DNA & Protein Synthesis Assessment Flashcards
2.5 What is the basic structure of a mononucleotide?
Deoxyribose or ribose linked to a phosphate and a base (adenine, thymine, uracil, cytosine or guanine).
DNA nucleotide:
A deoxyribose sugar with hydrogen at the 2’ position.
A phosphate group.
One of four nitrogenous bases (adenine, thymine, cytosine or guanine).
RNA nucleotide:
A ribose sugar with a hydroxyl (OH) group at the 2’ position.
A phosphate group.
One of four nitrogenous bases (adenine, uracil, cytosine or guanine).
The presence of the 2’ hydroxyl group makes RNA more susceptible to hydrolysis. This is why DNA is the storage molecule and RNA is the transport molecule with a shorter molecular lifespan.
2.5 What are purine and pyrimidine bases?
The nitrogenous base molecules that are found in the nucleotides of DNA (A, T, C, G) and RNA (A, U, C, G) occur in two structural forms: purines and pyrimidines.
The bases adenine and guanine are purines - they have a double ring structure.
The bases cytosine, thymine and uracil are pyrimidines - they have a single ring structure.
2.5 What are the phosphodiester bonds?
DNA and RNA are polymers, meaning that they are made up of many nucleotides joined together in long chains.
Separate nucleotides are joined via condensation reactions. These condensation reactions occur between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide.
A condensation reaction between two nucleotides forms a phosphodiester bond. It is called a phosphodiester bond because it consists of a phosphate group and two ester bonds (phosphate with double bond oxygen attached - oxygen - carbon).
The chain of alternating phosphate groups and pentose sugars produced as a result of many phosphodiester bonds is known as the sugar-phosphate backbone.
