This set of Protein Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Chemical Synthesis of Peptides – 1”.
1. Which of the following are long molecular chains that makeup proteins?
a) Lipids
b) Carbohydrates
c) Nucleotides
d) Peptides
View Answer
Explanation: Peptides are the long molecular chains that makeup proteins. Peptides are made up of amino acids that are linked together by a peptide bond. Amino acid chains of length less than 40 amino acids are calledpolypeptide chains.
2. Which of the following is not a use of peptide?
a) Drugs
b) Food supplement
c) Diagnosis of disease
d) Storage of genetic information
View Answer
Explanation: Peptides have many possible benefits as a drug, like it reduces inflammation, improves immune function, and prevents the formation of blood clots. It is also used in the diagnosisof various diseases. Research indicates that collagen peptide supplements can increase muscle mass and strength. Peptide does not store any genetic information.
3. Peptides are very easy to synthesize in the lab.
a) True
b) False
View Answer
Explanation: The above statement is false. Peptides are very difficult to make as the synthetic chemist must ensure that the amino acids that make up the chain are added in the correct order and that they do not undergo any other reactions.
4. Who discovered the process of Solid Phase Peptide Synthesis?
a) Robert Hooke
b) Robert Brown
c) Robert Baratheon
d) Robert Merrifield
View Answer
Explanation: Robert Merrifield discovered the process of Solid Phase Peptide Synthesis. Chemical synthesis of peptides is playing an increasingly important role in protein production, especially after Merrifield innovated SPPS in 1963.
5. What is the first step in the Solid Phase Peptide Synthesis?
a) Protection
b) Deprotection
c) Coupling
d) Attaching an amino acid to the polymer
View Answer
Explanation: The Solid Phase Peptide Synthesis is carried out cyclically. The first step is attaching an amino acid to the polymer; the second step is protection; the third step is coupling; the fourth step is deprotonation, and the last step is polymer removal.
6. With the help of which of the following the amino acid is attached to the polymer support?
a) Building agent
b) Synthesis agent
c) Protecting agent
d) Linkage agent
View Answer
Explanation: The amino acid is attached to the polymer support with the help of a linkage agent. The amino acid is reacted with a molecule known as “linkage agent”, and the other end of the linkage agent is reacted with the polymer support. This enables us to attach the amino acid to the solid polymer.
7. Which of the following amino acid contains side chains that require protection?
a) Glycine
b) Valine
c) Alanine
d) Glutamic acid
View Answer
Explanation: Glutamic acid is the amino acid that contains a side chain that requires protection. The side chains of glycine, valine, and alanine do not require protection. This is because the side chains of the amino acids are non-reactive and thus do not require protection.
8. What is the process in which the basic group of one amino acid and the acidic group of the other are both made unable to react?
a) Desensitization
b) Prohibition
c) Restriction
d) Protection
View Answer
Explanation: The process in which the basic group of one amino acid and the acidic group of the other are both made unable to react is called protection. This deactivation is known as the protection of reactive groups and a group that is unable to react is called a protected group.
9. Strong acids and bases are used in the peptide synthesis.
a) True
b) False
View Answer
Explanation: The above statement is false. The bonds between amino acids are called amide bonds. These are strong bonds but they can be hydrolyzed by either strong acid or strong base. Thus, only neutral substances and weak acids and bases can be used in peptide synthesis.
10. Peptide synthesis is a very time-consuming process.
a) False
b) True
View Answer
Explanation: The above statement is true. Peptide synthesis is a very time-consuming process. It involves adding one amino acid, washing away any unreacted acids, and then adding the next amino acid and so on. Thus, it is a time-consuming process and gives very low yields.
11. There are no environmental implications for the SPPS method.
a) True
b) False
View Answer
Explanation: The above statement is false. SPPS, like much of organic chemistry, makes use of organic solvents that are hazardous to the environment. Thus, ways of producing peptides in aqueous or partially aqueous (e.g. water/ethanol mixtures) solutions must be developed to avoid the use of organic solvents.
12. If solutions containing two amino acids are mixed, then how many different dipeptides can be formed?
a) One
b) Two
c) Three
d) Four
View Answer
Explanation: If solutions containing two amino acids are mixed, then the number of different dipeptides can be formed is four. E.g. if solutions containing valine and alanine are mixed, the four dipeptides formed would be val-val, val-ala, ala-val, and ala-ala. Moreover, other longer peptides will also be formed apart from these dipeptides. This can also be calculated by using the formula given below,
Formula: n=xy
Where x=number of different amino acids used,
y=number amino acid positions in the peptides.
Hence, n=22
n=4.
13. Which of the following compound is used to protect the amino side chain of amino acids?
a) 6-fluorenylmethoxycarbonyl
b) 9-fluorenylethoxycarbonyl
c) 6-fluorenylethoxycarbonyl
d) 9-fluorenylmethoxycarbonyl
View Answer
Explanation: 9-fluorenylmethoxycarbonyl is used to protect the amino side chain of amino acids. The amino group of amino acids is protected to prevent the acids from reacting with each other. This is done by protecting it with 9-fluorenylmethoxycarbonyl (FMOC).
14. Amino acids containing aromatic, acidic, basic, or highly polar side chains are likely to be non-reactive.
a) True
b) False
View Answer
Explanation: The above statement is false. Amino acids containing aromatic, acidic, basic, or highly polar side chains are likely to be reactive. These must be protected to prevent the formation of unwanted branched chains.
15. How many combinations of dipeptides can be formed if three solutions of different amino-acids are mixed?
a) Six
b) Sixteen
c) Twenty-seven
d) Nine
View Answer
Explanation: Nine different combinations of dipeptides can be formed if three solutions of different amino-acids are mixed. E.g. if three different amino acids are met, gly and ser then the possible combinations are met-met, gly-gly, ser-ser, met-gly, gly-met, met-ser, ser-met, gly-ser, and ser-gly. This can also be calculated by using the formula given below,
Formula: n=xy
Where x=number of different amino acids used,
y=number amino acid positions in the peptides.
Hence, n=32
n=9.
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