Biological Molecules 4: Proteins Flashcards
What are amino acids?
Monomers that make up proteins and peptides
How many naturally occuring amino acids are there?
20
What are zwitterions?
Formed by amino acids in solution by deprotonation of the acid group and protonation of the amine group
(i.e. forms COO- and NH3+)
What is the configuration of all natural amino acids?
The L configuration
Corresponds to R-stereochemistsry
How many aliphatic amino side chains are there?
Six
Glycine (Gly)
Alanine (Ala)
Valine (Val)
Leucine (Leu)
Isoleucine (Ile)
Proline (Pro)
Generally hydrophobic but have different degrees of steric bulk
Proline has an unusual structure comparatively
How many carboxylic acid side chains are there?
Two
Aspartate (Asp)
Glutamate (Glu)
How many amide side chains are there?
Two
Asparagine (Asn)
Glutamine (Gln)
How many aromatic side chains are there?
Four
Histidine (His)
Tryptophan (Trp)
Phenylalanine (Phe)
Tyrosine (Tyr)
How many alcoholic side chains are there?
Two
Serine (Ser)
Threonine (Thr)
How many strongly basic side chains are there?
Two
Arginine (Arg)
Lysine (Lys)
How many sulfur-containing amino acids are there?
Two
Cysteine (Cys)
Methionine (Met)
What is the 21st amino acid?
Selenocysteine
Very rare
Has its own RNA codon specific to some organisms
How is a peptide bond formed?
Between 2 amino acids
Peptide bonds replace the ammonium and carboxylate ionic groups
Resultant chain is not charged but is capable of hydrogen bonding
Also very resistant to degradation (i.e. keratin)
Can be hydrolysed by strong bases or acids
Describe what occurs during transcription.
DNA can be transcribed into mRNA
mRNA used as template for protein amino acid sequence (translation)
Sequence is the protein primary structure
The N-terminous forms the start of the chain and extension occuts at the C-terminous
What is the primary protein structure?
Sequence of amino acids joined by peptide bonds