2.3 nucleotides and proteinsynthesis

• phophate group • pentose sugar • nitrogenous base

• deoxyribose sugar • phopshate group • nitrogensou base • Adenine • Cytosine • Guanine • Thymine

• ribose sugar • phopshate group • nitrogensou base • Adenine • Cytosine • Guanine • Uracil

• double ringed structure • Adenine and guanine - 2n’s so double ringed

• single ring structure • thymine • uracil • cytosine

• double helix • base pairs are joined by hydrogen bonds - A&T have 2, C&G have 3 • alternatign deoxyribose sugar and phosphate groups bonded otgetehr to form sugar-phopsphate backpbone by phosphodiester bonds • 2 parallel strands are arranged so run opposite directions - antiparallel • 5’ -> 3’ direction - carbon 5 linked to phoopshatye group which bonds to carbon 3 of anotehr deoxyribose sugar • deoxyribose has H on the bottom of the second carbon

• ribose sugar - has OH below the secpnd carbon • adenine and uracil have 2 bonds • cytosine and and Guanine have 3 bonds

• nucelotides joined via condesnation reaction • occur between phophate group of one nucleotide and the pentose suagr of next nucleotide • condensation reaction forms a phosphodiester bond

• 3 phosphates (ADP-2, AMP-1) • ribose sugar • adenosine

• emergy required for anabolic reactions and mving substances within cells • also required for muscle contraction and conduction of nerve impulses • ATP form respiration used to transfer energy in all energy-requiring processes inc ells

3

2

• Both strands are used as templates and complementary base pairing occurs between the template strands and free nucleotides • each new DNA molecule consists of one strand that is conserved from the DNA molecule being copied and one strand that is newly created by the cell

enzyme DNA helicase unwinds the DNA double helix by breaking the hydrogen bonds between the base pairs on the two antiparallel strands Free DNA nucleotides are attracted to the exposed bases on each of the template strands The free nucleotides contain extra phosphates, and are known as activated nucleotides Adjacent nucleotides are then joined together by the enzyme DNA polymerase to form a new sugar-phosphate backbone DNA polymerase catalyses condensation reactions between the deoxyribose sugar and phosphate groups of adjacent nucleotides The resulting bond is a phosphodiester bond Hydrogen bonds form between complementary bases to form the ladder of the DNA double helix

Retaining one original DNA strand maximises accuracy during the DNA replication process, as each new DNA strand is created from an existing template Each new cell will always contain the same genetic information as its parent, meaning that genetic continuity is ensured between generations of cells This is important because cells in our body are replaced regularly and we need the new cells to carry out the same roles as the parent cells

random spontaneous mutations deletion insertion point insertion substitution