Exam 12: Transport Across Cell Membranes

The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell.What type of neurotransmitter is used at these neuromuscular junctions?

Approximately, how many distinct synapses are established on the dendrites and cell body of a motor neuron in the spinal cord?

Which of the following gated ion channels are involved in inhibitory synaptic signaling?

The field of neurobiology is seeing rapid advances in our understanding of neural circuitry in the brain.Part of this work involves the physical mapping of all synapses (a project dubbed the connectome); another critical advance is in the area of optogenetics, which allows scientists to dissect neural circuits that determine specific behaviors in a range of organisms from fruit flies to monkeys. A.Describe the method of optogenetics. B.Optogenetics has great potential for deepening our understanding of behavior, learning, memory, and cognitive development.However, it is not as likely to be used directly for treatment of problems such as depression or anxiety.Why not? Consider the limitations of the method when answering this question.

You have generated antibodies that recognize the extracellular domain of the Ca²⁺-pump.Adding these antibodies to animal cells blocks the active transport of Ca²⁺ from the cytosol into the extracellular environment.What do you expect to observe with respect to intracellular Ca²⁺?

Negatively charged ions are required to balance the net positive charge from metal ions such as K⁺, Na⁺, and Ca²⁺.Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses)?

Describe the two components of an electrochemical gradient.Use your description to suggest which of the following is influenced by a larger electrochemical gradient: (1) Na⁺ moving into the cell; (2) K⁺ moving out of the cell.Explain your reasoning.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant inside a typical mammalian cell?

Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer. A.amino acids or benzene B.Cl⁻ or ethanol C.glycerol or RNA D.H₂O or O₂ E.adenosine or ATP

Which of the following occur WITHOUT coupling transport of the solute to the movement of a second solute?

Which of the following statements about GABA receptors is FALSE?

The movement of glucose into the cell, against its concentration gradient, can be powered by the co-transport of Na⁺ into the cell.Explain the thermodynamic factors governing this transporter.Under what conditions would transport of glucose slow or come to a halt?

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient.This type of transport is called

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules.In the extracellular case, what is the principal anion?

Studies on the squid giant axon were instrumental to our current understanding of how action potentials are generated.You decide to do some experiments on the squid giant axon yourself. A.You remove the cytoplasm in an axon and replace it with an artificial cytoplasm that contains twice the normal concentration of K⁺ by adding KOAc, where OAc⁻ is an anion to which the membrane is impermeable.In this way, you double the internal concentration of K⁺ while maintaining the bulk electrical balance of the cytoplasmic solution.Will this make the resting potential of the membrane more or less negative? B.You add NaCl to the extracellular fluid and effectively double the amount of extracellular Na⁺ ions.How does this affect the action potential? C.You replace half of the NaCl in the extracellular fluid with choline chloride.(Choline is a monovalent cation much larger than Na⁺.Note that the presence of choline will not impede the flow of Na⁺ through its channels.) How will this affect the action potential?

Which of the following best describes the behavior of a gated channel?

If ATP production is blocked in an animal cell, the cell will swell up.Explain this observation.

When the net charge on either side of the plasma membrane is zero, what else is true?