1.5 Nucleic Acids

• 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 hydrophillic.
• Fill in the following diagram of a chloroplast cell:

  A) Granum

  B) Thylakoid

  C) Stroma

  D) Inner membrane

  E) Outer membrane

  
• In DNA polynucleotides:

  • Complimentary base paring 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 complimentary base paring 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 managable ammounts

  It's soluble meaning that it's rapidly available for biochemical processes.
• Why do we synthesise such a large ammount 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 managable 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

  1. It's a polymer of nucleotides;
  2. each nucleotide is formed from deoxyribose, a phosphate group and a nitrogenous base;
  3. there are phosphodiester bonds between nucleotides;
  4. double helix strands are held by hydrogen bonds;
  5. which are between adenine, thymine, cytosine and guanine.
• RNA polynucleotides:

  • Complementary base paring 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 thier 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.