Exam q dna

• How does the structure of DNA relate to the function?

  • Sugar phosphate backbone - provides strength and protects bases
  • Large / long - can store lots of information
  • Coiled / Helix - compact
  • Base sequence - allows information to be stored / specific base sequence codes for proteins
  • Double stranded - replication can occur semi conservatively
  • Weak hydrogen bonds - strands can separate
  • Covalent phosphodiester bonds - provides strength and protection
• Describe and explain the structure of DNA and how this aids accurate replication

  • Double stranded - allowing semiconservative replication as two template strands available
  • base pairing - holds two polynucleotide strands together
  • Hydrogen bonds are weak - allowing the strand to separate
  • Complementary base pairing - allows a complimentary copy of the strand to be formed
  • Base sequence on a template strands exposed - which acts like a template that can be copied
• Explain what’s meant by 3’ and 5’ end of dna

  • 5’ end has a phosphate group attached
  • 3’ end has an OH group attached

  
• What side of the DNA is complementary to the active site of DNA polymerase

  3’ of existing strand
• Human and grasshoppers have very similar percentages of each basis in the DNA. Use your knowledge of DNA structure and function to explain how this is possible.


  • Have different genes
  • Bases are in different sequences
  • Different polypeptide are coded for
• Use your knowledge of enzymes action to explain why the arrows in DNA application point in opposite directions

  • DNA has antiparallel strands
  • nucleotide is arranged differently
  • Enzymes have an active site with a specific shape
  • Only substrate with complementary end so 3’ end can bind with the active site of DNA polymerase
• DNA helicases important in DNA replication. Explain why

  • Breaks the hydrogen bonds between complementary base pairs
  • So two polynucleotide strands separate
  • Free nucleotide can attach to strand so it can act as a template
• Describe how ATP is resynthesised in cells

  • ADP and Phosphate are joined by a chemical bond
  • Through a condensation reaction with the help of ATP synthase
  • During respiration
• Describe how ATP is resynthesised In cells

  • ADP and Phosphate react to form ATP
  • In a condensation reaction catalysed by ATP synthase
  • During respiration
• Give two ways in which hydrolysis of ATP is used in cells 


  • To release energy for chemical reaction
  • Add phosphate to other substances and make them more stable
• Describe how mRNA is produced in the nucleus

  1. Helicase enzyme
  2. Breaks hydrogen bonds between complementary base pairs
  3. Separates two strands one of these strands acts as a template
  4. RNA nucleotides are attracted to exposed bases
  5. Attraction is according to base pair ruling
  6. RNA polymerase joins RNA nucleotides together by forming phosphodiester bonds
  7. Pre mRNA spliced to remove introns
• Describe how ATP molecule are formed from its components

  • Three phosphates , ribose , adenine
  • Condensation reaction
  • ATP synthase
• give two ways ATP is a suitable energy source

  • Releases relatively small amounts of energy which makes it efficient
  • Releases energy instantaneously
  • Phosphorylates other compounds making them more reactive
  • Can be rapidly resynthesised
  • Doesn’t leave the cell
• Two features of DNA and explain how each one’s important in semi conservative replication

  • Weak hydrogen bonds between complementary bases allows two strands to separate
  • Two strands and both can act as a template
  • Complementary base pairing allows accurate replication