Nucleotides and DNA

What is a nucleotide?

The building block from which nucleic acids form

What are the three types of nucleic acid?

Deoxyribonucleotide, ribonucleotide, ATP (adenosine triphosphate)

What are the similarities between the nucleotides?

All have a 5 carbon sugar, a phosphate group and an organic base (which is adenine)

What are the differences between the nucleotides?

In DNA, the 5 carbon sugar is deoxyribose but in RNA and ATP this is ribose. DNA and RNA only have one phosphate group while ATP has three

What is the structure of ATP?

The energy currency of the cell, with high energy phosphanhydride bonds (the final end bond has the highest energy of 30.6kJ/mol) as part of the triphosphate, adenine as its organic base and a Penrose sugar

What are the stages in ATP?

The final bond in ATP is broken to release energy, and the molecule becomes ADP (adenosine diphosphate), then AMP (adenosine monophosphate) as the next bond breaks to release energy, then adenosine ad the final phosphate is lost so all that is left is the sugar and the base

How is ATP synthesised?

It is phosphorylated from ADP and Pi (an inorganic phosphate) - an endergonic reaction requiring energy

What is dephosphorylation?

The removal of a phosphate group to release energy in the exergonic reaction

Where is ATP used?

Active transport, muscle contraction, nerve transmission, protein synthesis

Why is ATP important?

The uncontrolled release of energy from glucose would result in an increase in temperature that would destroy cells. Instead, living organisms use the gradual release of energy in small steps to produce ATP. ATP can be hydrolysed to release energy as required. It is a means of transferring free energy from energy rich compounds (glucose) to cellular reactions where energy is needed.

What are the forms of phosphorylation?

Oxidative phosphorylation and photosphosphorylation

What is oxidative phosphorylation?

Occurs on the membranes of the mitochondria during aerobic respiration

What is photophosphorylation?

This occurs on the membranes of the chloroplasts during photosynthesis

What are the advantages of ATP?

Only one enzyme is needed to release energy from ATP while many are needed to release energy from glucose

ATP releases energy in small amounts where and when needed, while glucose contains large amounts of energy which may not be needed immediately

ATP provides a common source of energy for many different chemical reactions, increasing efficiency and control by the cell

ATP is known as the universal energy currency in living organisms

What is DNA?

Deoxyribonucleic acid is a polymer made up of two subunits (monomers) called nucleotides

What are the organic bases of DNA?

Pyrimidines: have single ring structures - cytosine, thymine, uracil (RNA only)

Purines: have double ring structures - adenine, guanine

How is a molecule of DNA formed?

From millions of nucleotides joined together in a long chain by condensation reactions

What is a phosphodiester bond?

A bond formed between the phosphate group on C5 of one sugar and the hydroxyl (OH) group on C3 of the next. This also produces a molecule of H2O

What is the structure of a DNA helix?

A double stranded molecule is formed in a helix pattern as the strands are antiparallel. The sugar phosphates are on the outside, the two strands are held together by hydrogen bonds between the bases, so two antiparallel strands form one molecule of DNA

Which bases are paired?

A=T (adenine and thymine form two weak hydrogen bonds); C=-G (cytosine and guanine form three weak hydrogen bonds)