This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Protein Targeting and Degradation”.
1. Posttranslational modification of many eukaryotic proteins begins in the ____________
a) Endoplasmic reticulum
b) Mitochondria
c) Chloroplasts
d) Nucleus
View Answer
Explanation: Most lysosomal, membrane or secreted proteins have an amino-terminal signal sequence that marks them for translocation into the lumen of the ER.
2. The antibiotic aided in elucidating the steps of protein glycosylation is ____________
a) Streptomycin
b) Tunicamycin
c) Penicillin
d) Crocin
View Answer
Explanation: It acts by interfering with one or more steps in this process.
3. The coated pits are coated on their cytosolic side with a lattice of ____________
a) Clathrin
b) Lipoprotein
c) Glycoprotein
d) Transferrin
View Answer
Explanation: Clathrin is coated on the cytosolic side of the coated pits.
4. How many amino acid residues are there in ubiquitin?
a) 72
b) 73
c) 75
d) 76
View Answer
Explanation: One of the most highly conserved proteins is known as ubiquitin (76 amino acid residues).
5. What are the two subassemblies of 26S proteasome?
a) 20S core particle and 19S regulatory particle
b) 20S regulatory particle and 19S core particle
c) 18S core particle and 19S regulatory particle
d) 20S core particle and 18S regulatory particle
View Answer
Explanation: The two subassemblies are 20S core particle and 19S regulatory particle.
6. Proteins tagged with mannose 6-phosphate are transported to ____________
a) Golgi complex
b) Mitochondria
c) Lysosome
d) Nucleus
View Answer
Explanation: The presence of one or more mannose 6-phosphate residues in its N-linked oligosaccharide is the structural signal that targets the protein to lysosomes.
7. Signal sequences are ____________
a) Short peptide sequences attached to a protein that initiates its degradation by digestive enzymes
b) Short peptide sequences to transport a protein to the nucleus
c) Glycoproteins that serve as an address for transporting newly synthesized protein to the correct location
d) Short peptide sequences that serve as an address for transporting newly synthesized proteins to the correct location
View Answer
Explanation: The signal sequence directs a protein to its appropriate location in the cell.
8. Which is the correct order of transport of protein in a secretory pathway?
a) Protein synthesized in the cytoplasm-SER lumen-RER lumen-cis Golgi-median Golgi-trans Golgi-vesicles-fusion of vesicles with plasma membrane-exocytosis
b) Protein synthesized in the cytoplasm-RER lumen-cis Golgi-median Golgi-trans Golgi-vesicles-fusion of vesicles with plasma membrane-exocytosis
c) Protein synthesized in the cytoplasm- vesicles -SER lumen-RER lumen-cis Golgi-median Golgi-trans Golgi-fusion of vesicles with plasma membrane-exocytosis
d) Protein synthesized in the cytoplasm- RER lumen-trans Golgi -median Golgi-cis Golgi -vesicles-fusion of vesicles with plasma membrane-exocytosis
View Answer
Explanation: Protein synthesized in the cytoplasm-RER lumen-cis Golgi-median Golgi-trans Golgi-vesicles-fusion of vesicles with plasma membrane-exocytosis.
9. Nuclear localization signal is rich in ____________
a) Tryptophan and histidine
b) Serine and threonine
c) Glutamine and asparagine
d) Lysine and arginine
View Answer
Explanation: Nuclear localization signal is rich in lysine and arginine.
10. Secretory proteins are synthesized by ____________
a) Ribosomes on the nuclear membrane
b) Ribosomes on endoplasmic reticulum
c) Free ribosomes
d) None of the mentioned
View Answer
Explanation: Ribosomes on endoplasmic reticulum synthesize secretory proteins.
Sanfoundry Global Education & Learning Series – Biochemistry.
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