Hey all thank you for helping me out with this problem set...I am really confuse
ID: 845450 • Letter: H
Question
Hey all thank you for helping me out with this problem set...I am really confused because my teacher told us to work through these problems before we read the lecture. I would like to check my answers so please provide a correct answer to each question and specify the question anwers you are unsure of. Thanks again!
1.) which of the following amino acids has an uncharged polar side chain at ph 7.0?
a.) Arg b.) Blu c.) Thr d.) Pro e.) lle
2.) The pk1 (alpha-carboxylate), pk2 (alpha amino) and pkr (side chain) for the amino asparatic acid are 2.0, 9.9, and 3.9 respectively. At ph 7.0 asparatic acid would be charged predominately as follows.
a.) alpha carboxylate 0, alpha amino +1, side chain 0, net charge +1
b.) alpha carboxylate -1, alpha amino +1, side chain -1, net charge -1
c.) alpha carboxylate 0, alpha amino -1, side chain 0, net charge -1
d.) alpha carboxylate +1, alpha amino -1, side chain +1, net charge +1
e.) alpha carboxylate -1, alpha amino +1, side chain +1, net charge +3
3.) the secondary structre of a protein is:
a.) the order of amino acids in the protein
b.) the arangement in space of the backbone atoms in the protein
c.) the three dimensional arangement of all atoms in the protein
4.)Quaternary shape is associated with:
a.) overall shape of polypeptide chain
b.) sum of secondary and tertiary interactions
c.) single proteins with one subunit
d.) the interactions of one polypeptide to another polypeptide in a protein with multiple polypeptide chains
5.)the amino acid with imidazole side chain is:
a.) N b.) P c.) H d.) W
6.) Which of the following tripeptides would be expected to be most hydrophobic:
a.) KYG b.) KYA c.) GYA d.) DYA e.) DYG
7.)Which amino acid would most likely be soluble in a nonpolar solvent such as benzene:
a.) Valine b.) histidine c.) glutamine d.) glycine e.) none of above
8.)A protein peptide backbone is mostly extended and hydrogen bonded to different strands of the protein is composed mostly of the ___________ secondary structre:
a.) alpha helix
b.) beta helix
Explanation / Answer
1 - thr - Tyr has a special OH - due to strong electron withdrawing power of ring structure the OH is ionisable so has a pK value. Value is 10.07 so at pH 7.4 not ionised very much. Howevertyr used at active site of some enzymes where localised disturbance of pH can be generated and allow the ionisable OH to participate in catalysis.
2 - B - alpha carboxylate -1, alpha amino +1, side chain -1, net charge -1
3 - B - In proteins, the secondary structure is defined by the patterns of hydrogen bonds between backbone amino and carboxyl groups.
4 - D - The quaternary protein structure involves the clustering of several individual peptide or protein chains into a final specific shape.
5 - Histidine has a nitrogen-containing imidazole ring for a side chain; lysine has a primary amino group on the ?-carbon (from the sequence ?, ?, ?, ?, ?); and arginine has a guanidinium group.
6 - N - proline - phenylalanine - leucine - C
7 - A - Valine
8 - Beta helix