Biological molecules 2

Which 2 bases are Purines ?

Adenine and Guanine

Which 2 bases are Pyrimidines ?

Thymine and Cytosine

How are 2 nucleotides joined together ?

By a condensation reaction between the deoxyribose sugar of one nucleotide and the phosphate group of another

How do nucleotides polymerise ?

By forming phosphodiester bonds between carbon-3 of the sugar and an oxygen atom of the phosphate

Why is DNA very stable ?

The sugar phosphate backbone / double stranded helix provides strength and protects hydrogen bonds

How does DNA being made of 2 strands which can be separated, make it adapted for its function ?

The 2 strands are held together by weak hydrogen bonds so they can separate easily during replication which makes copying DNA easier and more accurate

How does DNA being an extremely large molecule help to carry out its function ?

So organisms can carry and store all instructions needed for developing and functioning

Why is DNA helical and compact ?

Lets DNA coil tightly making it compact so large amounts can fit into the small nucleus

Why does DNA have a sugar phosphate backbone where base pairs are kept within the helical cylinder ?

The backbone protects the nitrogenous bases by keeping them inside the helix, reducing the chances of mutations so the sequence can be reliably passed on

How many hydrogen bonds do Adenine and Thymine have ?

2 hydrogen bonds

How many hydrogen bonds do Cytosine and Guanine have ?

3 hydrogen bonds

What is the role of mRNA

It carries instructions for assembling amino acids into proteins

What is the role of rRNA ?

Forms part of the structure of ribosomes and ‘glues’ them together