Amino Acids

Question 1

What are Amino Acids?

Answer 1

• They are Bi-functional organic molecules with both the COOH and NH₂
  functional groups.
• Building blocks for proteins
• There are 20 amino acids

Question 2

Why do Amino Acids have both acidic and basic properties?

Answer 2

• The COOH acts as a acid by releasing H⁺
• The NH₂ acts a base by accepting H⁺
• Amino Acids exist as Zwitterions. At PH 7, they have a permanent positive and negative charge but are neutral overall.

Question 3

What are peptides?

Answer 3

• A compound formed from multiple Amino acids
• 2 Amino acids can undergo a Condensation reaction to form a
  Dipepetide.
• ≤ 50 amino acids = polypeptide
• ≥ 50 amino acids = protein

Question 4

Describe how Amino Acids form proteins?

Answer 4

• Amino acids join via an amide link ( - CONH)

- AKA peptide bond

Question 5

Describe the primary, secondary, and tertiary structures of proteins?

Answer 5

• Primary structure = The chain of amino acids, held together by covalent bonds of the peptide linkage
• Secondary structure = folding of primary structure into, Either, α-helix or β-pleated sheet, held in place by hydrogen bonds.
• Tertiary structure = The 3D shape, held together by hydrogen bonding, ionic bonding and Disulfide bonds.

Question 6

What bonds hold protein molecules in their particular

shapes?

Answer 6

Primary Structure = Covalent Bonds
Secondary structure = Hydrogen bonding
Tertiary structure = Hydrogen bonding, Ionic bonding, Disulfide bonding

Question 7

Describe how proteins can be broken down?

Answer 7

• The Secondary structure can be broken by heating or change in PH.
• Primary structure can be broken down by refluxing with HCL.

Question 8

What is an enzyme?

Answer 8

• Biological Catalysts with protein structure that speed up reactions
• Enzymes have an active site with a shape specific to its substrate.
• They can denature by PH / Temp change.

Question 9

Describe Enzyme action?

Answer 9

• Enzymes attract the substrate onto its active site where the substrate
  will fit onto the active site.
• Substrate broken down into products
• Products are released.

Question 10

What is a nucleotide?

Answer 10

• A building block of DNA
• Contains a sugar a phosphate and an organic base.
• 4 Types: Adenine, Cytosine, thymine, Guanine

Question 11

Describe how nucleotides bond together to form a

single strand of DNA?

Answer 11

• The OH group of the phosphate in 1 molecule reacts with the OH group on the sugar of another molecule.
• Water is eliminated

Question 12

Describe how complementary strands of DNA are formed?

Answer 12

• Each base can hydrogen bond to its complementary bases
• Adenine to Thymine
• ## Cytosine to Guanine

Question 13

Describe how the anti-cancer drug cisplatin works?

Answer 13

• Cisplatin is a molecule with the formula Pt(NH₃)₂Cl₂. It
  bonds to strands of DNA distorting their shape. This prevents the
  replication of the cell.
• Dative covalent bonds will form between the lone pair of electrons on
  the nitrogen atoms of the guanine, and the platinum of the cisplatin. The
  chloride ions are replaced.
• This is a ligand substitution reaction.

Question 14

Why do Amino acids have a high boiling and melting point?

Answer 14

Zwitterions have strong ionic bonds between them.

Question 15

Why do all amino acids except Glycine display Optical isomerism?

Answer 15

• Amino acids except have 4 groups attached to a chiral carbon atom.
• They can arrange themselves in 2 different ways to create 2 mirror images which cannot be superimposed.
• Glycine has no chiral carbon.