Cell phys 11,12,15 quizzes
Shown is a diagram of a nerve cell. Which line indicates the location of the dendrites?
2
Approximately what percentage of the volume of a typical eukaryotic cell is comprised of cytosol?
50%
Which of the following represents a symport transporter protein?
A
How does an action potential spread along the cell membrane?
A change in membrane potential triggers the opening of nearby voltage-gated sodium channels in a one-way direction.
A sodium-potassium antiport maintains the extracellular concentration of sodium at levels that are about 20-30 times higher than inside the cells. What directly supplies the energy for maintaining this gradient?
ATP hydrolysis drives the function of the pump.
Which of the following accurately describes a step in GTP-driven nuclear transport?
Binding of Ran-GTP to the receptor releases the cargo protein.
Which of the following ions has a low cytosolic concentration so that a flood of this ion into the cell can be used as a signal for cell processes like fertilization?
Ca2+
How do clathrin-coated vesicles select their cargo molecules?
Cargo receptors bind specifically to cargo proteins and to clathrin.
How are misfolded proteins and incompletely assembled proteins retained in the ER?
Chaperone proteins bind them and prevent their entry into vesicles.
Which of the following is a difference between exocytic and endocytic pathways?
Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins.
How is the protein shown in the diagram associated with the plasma membrane?
It is associated with one layer of the lipid bilayer.
Which ion is generally maintained at a high concentration inside the cell and a low concentration outside the cell?
K+
Which of the following is NOT used as a source of energy by a transmembrane pump to actively transport a solute?
K+
________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass.
Lipids, proteins
In a fluorescence recovery after photobleaching (FRAP) experiment, a fluorescently tagged membrane protein, A, shows very little recovery of fluorescence ten minutes after photobleaching, while membrane protein B shows a rapid increase in fluorescence after bleaching, recovering nearly 80% of its original fluorescent signal by ten minutes. Based on this information, which of the following statements can be made?
Protein B is diffusing in a more fluid membrane.
What is one of the main differences in the behavior of the proteins in a vesicle destined for constitutive secretion, and the proteins in the vesicle destined for regulated secretion?
Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle.
In a famous experiment, mouse cells and human cells were fused into hybrid cells and the membrane proteins of human origin and mouse origin were specifically tagged and examined. After cell fusion and incubation, what was observed by investigators?
The mouse and human proteins mixed evenly throughout the membrane of the hybrid cell.
What is the role of K+-gated ion channels in an action potential?
They help reverse the action potential by repolarizing the cell.
Which of the following is a difference between transporters and channels?
Transporters can facilitate both active or passive transport of solutes; channels facilitate only passive transport
How is an electrical signal converted to a chemical signal at a nerve terminal?
Voltage-gated Ca2+ channels are activated and the influx of Ca2+ triggers the release of neurotransmitters.
How are voltage-gated ion channels opened by voltage sensors?
When membrane potential changes sufficiently, the electrical force causes voltage sensor domains to change conformation.
A single-pass transmembrane protein destined for one of the organelles in the endomembrane system would be marked by what type of signal sequence?
a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence
Which of the following would be able to cross a protein-free lipid bilayer most rapidly?
a steroid hormone (nonpolar, large)
Detergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane.
amphipathic
If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer?
because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer
Which of the following is a common transmembrane protein structure that can traverse the membrane to form a pore or channel by alternating hydrophobic and hydrophilic amino acids?
beta barrel
Which factors determine the force driving the passive transport of charged solutes across the membrane?
electrochemical gradient
What would the final destination be for a protein bearing both an ER sorting signal and a nuclear localization signal?
endoplasmic reticulum
Where are new phospholipids made?
endoplasmic reticulum
Which type of movement is the least common for lipids in a bilayer?
flip-flop
Which of the following is a covalent modification that occurs mainly in the ER?
formation of disulfide bonds
What is responsible for moving glucose from the gut lumen into intestinal epithelial cells?
glucose-sodium symport
Which of the following organelles is surrounded by a single membrane?
golgi apparatus
Lysosomes contain ____________ enzymes that can break down diverse macromolecules, cell parts, and microorganisms.
hydrolytic
Phospholipids assemble into in a membrane using
hydrophobic forces
Proteins encoded by nuclear genes and destined for the mitochondrial matrix are
in possession of a signal sequence for targeting to the mitochondria.
What is the conformation of the voltage-gated Na+ channel that keeps the action potential from traveling backward along the axonal membrane?
inactivated
Nuclear pores restrict larger molecules from traversing the membrane due to their
interwoven meshwork of protein fibrils.
An extracellular molecule binds to a channel and triggers it to move more often to the open conformation than the closed conformation, as shown in the figure. This is referred to as a ___________ channel.
ligand-gated
A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)?
long, saturated fatty acid tails
A less permeable membrane is likely to have
more cholesterol
Which of the following is a cell type in humans that uses voltage-gated ion channels?
muscle cells
Which of these macromolecules is NOT commonly found in the plasma membrane?
nucleic acids
Fully folded proteins can be transported into which of the following organelles?
nucleus
Which of the following organelles is NOT a part of the endomembrane system?
nucleus
Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins.
peripheral membrane
Which of the following compartments receives proteins directly from cytosol?
peroxisomes
Which of the endocytic pathways involves the ingestion of large particles or microorganisms and is performed mainly by specialized cells?
phagocytosis
What kind of lipid molecule is represented in this figure?
phospholipid
Which of the following pathways helps selectively concentrate substances to be ingested by their binding to proteins on the cell surface?
receptor-mediated endocytosis
Which of the following is NOT a way that cells restrict the lateral movement of membrane proteins?
reducing the temperature of the membrane
A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane?
scramblase
Ion channels contain a selectivity filter that
selects for ions based on size and charge due to the width of the channel and charge of amino acids lining the channel.
Cells, compared with the extracellular fluid are
slightly negatively charged.
Which of the following organelles is the site of steroid hormone synthesis in endocrine cells?
smooth ER
If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane?
the cytosolic face of the bilayer
What is the molecular target of the antidepressant Prozac?
the symport that drives reuptake of serotonin
Why do cells regulate their membrane fluidity?
to allow membrane proteins to diffuse to where they are needed for their function
Plasma membrane proteins that move ions in and out of cells using active transport are called
transporters
In which process do Rab proteins function?
vesicle tethering
