Molecular Biology Chapter 15 Practice Questions
Which organelle contains enzymes used in a variety of oxidative reactions that break down lipids and destroy toxic
A peroxisome
What protein can assemble into a basket-like network that gives budding vesicles their shape?
Clathrin
Which of the following is true?
A common pool of ribosomes is used to synthesize both the proteins that stay in the cytosol and those that are destined for the ER.
Which organelle is essentially a small sac of digestive enzymes that functions in degrading worn-out organelles, as well as macromolecules
A lysosome
Which organelle sorts ingested molecules and recycles some of them back to the plasma membrane?
An endosome
Which mechanism is used for degrading obsolete parts of a cell, such as a defective mitochondrion?
Autophagy
The interiors of the ER, Golgi apparatus, endosomes, and lysosomes communicate with each other in which of the following ways?
By small vesicles that bud off of one organelle and fuse with another
How do proteins travel from one cisterna to the next in the Golgi apparatus?
By transport vesicles that bud off from one cisterna and fuse with the next cisterna
Which type of protein binds to improperly folded or improperly assembled proteins in the ER, holding them there until proper folding occurs?
Chaperone proteins
The movement of materials from the plasma membrane, through endosomes, and then to lysosomes describes which type of pathway?
Endocytic pathway
Which cellular compartment acts as the main sorting station for extracellular cargo molecules taken up by endocytosis?
Endosomes
Eukaryotic cells continually ingest bits of their plasma membrane, along with small amounts of extracellular fluid. The lost pieces of membrane are replaced by the process of:
Exotycosis
Which of the following organelles is not surrounded by a double membrane?
Golgi apparatus
Which of the following is NOT true of receptor-mediated endocytosis?
In receptor-mediated endocytosis, internalized vesicles fuse with lysosomes, which then mature into endosomes.
Most mitochondrial and chloroplast proteins are made in which compartment of the cell?
In the cytosol
In the process of translocating a polypeptide across the membrane of the endoplasmic reticulum, a stop transfer sequence halts the process. What eventually becomes of the stop transfer sequence?
It forms an /alpha-helical membrane-spanning segment of the protein.
Which of the following is true of lysosomes?
Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes
Which proteins bind to nuclear localization signals on newly synthesized proteins?
Nuclear import receptors
Cells ingest large particles by:
Phagocytosis
In the unfolded protein response, the accumulation of misfolded proteins in the ER serves as a signal for the cell to do which of the following?
Produce more ER
Mitochondria and peroxisomes do NOT have what in common?
Proteins need to unfold to enter them
Which proteins play a central role in the fusion of a vesicle with a target membrane?
SNARE proteins
Which organelle receives proteins and lipids from the endoplasmic reticulum, modifies them, and then dispatches them to other destinations in the cell?
The Golgi apparatus
Proteins that lack a sorting signal remain as permanent residents of which part of a eucaryotic cell?
The cytosol
Many proteins are glycosylated in:
The endoplasmic reticulum
Proteins in the cytosol that are destined for other organelles must first enter the:
The endoplasmic reticulum
The outer membrane of the nucleus is continuous with the membrane of which other organelle?
The endoplasmic reticulum
Which organelle is the major site of new membrane synthesis in a cell?
The endoplasmic reticulum
Proteins have to unfold during their transport across the membranes of all but one of the following organelles. Which one?
The nucleus
If a signal sequence is removed from an ER protein:
The protein remains in the cytosol
Which of the following statements is NOT true of mitochondrial proteins that are synthesized in the cytosol?
The proteins are transported across the mitochondrial membranes while being synthesized
Proteins entering the cisGolgi network can do which of the following?
They can either move onward through the Golgi stack or be returned to the ER.
Which of the following is NOT a role for the oligosaccharides on glycosylated proteins?
They can provide a source of energy for the cell.
What distinguishes proteins destined for regulated secretion?
They have special surface properties that cause them to form aggregates that are packaged into secretory vesicles
The constitutive exocytosis pathway of the Golgi apparatus operates continually in all eucaryotic cells
True
Vesicle budding is driven by the assembly of a protein coat.
True
Which molecule is displaced when a vesicle and its target membrane fuse?
Water
The low pH inside endosomes:
causes internalized receptors to release their cargo.
The ER signal sequence on a growing polypeptide chain is recognized by a signal recognition particle (SRP) in the cytosol. This interaction:
guides the ribosome and its polypeptide to the ER membrane.
Phagocytic cells include:
macrophages and neutrophils.
