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
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
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
Explanation: Clathrin is coated on the cytosolic side of the coated pits.
4. How many amino acid residues are there in ubiquitin?
Explanation: One of the most highly conserved proteins is known as ubiquitin (76 amino acid residues).
5. The two subassemblies of 26S proteasome are
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
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
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 serves as an address for transporting newly synthesized proteins to the correct location
Explanation: The signal sequence directs a protein to its appropriate location in the cell.
8. The correct order of transport of protein in a secretory pathway is
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
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
Explanation: Nuclear localization signal is rich in lysine and arginine.
10. Secretory proteins are synthesized by
a) Ribosomes on nuclear membrane
b) Ribosomes on endoplasmic reticulum
c) Free ribosomes
d) None of the mentioned
Explanation: Ribosomes on endoplasmic reticulum synthesize secretory proteins.
Sanfoundry Global Education & Learning Series – Biochemistry.
To practice all areas of Biochemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.