Molecular Biology of the Cell Chapter 012 Test QUIZ BANK Revised Questions & Answers 2023/2024
Half correct answers In eukaryotes, the endoplasmic
... [Show More] reticulum can make up how much the total membrane in a cell?
1. Lipid and protein biosynthesis
2. The intracellular storage of calcium correct answers Give two functions of the ER
Bound ribosomes correct answers Rough ER is studded with what?
Steroid/hormone production correct answers Ribosomes are absent on smooth ER which are specialized for the production of what?
Interconnected correct answers An individual cell contains both smooth and rough ER membranes that are often what?
The specialized function of that cell correct answers The percentage of the ER that is smooth versus rough will vary depending on what?
Co-translationally correct answers The bulk of the proteins targeted are what targeted to the ER explaining the association of ribosomes with ER?
Post-translationally correct answers A small subset of proteins are targeted to the ER what?
Post-translationally correct answers In mammalian cells, proteins less than 70 amino acids in size are transported when?
Co-translationally correct answers In mammalian cells, proteins less than 70 amino acids in size are transported post-translationally; the remaining are transported when?
A: Co-translational translocation
B: Post-translational translocation correct answers Identify A and B
1. Endoplasmic Reticulum
2. Mitochondrial-encoded proteins
3. Chloroplast-encoded proteins correct answers Give some examples of co-translational transport pathways
1. Endoplasmic Reticulum
2. Nuclear-encoded mitochondrial proteins
3. Nuclear-encoded chloroplast proteins
4. Peroxisomes
5. Nucleus correct answers Give some examples of post-translational transport pathways
Isolated ER vesicles correct answers The idea of a targeting signal originated in the 1970's by scientists working on protein transport into what?
Signal hypothesis correct answers What is the idea that proteins destined for the ER had a stretch of amino acids that were recognized by receptors found only in the ER?
Translocation correct answers The ER has a stretch of amino acids that were recognized by recepters found only in the ER. This signal peptide was then removed after what was complete?
Other organelles correct answers The signal hypothesis has expanded to include transport into what?
Cytoplasmic ribosomes correct answers Proteins destined for the ER (or later organelles in the secretory pathway) begin translation on what?
Signal recognition particle (SRP) correct answers When their amino terminal signal sequence emerges from the ribosome it is recognized by a what
ER membrane correct answers SRP binding halts translation and targets the ribosome with its bound mRNA and polypeptide chain to the what?
ER translocation channel correct answers The SRP engages with the what?
ER lumen correct answers SRP is released and ribosome mediated translation continues with the elongating polypeptide entering the what?
The cytosol for another round of protein synthesis correct answers When translation is completed, the ribosome is released from the ER into what? For what reason?
Amino acid sequence conservation correct answers The ER targeting signal has no what?
Charged and nonpolar amino acids correct answers ER targeting signals share a common distribution of what? (2 answers)
The signal sequence binding pocket on SRP correct answers The centrally located hydrophobic stretch of amino acids is recognized by what?
The ER signal peptidase correct answers Following signal sequence binding pocket on SRP is a peptidase cleavage site that is recognized by what?
Both soluble and transmembrane proteins correct answers What two kinds of proteins are targeted to the ER using similarly organized targeting signals?
1. No amino acid sequence conservation
2. 20-30 amino acids in length
3. At the amino terminus of ER targeted proteins
4. Shared pattern of charged and nonpolar amino acids (+ charged N terminus, central hydrophobic domain, polar C-terminus)
5. Peptidase cleavage site follows the signal sequence correct answers Give 5 characteristics of the ER targeting sequence: [Show Less]