In a neuron, what creates the electrochemical gradient favoring the outflow of K+ when the cell is at rest? a. Na+/K+-ATPase b. voltage-gated K+ channels c. voltage-gated Na+ channels d. ligand-gated Na+/K+ channels

Verified step by step guidance

1. Identify the role of each component listed in the options: Na+/K+-ATPase pumps 3 Na+ ions out and 2 K+ ions into the neuron, using ATP. Voltage-gated K+ channels allow K+ to flow out when open. Voltage-gated Na+ channels allow Na+ to flow in when open. Ligand-gated Na+/K+ channels open in response to a ligand and allow Na+ and K+ to flow according to their gradients.
2. Understand the resting membrane potential: At rest, neurons have a negative internal environment relative to the outside. This is primarily due to the higher concentration of K+ inside and Na+ outside the neuron.
3. Analyze the role of K+ in the resting potential: K+ tends to diffuse out of the neuron due to its concentration gradient, making the inside of the cell more negative.
4. Consider the mechanism that maintains K+ gradient: Na+/K+-ATPase continuously pumps K+ into and Na+ out of the cell, against their concentration gradients, which is crucial for maintaining the gradient that favors K+ outflow.
5. Conclude the correct answer: The electrochemical gradient favoring the outflow of K+ when the cell is at rest is primarily created and maintained by the Na+/K+-ATPase. Therefore, the correct answer is a. Na+/K+-ATPase.

Key Concepts

Electrochemical Gradient

The electrochemical gradient is the difference in charge and concentration of ions across a cell membrane. In neurons, this gradient is crucial for generating action potentials. It is established by the unequal distribution of ions, particularly sodium (Na+) and potassium (K+), which influences the movement of these ions in and out of the cell.

Na+/K+-ATPase

The Na+/K+-ATPase is an enzyme that actively transports sodium out of the cell and potassium into the cell against their concentration gradients. This process is essential for maintaining the resting membrane potential of neurons, as it helps to create and sustain the electrochemical gradient that favors the outflow of K+ when the neuron is at rest.

Resting Membrane Potential

The resting membrane potential is the electrical potential difference across the neuronal membrane when the cell is not actively transmitting signals. Typically around -70 mV, this potential is primarily determined by the permeability of the membrane to K+ ions and the activity of the Na+/K+-ATPase, which together create conditions that favor K+ efflux.