1.1 Amino Acids Found in Proteins [HY] Flashcards
All AA’s are optically active/ have a chiral center except?
Glycine, which has a hydrogen atom as its R group, making it achiral
All AA’s have a S configuration except?
Cysteine, has an (R) absolute
configuration because the −CH2SH group has priority over the −COOH group
What affect does proline’s ring have on it?
That ring places notable constraints on the flexibility of
proline, limiting where it can appear in a protein and can have significant effects on proline’s role in secondary structure.
Why are the polar AA’s polar?
B/c of the OH side chains, and therefore able to participate in hydrogen bonding.
Why is Sulfur on cysteine more likely to be oxidized?
- sulfur is larger than oxygen, the S−H bond is longer and weaker than the O−H bond
- Oxygen is more electronegative than Sulfur
What is physiological pH?
7.4
How do most acids exist in cells?
In the deprotonated form
Why are positive AA’s positive?
have side chains that have positively charged nitrogen atoms.
Which AA’s are hydrophobic?
- A, I, L, V, F
- Most likely in interior of proteins
Which AA’s are hydrophilic?
- All positive AA’s (H, R, K)
- Anions of D & E (aspartate, glutamate)
- Amides: N & Q
Which AA’s are on the surface of proteins?
- AA’s with charged side chains
What is notation for substitution?
- [Letter of initial AA] [AA #] [Letter of final AA]