a) If hair grows at a rate of 37 cm per year, then what is the rate of peptide b
ID: 942961 • Letter: A
Question
a) If hair grows at a rate of 37 cm per year, then what is the rate of peptide bond synthesis (peptide bonds per second) that would account for the observed growth of hair? Assume that biosynthesis of alpha-helical keratin chains is the rate-limiting factor for the growth of hair, and use the conversion factors: (one peptide bond/residue) * (3.5 residues/5.4 angstroms). Also, to simplify this problem, consider the growth of one keratin alpha-helix only. Record your answer to the nearest ones.
b) A protein has 10 cysteine residues. How many possible ways are there to form 5 disulfides with these 10 cysteine residues?
c) Assume the earth has 7.3 × 109 people. If, by a miracle, a world of people sprung up for each person, how would this number compare to a mole? In other words, how many times bigger (or smaller) is a mole compared to the “miracle” world described above? Enter your answer to the nearest hundreds.
d)You are performing an assay that requires a radioisotope. The half-life of this isotope is not on the label for some unexplained reason, so you ask a colleague who tells you that in a sample of the same isotope she could only detect 3.125% of the initial radioactivity after 75 days had passed. To the nearest day, what is the half-life of this isotope?
e)Imagine that inside a cell the [creatine phosphate] = 3.5 mM, [creatine] = 0.6 mM, and [Pi] = 4.3 mM. Furthermore, imagine that the pH inside the cell is 7.4. Given that G° for creatine phosphate hydrolysis is -10.3 kcal/mol, what is the G for creatine phosphate hydrolysis inside the above-described cell, which is at 37 °C? Report your answer in kcal/mol to the nearest tenths. Hint: you might wish to consult the chapter in our text that discusses thermodynamics.
Explanation / Answer
If hair grows at a rate of 37 cm per year
(one peptide bond/residue) * (3.5 residues/5.4 angstroms)* (37 cm / 1 year)*(10^8 angstroms/ 1CM)*(1 year / 3.15*10^7)
= 76 peptides bond / sec.
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