Organic Chemistry (8th Edition)
8th Edition
ISBN: 9780134066639
Author: Bruice
Publisher: PEARSON
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Chapter 21, Problem 77P
A chemist wanted to test his hypothesis that the disulfide bridges that form in many proteins do so after the minimum energy conformation of the protein has been achieved. He treated a sample of an enzyme that contained four disulfide bridges with 2-mercaptoethanol and then added urea to denature the enzyme. He slowly removed these reagents so that the enzyme could re-fold and re-form the disulfide bridges. The enzyme be recovered had 8o% of its original activity. What would be the percent activity in the recovered enzyme if disulfide bridge formation were entirely random rather than determined by the tertiary structure? Does this experiment support his hypothesis?
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A chemist wanted to test his hypothesis that the disulfide bridges that form in many proteins do so after the minimum energy conformation of the protein has been achieved. He treated a sample of an enzyme that contained four disulfide bridges with 2-mercaptoethanol and then added urea to denature the enzyme. He slowly removed these reagents so that the enzyme could re-fold and re-form the disulfide bridges. The enzyme he recovered had 80% of its original activity. What would be the percent activity in the recovered enzyme if disulfide bridge formation were entirely random rather than determined by the tertiary structure? Does this experiment support his hypothesis?
How does the near attack conformation (NAC) contribute to enzyme function?
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Chapter 21 Solutions
Organic Chemistry (8th Edition)
Ch. 21.1 - a. Explain why, when the imidazole ring of...Ch. 21.2 - a. Which isomer(R)-alanine or (S)-alanineis...Ch. 21.2 - Prob. 4PCh. 21.3 - Prob. 5PCh. 21.3 - Prob. 6PCh. 21.3 - Draw the predominant form for glutamate in a...Ch. 21.3 - a. Why is the pKa of the glutamate side chain...Ch. 21.4 - Calculate the pI of each of the following amino...Ch. 21.4 - a. Which amino acid has the lowest pI value? b....Ch. 21.4 - Prob. 12P
Ch. 21.4 - Prob. 13PCh. 21.4 - Explain why the pI of lysine is the average of the...Ch. 21.5 - What aldehyde is formed when valine is treated...Ch. 21.5 - Prob. 16PCh. 21.5 - Prob. 17PCh. 21.5 - Prob. 18PCh. 21.5 - Prob. 19PCh. 21.6 - Why is excess ammonia used in the preceding...Ch. 21.6 - Prob. 21PCh. 21.6 - What amino acid is formed using the...Ch. 21.6 - Prob. 23PCh. 21.6 - What amino acid is formed when the aldehyde used...Ch. 21.7 - Esterase is an enzyme that catalyzes the...Ch. 21.8 - Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate...Ch. 21.8 - Draw the resonance contributors of the peptide...Ch. 21.8 - Which bonds in the backbone of a peptide can...Ch. 21.9 - An opioid pentapeptide has the following...Ch. 21.9 - What is the configuration about each of the...Ch. 21.9 - Glutathione is a tripeptide whose function is to...Ch. 21.10 - What dipeptides would be formed by heating a...Ch. 21.10 - Suppose you are trying to synthesize the dipeptide...Ch. 21.10 - Show the steps in the synthesis of the...Ch. 21.10 - a. Calculate the overall yield of bradykinin when...Ch. 21.11 - Show the steps in the synthesis of the...Ch. 21.13 - Prob. 37PCh. 21.13 - In determining the primary structure of insulin,...Ch. 21.13 - A decapeptide undergoes partial hydrolysis to give...Ch. 21.13 - Explain why cyanogen bromide does not cleave on...Ch. 21.13 - Indicate the peptides produced from cleavage by...Ch. 21.14 - Prob. 43PCh. 21.14 - Three peptides were obtained from a trypsin...Ch. 21.14 - Prob. 45PCh. 21.15 - How would a protein that resides in the nonpolar...Ch. 21.16 - a. Which would have the greatest percentage of...Ch. 21.17 - When apples that have been cut are exposed to...Ch. 21 - Glycine has pK2 values of 2.34 and 9.60. At what...Ch. 21 - Prob. 50PCh. 21 - A titration curve is a plot of the pH of a...Ch. 21 - Prob. 52PCh. 21 - Aspartame (its structure is on page 1007) has a pl...Ch. 21 - Draw the form of aspartate that predominates at...Ch. 21 - Show how phenylalanine can be prepared by...Ch. 21 - A professor was preparing a manuscript for...Ch. 21 - What aldehydes are formed when the following amino...Ch. 21 - Prob. 58PCh. 21 - Determine the amino acid sequence of a polypeptide...Ch. 21 - Prob. 60PCh. 21 - Prob. 61PCh. 21 - Which is the more effective buffer at...Ch. 21 - Identify the location and type of charge on the...Ch. 21 - Draw the product obtained when a lysine side chain...Ch. 21 - After the polypeptide shown below was treated with...Ch. 21 - Treatment of a polypeptide with 2-mercaptoethanol...Ch. 21 - Show how aspartame can be synthesized using DCCD.Ch. 21 - -Amino acids can be prepared by treating an...Ch. 21 - Reaction of a polypeptide with carboxypeptidase A...Ch. 21 - a. How many different octapeptides can be made...Ch. 21 - Glycine has pKa values of 2.3 and 9.6. Do you...Ch. 21 - A mixture of 15 amino acids gave the fingerprint...Ch. 21 - Write the mechanism for the reaction of an amino...Ch. 21 - Prob. 74PCh. 21 - Show how valine can be prepared by a. a...Ch. 21 - The primary structure of -endorphin, a peptide...Ch. 21 - A chemist wanted to test his hypothesis that the...Ch. 21 - Propose a mechanism for the rearrangement of the...Ch. 21 - A normal polypeptide and a mutant of the...Ch. 21 - Determine the amino acid sequence of a polypeptide...
