ACS Biochemistry Practice Final, FGCU, Beharry, Coticone With Complete Solution 2024

1. A weak acid, HA, has a pKa of 4.11. a) At pH 7.11, what will the ratio of conjugate base to acid be? (Henderson-Hasselbach equation: pH=pKa + log [A-]/[HA]) b) Based on answer to "a," is there more HA or A- at that pH? c) At pH 2.11, what will the ratio of conjugate base to acid be? d) Based on answer to "c," is there more HA or A- at that pH? e) At pH 4.11, what will the ratio of conjugate base to acid be? f) Fill in the blank: if pH is greater than the pKa of a weak acid, there will be ___ A- relative to HA. If the pH is less that the pKa of a weak acid, there will be __ A- relative to HA. If the pH=pKa, there will be ___ of A- and HA. - a) 7.11=4.11+log[x] 3=log[x] 1000=x b) A- c) 2.11=4.11+log[x] -2=log[x] 0.01=x d) HA e) 1 f) more; less; the same amount 2. a) Which amino acids would be charged at pH 7? b) which amino acids from "a" would be negatively charged? c) which amino acids from "a" would be positively charged? - a) Asp, Glu, Arg, His, Lys b) Asp, Glu c) Arg, His, Lys 3. Which of the following sequences is most likely to be in the interior core of a globular protein? Why? a) ITFWLI b) IKFGVA c) DKYPGE d) MPCDNA - A; because no charged amino acids and highest % of nonpolar 4. How are beta sheets stabilized in proteins? - Hydrogen bonding between peptide backbone groups? 5. Compare fibroud proteins such as keratin and globular proteins: a) Water solubility b) flexible secondary structure c) highly repetitive primary structure d) size and ability to associate into larger structures - a) fibrous: insoluble globular: soluble b) fibrous: no globular: yes c) fibrous: yes globular: not necessarily d) fibrous: elongated structrue; two alpha keratin polypeptides, each of which form an alpha helix, twisting around each other to form a left-handed coil globular: varies 6. A mixture of proteins was separate on a gel filtration column using a pH 7 buffer. Using the info below, put them in order of elution (first to last) Protein A: MW 27kDa, pI 2 Protein B: MW 144kDa, pI 11 Protein C: MW 43kDa, pI 9 - bca 7. Draw the Michaelis-Menten and double reciprocal plot for an enzyme without inhibitor and with a competitive inhibitor (LABEL axes). Label where Vmax is on each plot. Does VMax change with inhibitor? If so, how? - Vmax doesn't change. 1st: rate of reaction on Y, substrate concentration on X (no inhibitor gets to max rate of reaction at a lower concentration than competitive inhibitor) 2nd: 1/[V0] on Y and 1/[S] on X (competitive inhibitor steeper than no inhibitor) 8. a) calculate the catalytic efficiency for each of the substrates (A-D) A) Km=1uM; kcat=0.5 1/s B) Km=2um: kcat=0.1 1/s C) Km=10uM; kcat=1 1/s D) Km=20uM; kcat=20 1/s b) Which is the best substrate? - a) A= 0.5/uMs B= 0.05/uMs C=0.1/uMs D=1/uMs b) D (highest value) 9. a) Draw the binding curve for a protein that exhibits copperativity such as hemoglobin.