Bioc 2580 Midterm Examination with
Guaranteed Pass Solutions (2025)
Updated.
very non-polar side chains - Answer ala, val, leu, ile, met, phe
- side chains are dominated by non-polar and hydrophobic hydrocarbons
moderately non-polar - Answer gly, cys, pro, tyr, trp
-gly: single H, not enough to be very non-polar
-cys: slightly polar SH
-pro: side chain links to N and alpha C, polar non moderates non-polar hydrocarbon
-tyr & trp: single polar group that partly offsets very non-polar benzene
polar uncharged - Answer ser, thr, asn, gln
-ser & thr: side chains with OH
asn & gln: polar amide groups
-don't hain or lose H+ in aqueous solution at pH 7, so they're uncharged
-good H bond acceptors
very polar positively charged - Answer His, lys and arg
- contain weak bases that gain H+
-charge makes them very polar, overriding non-polar hydrocarbons
very polar negatively charged - Answer -have carboxylic acid groups that lose H+
henderson-hasselbalch equation - Answer pH=pKa+log [deprotonated] / [protonated]
deprotonated - Answer pH is one unit higher than pKa
protonated - Answer pH is one unit below pKa
, -nonpolar AA spend more time in solvent and move almost as fast as solvent
thin layer chromatography - Answer -silica gel is spread in a thin layer on a plastic sheet, this is
the polar stationary phase
-samples are applied to lower edge and placed in solvent
-solvent soaks up sheet and non-polar AA move with the solvent
-highest point reached by solvent is the solvent front
-relative mobility: RF=XB (distance travelled by sample) / XF(distance travelled by solvent
-nonpolar AA have high RF (mobile)
-polar AA have low RF (stationary)
column chromatography - Answer -sample is added
-buffer is added, carrying sample out
-contents of collection is analysed and plotted
-volume of buffer needed to move a component through the column is the elution volume
-highest elution volume=took longest to come out (most polar, bonded to gel)
ninhydrin - Answer -detects AA
-react with primary and secondary amines
-gives a purple colour
ion exchange chromatography - Answer -separates based on charge
-uses charged resins as stationary phase
-cation exchange: contains negative groups that bind positive molecules
-anion exchange: contains positive groups that bind negative molecules
-elution by adding high ion concentration that displaces amino acid from resin or by changing
the pH to alter the charge on the AA so it no longer binds
-net charge determines how strongly each AA binds
metal affinity chromatography - Answer -protein is artificially produced by inserting its gene
into cells, gene can be modified to include extra His residues (his-tag)
-His tag proteins bind tightly to Ni2+ chelating resin
Guaranteed Pass Solutions (2025)
Updated.
very non-polar side chains - Answer ala, val, leu, ile, met, phe
- side chains are dominated by non-polar and hydrophobic hydrocarbons
moderately non-polar - Answer gly, cys, pro, tyr, trp
-gly: single H, not enough to be very non-polar
-cys: slightly polar SH
-pro: side chain links to N and alpha C, polar non moderates non-polar hydrocarbon
-tyr & trp: single polar group that partly offsets very non-polar benzene
polar uncharged - Answer ser, thr, asn, gln
-ser & thr: side chains with OH
asn & gln: polar amide groups
-don't hain or lose H+ in aqueous solution at pH 7, so they're uncharged
-good H bond acceptors
very polar positively charged - Answer His, lys and arg
- contain weak bases that gain H+
-charge makes them very polar, overriding non-polar hydrocarbons
very polar negatively charged - Answer -have carboxylic acid groups that lose H+
henderson-hasselbalch equation - Answer pH=pKa+log [deprotonated] / [protonated]
deprotonated - Answer pH is one unit higher than pKa
protonated - Answer pH is one unit below pKa
, -nonpolar AA spend more time in solvent and move almost as fast as solvent
thin layer chromatography - Answer -silica gel is spread in a thin layer on a plastic sheet, this is
the polar stationary phase
-samples are applied to lower edge and placed in solvent
-solvent soaks up sheet and non-polar AA move with the solvent
-highest point reached by solvent is the solvent front
-relative mobility: RF=XB (distance travelled by sample) / XF(distance travelled by solvent
-nonpolar AA have high RF (mobile)
-polar AA have low RF (stationary)
column chromatography - Answer -sample is added
-buffer is added, carrying sample out
-contents of collection is analysed and plotted
-volume of buffer needed to move a component through the column is the elution volume
-highest elution volume=took longest to come out (most polar, bonded to gel)
ninhydrin - Answer -detects AA
-react with primary and secondary amines
-gives a purple colour
ion exchange chromatography - Answer -separates based on charge
-uses charged resins as stationary phase
-cation exchange: contains negative groups that bind positive molecules
-anion exchange: contains positive groups that bind negative molecules
-elution by adding high ion concentration that displaces amino acid from resin or by changing
the pH to alter the charge on the AA so it no longer binds
-net charge determines how strongly each AA binds
metal affinity chromatography - Answer -protein is artificially produced by inserting its gene
into cells, gene can be modified to include extra His residues (his-tag)
-His tag proteins bind tightly to Ni2+ chelating resin
