Chapter 15 Intracellular Compartments and Transport
An individual transport vesicle
will fuse with only one type of membrane.
A transmembrane protein that is integrated into the endoplasmic reticulum, with only ONE transmembrane domain will have:
A cleavable signal sequence AND a stop-transfer sequence
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 and particles taken into the cell by endocytosis?
A lysosome
Which organelle contains enzymes used in a variety of oxidative reactions that break down lipids and destroy toxic molecules?
A peroxisome
After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode?
All except mitochondrial membrane proteins
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
What protein can assemble into a basket-like network that gives budding vesicles their shape?
Clathrin
If a protein has both a nuclear localization sequence and an ER signal sequence, which will take precedence? (Where will the protein end up in the cell?)
ER
Name the membrane-bound compartment where new membrane synthesis takes place.
ER endoplasmic reticulum
The movement of materials from the plasma membrane, through endosomes, and then to lysosomes describes which type of pathway?
Endocytic pathway
What path does a secreted protein follow on its way out of the cell?
Endoplasmic reticulum to Golgi apparatus to secretory vesicles, to the outside of the cell.
Which cellular compartment acts as the main sorting station for extracellular cargo molecules taken up by endocytosis?
Endosomes
The inner membrane of mitochondria will be most similar to eukaryotic membranes.
False
Name the membrane-bound compartment where modification of secreted proteins takes place.
Golgi Apparatus rough ER Golgi rough endoplasmic reticulum
Which of the following organelles is not surrounded by a double membrane? A. Mitochondrion B. Chloroplast C. Golgi apparatus D. Nucleus
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.
What is the role of the nuclear localization sequence in a nuclear protein?
It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
Which of the following is true of lysosomes?
Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes.
Which of the following statements about import of proteins into mitochondria are TRUE?
Mitochondrial proteins are translocated across the inner and outer membranes simultaneously
Which proteins bind to nuclear localization signals on newly synthesized proteins?
Nuclear import receptors
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.
Pancreatic cells that produce and release digestive enzymes engage in what type of secretion?
Regulated secretion . In constitutive secretion, vesicles fuse with the membrane as soon as they pinch off the Golgi - you don't want that, if the vesicle contains digestive enzymes. Cells should only release digestive enzymes when they are needed, therefore this is an example of regulated secretion.
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
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
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.
(T/F) Vesicle budding is driven by the assembly of a protein coat.
True
The constitutive exocytosis pathway of the Golgi apparatus operates continually in all eucaryotic cells.
True
Which molecule is displaced when a vesicle and its target membrane fuse?
Water
Proteins destined to enter the endoplasmic reticulum
begin to cross the membrane while still being synthesized.
The low pH inside endosomes:
causes internalized receptors to release their cargo.
Name the membrane-bound compartment where photosynthesis takes place.
chloroplast
Having a cytoplasmic membrane system is characteristic of what types of cells?
eukaryotic cells
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:
exocytosis
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.
Name the membrane-bound compartment where degradation of worn out organelles takes place.
lysosome
Phagocytic cells include:
macrophages and neutrophils.
Name the membrane-bound compartment where oxidative phosphorylation takes place.
mitochondria
Name the membrane-bound compartment where transcription takes place
nucleus
Name the membrane-bound compartment where breakdown of lipids and toxic molecules take place.
peroxisomes
A type of endocytosis is __________________, which is used to take up large vesicles that can contain microorganisms and cellular debris.
phagocytosis
Cells ingest large particles by:
phagocytosis
One type of endocytosis is __________________, which involves utilizing __________________ proteins to form small vesicles containing fluids and molecules.
pinocytosis, clathrin
Proteins that lack a sorting signal remain as permanent residents of which part of a eukaryotic 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.
If a signal sequence is removed from an ER protein:
the protein remains in the cytosol.
If you compared the proteins that are in a cis Golgi compartment to those that are in a trans Golgi compartment, you would find that:
the proteins in the two compartments have different oligosaccharides attached.
Which of the following are NOT associated with coated pits?
trans Golgi network
