Week 3 Amino acids

• What are the 4 major classes of biomolecules?

  • Amino acids and proteins
  • Nucleotides and nucleic acids (dna and rna)
  • Carbohydrates
  • Lipids
• What are macromolecules?

  monomers that join together to form a polymer

  • Amino acids are monomers of proteins
  • Nucleotides are monomers of nucleic acids
  • Sugar is a monomer of complex carbs
• Amino acids and proteins:

  20 different amino acids and 50 - 2000 proteins

  Proteins have many functions

  • Hormones
  • Antibodies
  • Muscle fibres
  • Oxygen transport
  • Ion channels
  • Enzymes
• Structure of an amino acid:

  A) carboxyl

  B) amino

  C) R

  
• Naming carbon atoms in carboxylic acids

  A) alpha

  B) beta

  C) gaba

  D) delta

  
• Which functional group accepts electrons and what does it change to?

  NH2 accepts electrons

  • NH2 becomes NH3+
• Which functional group donates electrons and what does it change to?

  COOH donates electrons

  • COOH becomes COO-
• General structure of amino acids

  • Alpha carbon always has 4 subsituents and has a tetrahedral shape
  • They all have (except proline)
  • Acidic carboxyl
  • Basic amino
  • Hydrogen connected to alpha carbon
  • R group is unique
• Isomer - same formula but different chemical structure
• Stereoisomer - same molecular formula and the same bonding but different three-dimensional orientation of atom
• Enantiomers - stereoisomers that are non-superimposable mirror images
• Chiral carbon atom - carbon atom that has 4 different groups bonded to it
• Chiral carbons:

  • Amino acids are chiral (except glycine)
  • Have L and D forms
  • Proteins only have L amino acids
• The 20 amino acids:

  A) Alanine

  B) Glutamine

  C) Histidine

  D) Lysine

  E) Methionine

  F) Tryptophan

  
• Amino acid classification is split into 5 groups, which are?

  Nonpolar, aliphatic

  Aromatic

  Polar, uncharged

  Postively charged

  Negatively charged
• Nonpolar, aliphatic:

  Glycine - has a single hydrogen

  Alanine - has a methyl group

  Proline - (slightly odd) has a branch and it has a carbon group covalently bonded to the NH2

  Rest - they are branched, so just need to know side chain and that they are hydrophobic

  Methionine - has a Sulphur atom
• Guess the nonpolar, aliphatic amino acids:

  A) glycine

  B) alanine

  C) proline

  D) valanine

  E) leucine

  F) isoleucine

  G) Methionine

  
• Aromatic (contain benzene ring)

  Phenylalanine - methyl and benzene

  Tyrosine - benzene and hydroxyl group

  Tryptophan - most complex
• Guess the aromatic amino acids:

  A) Phenylalanine

  B) Tyrosine

  C) Tryptophan

  
• Positively charged

  Lysine - has long chain plus 2 N's

  Arginine - has 4 N's

  Histidine - has a ring structure
• Guess the positively charged amino acids:

  A) lysine

  B) Histidine

  C) arginine

  
• Negatively charged:

  Asparate - has a methyl and COO -

  Glutamate - has 2 methyl and a COO-
• Guess the negatively charged amino acids:

  A) Aspartate

  B) Glutamate

  
• Polar, non charged:

  Serine - one methyl and a hydroxyl group

  Threonine - two methyls and a hydroxyl group

  Cysteine - 2nd amino acid with a sulphur

  Asparagine - one methyl plus amide group

  Glutamine - two methyl plus amide group
• Guess the polar, non charged amino acids:

  A) serine

  B) threonine

  C) cysteine

  D) asparagine

  E) Glutamine

  
• Glutamate, glutamic acid anf glutamine:

  Glutamate has COO- on R side chain

  Glutamic acid has a COOH on R side chain

  Glutamine has an amine (CO-NH) on R side chain
• Identify glutamate, glutamine and glutamic acid:

  A) glutamic acid

  B) glutamate

  C) Glutamate

  D) Glutamine

  
• Peptide bonds:

  • form between CO and NH
  • water is lost

  
• Bronstead-Lowery definitions:

  • Acids = proton donators (H+)
  • Bases = proton acceptors
• Acid Dissociation Constant:

  A) higher

  B) -log

  C) lower

  D) HA

  
• Titration curve 1

  A) Buffering region

  B) pH

  C) H+

  
• Titration curve and pKa of acids

  A) midpoint

  B) buffering regions

  
• Buffers:

  • Almost all biological processes are pH-dependent
  • Small changes in pH can produce large changes in rate of processes
  • Buffer solution tends to resist pH changes when small amount of acids or bases are added
  • Buffers are mixtures of weak acids and their conjugate bases
• Amino acids x acids and bases:

  • They can act as acids or bases
  • Amino acids have zwitterions
  • Acid - donate protons from carboxyl group
  • Base - accept protons at amine group

  
• Charge of amino acids:

  A) zwitterionic

  B) protonated

  C) +1

  D) 0

  E) -1

  
• Titration curve of an amino acid

  A) -1

  B) 0

  C) +1

  D) zwitterion

  
• Isoelectric point - pH at which net charge is zero

  
• Negatively charged R groups:

  A) Aspartate

  B) Glutamate

  
• Positively charged R groups

  A) lysine

  B) arginine

  C) histidine

  
• Peptide ends are not the same:

  A) N

  B) C