Nucleic Acids Flashcards
What are the two nucleic acids?
DNA - Deoxyribonucleic acid
RNA - Ribonucleic acid
What are the three components of a nucleotide?
- Pentose sugar (5 C atoms)
- a phosphate group
- a nitrogen containing organic base (C, T, A, U, G)
How are the three components of a nucleotide joined?
Condensation reactions, to form a single nucleotide known as a mononucleotide.
How do mononucleotides bond?
The deoxyribose sugar and phosphate group of two different monomers join in a condensation reaction to form a phosphodiester bond. This structure is known as a dinucleotide.
How are polynucleotides formed?
Dinucleotides are bonded continuously by phosphodiester bonds creating a long polynucleotide chain.
What is RNA?
RNA is a single, relatively short, polynucleotide chain in which the pentose sugar is always ribose and the organic bases are A, G, C, and U.
What is the structure of DNA?
Made up of two nucleotide strands, which are extremely long and are joined by hydrogen bonds formed between certain bases. The nucleotide strands run antiparallel.
Which bases pair with which?
Adenine always pairs with thymine and guanine always pairs with cytosine. These are known as complementary base pairs. The ratio of each of the pairs varies from species to species.
What is the structure of the double helix of DNA?
The nucleotide chains are twisted like a ladder. The uprights of phosphate and deoxyribose wind round one another to form a double helix, forming the structural backbone of DNA.
How does the phosphodiester backbone contribute to the stability of DNA?
The backbone protects the more chemically reactive organic bases inside the double helix.
How do the hydrogen bonds between the nucleotide chains contribute to the stability of DNA?
They form bridges between the antiparallel chains. The higher proportion of C-G bonds there are, the more stable as they are bonded by 3 hydrogen bonds, whereas A-T are bonded by 2.
What is the key function of DNA?
The hereditary material responsible for passing and storing genetic material from cell to cell.
Why does DNA only rarely mutate?
Because it is a stable structure which normally passes through generations without change.
What do the hydrogen bonds allow the DNA molecules to do?
The two separate strands are able to separate during DNA replication and protein synthesis.
Why is it significant that DNA is a large molecule?
It is able to carry an immense amount of genetic information.
