Lecture 4: Amino Acids Flashcards
What are the building blocks of proteins?
Amino Acids
What defines the AA type?
Side chain!
Label the AA:
An ampholyte molecules contains both ____ and _____ groups and will exist mostly as ________ in a certain range of pH.
An ampholyte molecules contains both acidic and basic groups and will exist mostly as zwitterions in a certain range of pH.
What is the Zwitterionic form?
Which is acid and base?
What is the charge on an amino acid dependent upon?
At a low pH, where is a proton removed from first?
And which is the zwitterion?
The charge on an amino acid is dependent on the pH of the solution.
Carboxyl group
The neutral form bw
At the isoelectric point, what is equal to eachother making the average charge 0?
pI = pH
For the isoelectric point of Amino Acids, what involves the net zero charge species?
Two equilibrium dissociation reactions
At what point in a titration curve will amino acids will have the greatest species and how do you calculate it?
Midpoint bw 2 groups –> Isoelectric point
2 Henderson-Hasselbalch equations can be averaged together
What defines amino acids?
Side chains!
__ “common” AA’s found in _______.
When are they modified?
20“common” AA’s found in proteins.
Modified after translation
What is the simplest AA?
D/L?
Glycine! R = H
Neither! Achiral
What ways are AA’s classified?
- ___ & ____
- ?
- ?
- ________/________ (either ____/_____ water)
- ? (_____ interactions)
- ? (determined by ___ _____)
- ________ to adopt a particular __________ in ____ (combo of above)
- Size & Shape
- Charge(s)
- Polarity
- Hydrophilicity/Hydrophobicity (either attracts/excludes water)
- Aromaticity (stacking interactions)
- Confirmation (determined by side chain)
- Propensity to adopt a particular confirmation in proteins (combo of above)
What is the molecular asymmetry of an AA?
Degree of torsion?
What are the two types?
Tetrahedral carbon atom w/ 4-substituent groups
109.5º
- Chiral = 4 diff groups
- Achiral = 2/4 groups are the same
What are the stereoisomers of alpha AA’s?
Name the structures with the appropriate stereochemistry.
L (Amine group is on the left) & D
What AA contains Disulfide bonds?
What is the AA after oxidation?
What are the properties of this AA?
Non-polar and strongly hydrophobic
What detects the presence of particular biomolecules and estimates concentration?
Label the image.
Spectrophotometer
When labeling AA’s what is the convention?
Label the structure.
What occurs when there is ambiguity?
Start with the most oxidized (Usually Carboxyl of AA)
then count by numbers of Greek letters
DOuble lettering/numbering occurs w/ ambiguity
