Resting Membrane Potential Overview

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Questions and Answers

What is the primary role of phospholipids in the membrane?

To facilitate enzymatic reactions

To form a lipid bilayer that provides structural integrity (correct)

To transport ions across the membrane

To act as a signal transducer

How does the distribution of cholesterol in the phospholipid bilayer affect the cell?

It increases the permeability of all ions

It aids in the formation of a rigid membrane

It prevents the formation of integral proteins

It regulates fluidity and permeability (correct)

What does the resting membrane potential represent?

The maximum potential reached during an action potential

The membrane potential at which there is no ion movement (correct)

The average potential created by all ions in the cell

The charge difference that promotes ion flow out of the cell

Which of the following statements best describes equilibrium potential?

It occurs when chemical and electrical driving forces are equal and opposite Signup and view all the answers

What does Bernstein’s suggestion about intracellular and extracellular potassium concentrations imply?

Intracellular potassium concentrations exceed extracellular concentrations Signup and view all the answers

What characterizes the equilibrium potential of a cell?

The concentration gradient and electrical force are equal and opposite. Signup and view all the answers

Which role of the Na/K pump is critical in cellular function?

It directly utilizes ATP to pump ions against their gradients. Signup and view all the answers

In secondary active transport, what is utilized to drive the transport of solutes?

The electrochemical gradient of another ion. Signup and view all the answers

How does osmosis contribute to cell dynamics?

It can cause cells to either swell or shrivel depending on solute concentrations. Signup and view all the answers

What is the primary function of aquaporins in the cell membrane?

To facilitate the movement of water molecules. Signup and view all the answers

What is a consequence of deleting the gene for Aquaporin4 in mice?

Sevenfold reduction in water permeability of cell membranes. Signup and view all the answers

How does the capacitative current relate to ionic current in a membrane?

Higher capacitative current corresponds with higher ionic current, maintaining membrane potential. Signup and view all the answers

What distinguishes exchange (antiport) and cotransport (symport) in secondary active transport?

Antiport involves the movement of one solute against its gradient while another is moved down its gradient, whereas symport moves both against their gradients. Signup and view all the answers

Study Notes

Resting Membrane Potential

The cell membrane is a lipid bilayer with embedded proteins, forming a selectively permeable barrier.
Phospholipids are amphiphilic, with hydrophobic tails and hydrophilic heads, spontaneously forming a bilayer in aqueous solutions.
Integral and peripheral proteins facilitate transport and communication across the membrane.
Cholesterol regulates membrane fluidity and permeability.

Bernstein's Model

Intracellular potassium concentration ([K+]in) is greater than extracellular potassium concentration ([K+]out).
Potassium permeability (PK) is significantly higher than the permeability of other ions (Pall).
Resting membrane potential (Vm) is approximately equal to the potassium equilibrium potential (EK).

Electrochemical Equilibrium

Equilibrium potential is the membrane potential at which the chemical and electrical driving forces for an ion are equal and opposite, resulting in no net ion movement.

Maintaining Transmembrane Ion Gradients

The Na+/K+ pump actively transports sodium ions out of the cell and potassium ions into the cell, using ATP.
This pump is electrogenic, contributing a small but significant voltage to the resting membrane potential.
Secondary active transport utilizes the electrochemical gradient of one ion to drive the transport of another. This includes exchange (antiport) and cotransport (symport).
Osmosis is the movement of water across a semi-permeable membrane from an area of high water concentration to low water concentration.
Aquaporins are channels that facilitate water movement across membranes. Their deletion in mice affects water permeability, although other water transport can maintain normal function under normal conditions.

The Membrane as an RC Circuit

The cell membrane acts as both a capacitor and a resistor, influencing how rapidly membrane voltage changes.
Changes in ionic current affect capacitive current and vice-versa, influencing the overall membrane potential.

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Description

Explore the concepts of resting membrane potential, Bernstein's model, and electrochemical equilibrium in this quiz. Understand the roles of cell membrane structure, ion concentrations, and transport mechanisms in maintaining membrane potential. Test your knowledge on how these factors influence cellular functions.