Small-Molecule Transport and Electrical Properties of Membranes

What is the primary factor, besides molecular size, that determines the rate at which a molecule will diffuse across a protein-free lipid bilayer?

What are the two major classes of membrane transport proteins that enable specific hydrophilic solutes to cross cell membranes?

How much faster is transport through a typical ion channel compared to the rate of a typical transporter?

In the context of membrane transport, what two forces combine to form the electrochemical gradient for a charged solute?

What is the term for a transporter that moves two different solutes across the membrane in the same direction?

What type of pump is the Na+-K+ pump in animal cells?

According to the mechanism of the sarcoplasmic reticulum Ca2+ pump, what event is triggered by the binding of two Ca2+ ions from the cytosol?

How many Na+ and K+ ions are transported, and in which directions, for every molecule of ATP hydrolyzed by the Na+-K+ pump?

What is the primary function of the multidrug resistance (MDR) protein, a type of ABC transporter?

The CFTR protein, associated with cystic fibrosis, is an unusual member of the ABC transporter family because its ATP binding and hydrolysis primarily serve to do what?

What structural feature of aquaporins allows them to be highly permeable to water while completely blocking the passage of ions like H+?

What is the narrowest part of an ion channel, which is primarily responsible for determining which ions can pass through?

What is the primary role of K+ leak channels in an animal cell's plasma membrane?

According to the Nernst equation, what would the equilibrium potential be for a univalent cation at 37 degrees Celsius if its concentration outside the cell is 10 times greater than inside the cell?

How does a bacterial K+ channel achieve selectivity for K+ ions over the smaller Na+ ions?

What is the direct trigger for the generation of an action potential in electrically excitable cells like neurons?

What is the primary event that causes the rapid repolarization (the falling phase) of the membrane potential during an action potential?

What is the function of the myelin sheath that insulates the axons of many vertebrate neurons?

What does patch-clamp recording of a single voltage-gated Na+ channel reveal about its opening and closing behavior?

At a chemical synapse, what event is directly triggered by the influx of Ca2+ into the presynaptic nerve terminal?

How do excitatory neurotransmitters typically cause depolarization of the postsynaptic membrane?

What distinguishes ionotropic receptors from metabotropic receptors at a chemical synapse?

The acetylcholine receptor at the vertebrate neuromuscular junction is composed of how many transmembrane polypeptide subunits?

What is the key condition, besides the binding of glutamate, that must be met for an NMDA-receptor channel to open?

The influx of which ion through NMDA receptors is critical for triggering long-term potentiation (LTP)?

What kind of protein is channelrhodopsin, which is used in the field of optogenetics?

In a typical mammalian cell, what is the approximate ratio of the extracellular Na+ concentration to the cytoplasmic Na+ concentration?

The resting membrane potential of an animal cell typically ranges between what values?

In the mechanism of a voltage-gated Na+ channel, what structural component acts as the primary voltage sensor?

What is the term for the brief period after an action potential during which a neuron cannot fire another one?

How do inhibitory neurotransmitters like GABA and glycine typically suppress neuronal firing?

What percentage of a typical animal cell's metabolic energy is devoted to fueling the Na+-K+ pump?

In transcellular transport of glucose across an intestinal epithelial cell, what type of transporter is responsible for moving glucose out of the cell into the extracellular fluid on the basolateral side?

What is the common structural motif from which many transporters, including the bacterial Na+/leucine symporter, are built?

What is the role of the tight junction in the transcellular transport of solutes across an epithelial sheet?

The bacterial MscS channel, a mechanosensitive channel, is composed of how many identical subunits?

In addition to neurons, which of the following cell types are also described as electrically excitable?

What is saltatory conduction in a myelinated axon?

The drug curare, used as a muscle relaxant, acts by blocking which specific receptors?

In the sequential activation of channels for neuromuscular transmission, which event immediately follows the depolarization of the muscle cell plasma membrane by acetylcholine?

A neuron's ability to encode the intensity of a stimulus into the frequency of action potentials is primarily performed at which specialized region?

What is the function of the Ca2+-activated K+ channels in the initial segment of a neuron?

The human brain is estimated to contain approximately how many neurons?

In the context of synaptic plasticity, long-term depression (LTD) is associated with what cellular event?

A concentration difference of 0.1 M of tryptophan would cause a flow of how many molecules per second through 1 micrometer squared of a synthetic lipid bilayer?

What is the defining characteristic of a P-type ATPase pump?

Piezo channels, which are mechanosensitive, are composed of how many identical subunits?

What is the approximate speed at which an action potential can travel along a large, myelinated neuron?

What is the primary structural difference between transporters that mediate active transport and those that mediate passive transport?

The transport of which of the following is an example of primary active transport?