Exam 1 Flashcards
Which properties are characteristic of ion channels?
A. They are usually lipids
B. They exist on one side of the plasma membrane, usually the intracellular side
C. Thy can open and close depending on the presence of any of three types of “gates”
D. They permit movement of ions against concentration gradients
E. They mediate facilitates diffusion
C. Channels are proteins that span the membrane and are opened by ligands, voltage, or mechanical stimuli
Which of the following does not directly or indirectly require an energy source?
A. Primary active transport
B. operation of the Na+/K+ ATPase Pump
C. The mechanism used by cells to produce a calcium ion gradient across the plasma membrane
D. Facilitates transport of glucose across the plasma membrane
E. Secondary Active Transport
D. Facilitated diffusion does not require ATP. Recall that secondary active transport INDIRECTLY requires ATP because ion pumps were required to establish the electrochemical gradient for a particular ion (such as Na+)
Which is (are) true of epithelial cells?
A. They can only move uncharged molecules across their surfaces
B. They may have segregated functions on apical (luminal) and basolateral surfaces
C. They cannot form tight junctions
D. They depend upon the activity of NA+/K+ ATPase pumps for much of their transport
E. Both B and D are correct
E. Segregation of function on different surfaces of the cell, and the ability to secrete chemicals (e.g. from the pancreas) are two of the most important features of epithelial cells
Which is incorrect?
A. Diffusion of a solute through a membrane is considerably quicker than diffusion of the same solute through a water layer of equal thickness
B. A single ion, such as K+, can diffuse through more than one type of channel
C. Lipid soluble solutes diffuse more readily through the phospholipid bilayer of plasma membrane than do water soluble ones
D. The rate of facilitated diffusion of a solute is limited by the number of transporters in the membrane at any given time
E. A common example of cotransport is that of an ion and an organic molecule
A. Diffusion is slowed by the resistance of a membrane
In considering diffusion of ions through an ion channel, which driving force(s) must be considered? A. The ion concentration gradient B. The electrical gradient C. Osmosis D. Facilitated Diffusion E. Both A and B
E. Because ions are charged, both the chemical and the electrical gradients determine their rate and direction of diffusion
Defines the situation when all receptor binding sites are occupied... A. Affinity B. Saturation C. Competition D. Down-Regulation E. Specificity
B - Saturation
Defines the strength of receptor binding... A. Affinity B. Saturation C. Competition D. Down-Regulation E. Specificity
A - Affinity
Reflects the fact that a receptor normally binds only to a single messenger... A. Affinity B. Saturation C. Competition D. Down-Regulation E. Specificity
E - Specificity
Which of the following intracellular or plasma membrane proteins require Ca++ for full activity? A. Calmodulin B. Janus Kinase C. Protein Kinase A D. Guanylyl Cyclase E. All of the above
A. Calmodulin is a calcium binding protein that is inactive in the absence of Ca++
Which is correct?
A. Protein kinase A phophorylates tyrosine residues
B. Protein kinase C is activated by cAMP
C. The subunit of G5 proteins that activates adenylyl cyclase is the beta subunit
D. Lipid-soluble messengers typically act on receptors in the cell cytosol or nucleus
E. The binding site of a typical plasma membrane receptor for its messenger is located on the cytosolic surface of the receptor
D. Lipid soluble messengers cross the plasma membrane and act primarily on cytosolic and nuclear receptors
Inhibition of which enzyme would inhibit the conversion of arachidonic acid to leukotrienes? A. cyclooxygenase B. lipoxygenase C. phospholipase A2 D. adenylyl cyclase E. both B and C
B. lipoxygenase
Which of these synapses does not have acetylcholine as its primary neurotransmitter?
A. Synapse of postganglionic parasympathetic neuron onto a heart cell
B. Synapse of a postganglionic sympathetic neuron onto a smooth muscle cell
C. Synapse of a preganglionic sympathetic neuron onto a postganglionic neuron
D. Synapse of a somatic efferent neuron onto a skeletal muscle cell
E. Synapse of preganglionic sympathetic neuron onto adrenal medullary cells
B. Norepinephrine is the neurotransmitter released by postganglionic neurons onto smooth muscle cells
If a ligand gated channel permeable to both Na+ and K+ was briefly opened at a specific location on the membrane of a typical resting neuron, what would result?
A. local currents on the inside of the membrane would flow away from that region
B. local currents on the outside of the membrane would flow away from that region
C. local currents would travel without decrement all along the cell’s length
D. Fluxes of Na+ and K+ would be equal, so no local currents would flow
A. Because Na+ is farther away from its electrochemical equilibrium than is K+, there would be more Na+ entry than K+ exit, causing local depolarization and local current flow that would decrease with distance from the site of the stimulus
Which is a true statement about the resting membrane potential in a typical neuron?
A. the membrane potential is closer to the Na+ equilibrium potential than to the K+ equilibrium potential
B. The Cl- permeability is higher than for the Na+ and K+
C. The membrane potential is at the equilibrium potential for K+
D. There is no ion movement at the steady resting membrane potential
E. Ion movement by the Na+/K+ ATPase pump is equal and opposite to the leak of ions through Na+ and K+ channels
E. Neither Na+ nor K+ is in equilibrium at the resting membrane potential, but the action of the Na+/K+ ATPase pump prevents the small but steady leak of both ions from dissipating the concentration gradients
Which of the following is an opsonin? A. IL-2 B. C1 protein C. C3b protein D. C-reactive protein E. Membrane attack complex
C. C3b protein
