Unit 2 Flashcards
(13 cards)
How are amino acids linked?
Amino acids are covalently linked together through amide (peptide) bonds to form proteins (polypeptides)
Peptides vs Proteins
- Peptides
- Short polypeptides
- Usually less than 40 amino acids in length
- Proteins
- Longer polypeptides
- Usually more than 40 amino acids in length
What is the driving force for a proteins three dimensional shape?
Hydrophobic so the amino acids tend to cluster in the interior of a protein
What does chiral mean?
Non-superimposable on its mirror image
Humans have L amino acids
What is fluorescence stimulated by
By absorption of blue light by a tripetide chromophore in GFP
Blue light in jellyfish light organ is another bioluminescent protein called aequorin that emits light following calcium binding
What is the isoelectric point pI
The pH at which the charge of the amino acid is neutral
What is a zwitterion
Molecule a positive (amino) and negative (carboxyl) groups that is electrically neutral
What is pKa and what does it change
pKa: the pH at which the side chain is ionized, it changes depending on the local chemical environmenty
How do peptide bonds formed and how can they break apart
Peptide bonds are formed by condensation between the amine and carboxylic acid groups (water is the product)
It is catalyzed by RNA component of ribosomes
Hydrolysis breaks apart the peptide bond (enzymatic assisred by proteases)
What is the beginning of the protein called vs the end of the protein
N-(amino) terminus: at the beginning of the protein
C- (carboxy) terminus: at the end of the protein
What is important for the peptide bonds having partial double bond character
- The peptide bond is planar, this means that there is no rotation about the peptide bond
- There are two resonance forms that are possible
- Two bonds in the peptide backbone can rotate: Phi (N-C, amide nitrogen and the carbon), Psi (C-C, carbon and the carbonyl carbon)
Each amino acid has a phi and psi set of angles