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- 22-49 Based on your knowledge of the chemical properties of amino acid side chains, suggest a substitution for leucine in the primary structure of a protein that would probably not change the character of the protein very much.arrow_forward22-61 Polyglutamic acid (a polypeptide chain made only of glutamic acid residues) has an a-helix conformation below pH 6.0 and a random-coil conformation above pH 6.0. What is the reason for this conformational change?arrow_forwardAlthough RNA is single-stranded, the strand sometimes folds back on itself to give a complementary portion. What would be the complementary portion of the RNA fragment having the bases uracil-cytosine-guanine? A virus is a particle that contains DNA or RNA that is surrounded by a coat of protein that can replicate only in a host cell. The influencza virus shown in this electron microscope image is an RNA virus.arrow_forward
- A 1.00-mg sample of a pure protein yielded on hydrolysis 0.0165 mg of leucine and 0.0248 mg of isoleucine. What is the minimum possible molar mass of the protein? (MMleucine=MMisoleucine=131g/mol)arrow_forwarda. How many different proteins (in terms of sequence) can you make if the protein is five amino acids long and consists of Phe, Ser, Ala, Pro, and Glu and you can use any of these five amino acids as many times as you want? b. How many different proteins can be made for the five amino acids listed in part a but you can only use each of them one time?arrow_forwardWhich amino acids have R groups with an additional chiral carbon? - Cysteine - Isoleucine - Threonine -Histidine - Tryptophan - Tyrosine - Methioninearrow_forward
- Although the bond energy for the hydrogen bond in a vacuum is estimated to be about 20 kJ/mol, we find that each hydrogen bond in a folded protein contributes much less--probably less that 5 kJ/mol--to the enthalpy of protein stabilization. Suggest an explanation for this difference. Explain briefly.arrow_forwardHow can the Michaelis constant (Km) be identified and used to represent the affinity between the enzyme and the substrate?arrow_forward1.What makes ionic bonds different from covalent bonds? Explain with respect to the bond formation between MgCl2 and N2. 2. A group of young researchers was working on a biochemical pathway. At that time, they produced an enzyme having altered active site. Do you think, the activity of the new enzyme would differ from the original one? Why? On a different reaction they found, an enzyme works best at a temperature near about 30 degree Celsius. At 60 degree Celsius, the enzyme becomes inactivated. Briefly explain, why that enzyme is not working at elevated temperature?arrow_forward
- What is an antioxidant enzyme? Why is catalase considered to be an antioxidant enzyme?arrow_forwardDescribe two examples of protein folding patterns and identify what level of protein structure they belong to. What other reagents might you use besides ferric chloride to test affinity for metal ions? How many grams of the protein are in one 200 g glass of milk?arrow_forwardA peptide has the sequence Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly The p?a values for the peptide’s side chains, terminal amino groups, and carboxyl groups are provided in the table. Amino acid Amino pKa Carboxyl pKa Side‑chain pKa glutamate 9.609.60 2.342.34 4.254.25 histidine 9.179.17 1.821.82 6.006.00 tryptophan 9.399.39 2.382.38 serine 9.159.15 2.212.21 glycine 9.609.60 2.342.34 leucine 9.609.60 2.362.36 arginine 9.049.04 2.172.17 12.4812.48 proline 10.9610.96 1.991.99 Calculate the net charge of the molecule at pH 11 and estimate the isoelectric point (pI)(pI) for this peptide.arrow_forward
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