group.

Nucleotide synthesis occurs in the cytosol of the liver where all the necessary enzymes are present as a macro- molecular aggregate.

There are two pathways for the synthesis of nucleotide.

1)Salvage pathway

2) De novo pathway

The salvage pathway uses free bases via a reaction with phosphoribosyl pyrophosphate (PRPP) and generation of nucleotides

De novo pathways synthesize pyrimidines and purine nucleotides from amino acids,carbon dioxide,folate derivatives and phosphoribosyl pyrophosphate (PRPP).

(b) deoxiribose is made from ribose

DNA contains the sugar deoxiribose while RNA contains ribose sugar.The difference between deoxiribose and ribose is that ribose has one more -OH group than deoxiribose,which has -H attached to the second carbon in the ring.

Deoxiribose is derived from ribose.Ribose form five- member ring composed of four carbon atoms and one oxigen atom.Hydroxyl(-OH)group are attached to three of the carbons.The fourth carbon in the ring is attached to the fifth carbon atom and hydroxyl group .Deoxyribose is formed by the replacement of the hydroxyl group at the 2 position with hydrogen,that leads to the net loss of oxygen atom.