30 Questions
Which of the following is true about the lipid bilayer?
It is impermeable to most water-soluble molecules
What determines the rate of simple diffusion across a protein-free bilayer?
Size and solubility
Which statement about membranes and water permeability is true?
Membranes are a billion times more permeable to water than to small ions
Which of the following is true about transporters and channels?
Transporters transfer solutes at a much slower rate than channels
What are the two means for movement across a selectively permeable membrane?
Diffusion and active transport
Which of the following is true about diffusion?
Diffusion is a passive process
What is the role of membrane transport proteins?
To prevent loss of charged and polar solutes
What are the characteristics of transporters?
They undergo conformational changes
What is the main difference between channels and transporters?
Channels undergo conformational changes while transporters open or close
What is the main function of the lipid bilayer?
To act as a selectively permeable barrier
Which of the following is a major category of gated ion channels?
Voltage-gated channels
What is the driving force for the movement of solutes across the membrane by passive transport?
Electrochemical gradient
What is the measure of polarity and solubility in a nonpolar solvent/water for a molecule?
Partition coefficient
Which of the following processes allows substances to move across membranes directly through the lipid bilayer?
Simple diffusion
What type of transport is characterized by binding to a membrane-spanning protein that changes its shape?
Facilitated transporters
What is the selectivity filter for ion specificity in a potassium channel?
Carbonyl groups
What determines the direction in which each solute will flow across the membrane by passive transport?
Electrochemical gradient
What causes the release of neurotransmitter molecules?
Influx of Ca2+
Which of the following is NOT a process by which substances move across membranes?
Active transport
What type of transport is characterized by opening and closing due to ligand binding?
Ligand-gated channels
Which of the following is true about active transport?
Active transport moves molecules from low to high concentration
What is the purpose of the Na+/K+-ATPase pump?
To establish gradients needed for nerve-muscle impulses
What does the Na+/K+-ATPase pump do to the net charge on each side of the membrane?
Makes the inside of the cell more positive and the outside more negative
How does the Na+/K+-ATPase pump change shape?
Through phosphorylation
What is the purpose of the glucose transporter?
To import glucose into the cell
How does the Na+/glucose cotransporter work?
It moves glucose up its gradient as Na+ flows down its gradient
What is the role of coupled transporters?
To carry >1 type of solute
How many Na+ ions are transported into the cell for every glucose molecule?
2 Na+ ions
What does the movement of 2 moles of Na+ ions into a cell generate?
A glucose concentration that is 30,000 times higher inside than out
What is the purpose of the Na+/H+ exchanger?
To exchange Na+ for H+
Test your knowledge on membrane transport and the role of the lipid bilayer in preventing the loss of charged and polar solutes. Learn about membrane transport proteins and their ability to transfer specific substances across the membrane. Explore the permeability of the lipid bilayer to different molecules.
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