Nucleic Acid

• What is the use of hydrogen ions?

  They can determine the pH of a solution
• What is the use of iron ions?

  They're a component of haemoglobin

  Iron ions combine with oxygen and CO2 whilst also acting as a buffer to maintain pH
• What is the use of sodium ions?

  They're involved in the cotransport of glucose and amino acids:

  • Their electrochemical gradient provides the energy required for glucose uptake
  • The same electrochemical gradient is used to move amino acids into cells
• What is the use of phosphate ions?

  They're components of DNA, ATP and phospholipids:

  • In DNA they provide a negative charge to the backbone and the overall charge of DNA
  • In ATP the high energy phosphate ions store chemical energy that can be released when needed
  • In phospholipids they make the head hydrophilic
• In DNA polynucleotides:

  • Complementary base pairing allows for accurate code replication
  • Strong phosphodiester bonds hold together the sugar phosphate backbone
  • Deoxyribose sugar is present
  • The base sequence allows for information to be stored
  • Many hydrogen bonds are between bases
• Give two features of DNA and explain how they are important in semi-conservative replication of DNA

  • Their double stranded helical structure provides a protective and stable structure
  • Their complementary base pairing ensures the accuracy of DNA replication
• What properties make ATP a suitable source of energy?

  • It only requires a single reaction
  • The energy is released in small manageable amounts
  • It's soluble meaning that it's rapidly available for biochemical processes
• Why do we synthesise such a large amount of ATP day to day?

  ATP only releases small amounts of energy so lots of it needs to be synthesised
• Why is ATP useful in so many biological processes?

  • It releases energy in manageable amounts and can be broken down in a single reaction making energy available rapidly
  • The addition of a phosphate lowers the activation energy required then ATP is reformed
• Describe the structure of DNA

  It's a polymer of nucleotides;

  • Each nucleotide is formed from deoxyribose, a phosphate group and a nitrogenous base;
  • There are phosphodiester bonds between nucleotides;
  • Double helix strands are held by hydrogen bonds;
  • Nitrogenous bases are adenine, thymine, cytosine and guanine.
• RNA polynucleotides:

  • Complementary base pairing is present
  • They're short as they're a copy of one gene
  • Ribose is the sugar
  • Phosphodiester bonds are in the sugar phosphate backbone
  • It's single stranded structure allows for translation
• DNA nucleotide:

  • Numerous hydrogen bonds between the two strands ensures stability of the molecule
  • Hydrogen bonds are easily broken so that the two strands can separate during DNA replication
  • Due to it having two strands each can act as a template
• Structures in nucleotides and their functions:

  • Nucleotides are large molecules so lots of genetic information can be stored.
  • Their base sequence codes for a sequence of amino acids in a protein.
  • Their coiled helical structure makes it compact so it can be stored in small places.
  • The sugarphosphate backbone provides strength and protects bases from corruption.
• What are the similarities and differences between nucleotides (DNA & RNA)?

  • They both have phosphate groups and these bases; adenine, cytosine and guanine
  • DNA has deoxyribose and RNA has ribose
  • DNA has thymine and RNA has uracil