amino acids, proteins and DNA

• What is an amino acid?


  An amino acid is a compound with an amine group and a carboxylic acid group.
• Where is the amine group located in an amino acid?


  The amine group is always on the second carbon in the chain.
• What are amino acids also known as due to their structure?


  Amino acids with this structure are also known as '𝛼-amino acids'.
• Why is the second carbon in amino acids often chiral?


  It is chiral because it has four different groups bonded to it.
• What does it mean for amino acids to exist as optical isomers?


  It means they can exist in different enantiomeric forms.
• What is the common form of amino acids found in nature?


  Nearly all amino acids exist as a single negative enantiomer.
• How do amino acids react in acidic conditions?


  In acidic conditions, the lone electron pair is more likely to accept a hydrogen atom, producing a positive end.
• What happens to amino acids in basic conditions?


  In basic conditions, the hydrogen atom on the -OH group is more likely to be lost, producing a negative end.
• What is a zwitterion?


  A zwitterion forms when the overall pH of the molecule is zero, known as the isoelectric point.
• How can thin-layer chromatography be used with amino acids?


  Thin-layer chromatography can identify unknown amino acids using UV light to view traces on the silica plate.
• What are proteins made of?

  Proteins are sequences of amino acids joined together by peptide links.
• What process can reverse the formation of proteins?


  The reaction can be reversed by boiling the protein in 6.0 moldm^-3 HCl for 24 hours in a process called hydrolysis.
• How is hydrolysis of proteins typically carried out in nature?


  In nature, hydrolysis is carried out by enzymes so harsh conditions are not required.
• What are the different structures of proteins?

  • Primary Structure: a single polypeptide chain of amino acids.
  • Secondary Structure: an α-helix or β-pleated sheet held with hydrogen bonds.
  • Tertiary Structure: chains folded into a 3D coil with hydrogen and disulfide bonding.
• What are disulfide bridges in proteins?


  Disulfide bridges are sulfur-sulfur bonds that hold together tertiary structures and keep the protein stable.
• What is the role of enzymes?


  Enzymes act as biological catalysts.
• What is the structure of enzymes?


  Enzymes have a tertiary structure that contains active sites specific to certain substrates.
• What does it mean for enzymes to be stereospecific?


  It means they can only break down a single enantiomer and will have no effect on the other optical isomer.
• What is DNA?

  DNA (deoxyribonucleic acid) is a condensation polymer formed from a sugar, a phosphate, and a base.
• What is a nucleotide?


  A nucleotide consists of one sugar, one phosphate, and one base.
• What sugar is present in DNA nucleotides?

  The sugar present in DNA is 2-deoxyribose.
• What forms the sugar-phosphate backbone of DNA?

  Sugar-phosphate bonds hold together multiple nucleotides into a polynucleotide strand.
• What are the four possible bases in DNA nucleotides?

  • Adenine
  • Cytosine
  • Thymine
  • Guanine
• How do bases pair in DNA?


  Bases pair up in specific complementary pairs via hydrogen bonding.
• What are the complementary base pairs in DNA?

  Guanine and Cytosine bond with three hydrogen bonds; Thymine and Adenine bond with two hydrogen bonds.
• What is cisplatin used for?


  Cisplatin is used as an anticancer drug.
• What is the structure of cisplatin?


  Cisplatin is the cis isomer of a square planar complex of platinum.

  
• Why is only the Z-isomer of cisplatin effective?


  Only the Z-isomer is effective because cells in the natural world are chiral.
• How does cisplatin prevent cancer from spreading?


  Cisplatin bonds to strands of mutated DNA to prevent it from replicating via ligand replacement with guanine.
• What are the side effects of cisplatin?


  Cisplatin can bond to heated DNA strands causing serious side effects such as hair loss.
• How is cisplatin administered to reduce side effects?


  Cisplatin is administered in small amounts to try and reduce side effects.
• Why is cisplatin still used despite its side effects?


  The long-term benefits of using cisplatin and its effectiveness as an anticancer drug mean it continues to be used.