Bioprocess Engineering online test focuses on “Guidelines for Choosing Host-Vector Systems”.
1. Post-translational modification includes which type of protein modification?
A. Ionic
B. Non-covalent
C. Covalent
D. Metallic
Answer: C
Explanation: Post-translational modification (PTM) refers to the covalent and generally enzymatic modification of proteins following protein biosynthesis. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling.
2. What is the full form of GRAS in the regulatory approval of food products?
A. Generally regarded as sacred
B. Generally recognized as safe
C. Generally recommended as standard
D. Generally recognized standard
Answer: B
Explanation: GRAS stands for in the regulatory approval of food products as “Generally recognized as safe”.
3. E.coli is not a perfect host due to __________
A. Non-proteolytic degradation
B. Proteolytic degradation
C. Retained intercellularly
D. Production at medium levels
Answer: B
Explanation: E. coli is not a perfect host. The major problems result from the fact E. coli does not normally secrete proteins. When proteins are retained intracellularly and produced at high levels, the amount of soluble active protein present is usually limited due to either proteolytic degradation or insolubilization into inclusion bodies.
4. Heat shock method uses ___________
A. Calcium rich environment
B. Magnesium rich environment
C. Potassium rich environment
D. Sodium rich environment
Answer: A
Explanation: In the laboratory, bacterial cells can be made competent and DNA subsequently introduced by a procedure called the heat shock method. Heat shock transformation uses a calcium rich environment provided by calcium chloride to counteract the electrostatic repulsion between the plasmid DNA and bacterial cellular membrane.
5. Inclusion bodies are devoid of proteins.
A. True
B. False
Answer: B
Explanation: Inclusion bodies, sometimes called elementary bodies, are nuclear or cytoplasmic aggregates of stable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins.
6. Resolubilization is generally for the chemical alternations.
A. True
B. False
Answer: B
Explanation: The protein in the inclusion body is misfolded. The misfolded protein has no biological activity and is worthless. If the inclusion bodies are recovered from the culture, the inclusion bodies can be resolubilized and activity restored. When resolubilization is straightforward and recoveries are high, the formation of inclusion bodies can be advantageous, as it simplifies the initial steps of recovery and purification. It is important that during resolubilization the protein be checked by several analytical methods to ensure that no chemical modifications have occurred. Even slight changes in a side group can alter the effectiveness of the product.
7. Endotoxins are intracellular not harmful.
A. True
B. False
Answer: B
Explanation: If the product is retained intracellularly, then the cell must be lysed (broken) during recovery. Lysis usually results in the release of endotoxins (or pyrogens) from E. coli. Endotoxins are lipopolysaccharides (found in the outer membrane) and can result in undesirable side effects (e.g., high fevers) and death. Thus, purification is an important consideration.
8. Pyrogen is __________
A. Antibiotic
B. Non-toxic
C. Drug
D. Fever inducer
Answer: D
Explanation: Pyrogen (fever) is a fever inducing substance.
9. Secretion and excretion are two different terms.
A. True
B. False
Answer: A
Explanation: Secretion is defined here as the translocation of a protein across the inner membrane of E. coli. Excretion is defined as release of the protein into the extracellular compartment.
10. B. subtilis has a number of problems that have hindered its commercial adoption mainly due to:
A. Increased levels of proteins
B. Decreased levels of proteins
C. Increased levels of proteases
D. Decreased levels of proteases
Answer: C
Explanation: A primary concern has been that B. subtilis produces a large amount and variety of proteases. These proteases can degrade the product very rapidly. Mutants with greatly reduced protease activity have become available, but even these mutants may have sufficient amounts of minor proteases to be troublesome. B. subtilis is also much more difficult to manipulate genetically than E. coli because of a limited range of vectors and promoters.
11. What do you mean by glycosylation?
A. Addition of sugar
B. Non-addition of sugar
C. Lysis of sugar moieties
D. Blockage of sugar molecules
Answer: A
Explanation: Glycosylation is a critical function of the biosynthetic-secretory pathway in the endoplasmic reticulum (ER) and Golgi apparatus. Approximately half of all proteins typically expressed in a cell undergo this modification, which entails the covalent addition of sugar moieties to specific amino acids.
12. What is the full form of AOX in Pichia pastoris expression system?
A. Artificial oxidase
B. Acetone oxidase
C. Alcohol oxidase
D. Acetyl oxidase
Answer: C
Explanation: Pichia pastoris has two alcohol oxidase genes, Aox1 and Aox2, which have a strongly inducible promoter. These genes allow Pichia to use methanol as a carbon and energy source. The AOX promoters are induced by methanol and are repressed by e.g. glucose. Usually the gene for the desired protein is introduced under the control of the AOX1 promoter, which means that protein production can be induced by the addition of methanol.
13. Transformed cell lines are immortal.
A. True
B. False
Answer: A
Explanation: Cells that can be propagated indefinitely are called continuous, immortal, or transformed cell lines. Cancer cells are naturally immortal. All cancerous cell lines are transformed, although it is not clear whether all transformed cell lines are cancerous.
14. Baculovirus infects insect cell lines and are also pathogenic to humans.
A. True
B. False
Answer: B
Explanation: The baculovirus that infects insect cells is an ideal vector for genetic engineering, because it is nonpathogenic to humans and has a very strong promoter that encodes for a protein that is not essential for virus production in cell culture. The insertion of a gene under the control of this promoter can lead to high expression levels (40% of the total protein as the target protein).
15. Plant cell cultures are better than animal cultures.
A. True
B. False
Answer: A
Explanation: Plant cell cultures, compared to animal cell cultures, grow to very high cell density, use defined media, and are intrinsically safer.
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