Cell Biology: Resting Membrane Potential

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Questions and Answers

What is the typical range of the resting membrane potential in animal cells?

-70 to -110 mV

-20 to -90 mV (correct)

0 to 20 mV

-10 to 10 mV

Which ion channels are characterized by high selectivity for specific ions?

Carrier proteins

Gap junctions

Aquaporins

Ion channels (correct)

How is the membrane potential expressed?

As the potential inside the cell relative to the extracellular solution (correct)

As the potential difference across the nuclear membrane

As the average potential of all ions inside the cell

As the potential outside the cell relative to the inside

What mechanism allows ions to permeate through the cell membrane?

Facilitated diffusion via channel proteins Signup and view all the answers

Which of the following describes how ion channels can change their state?

By a conformational change in the protein molecule Signup and view all the answers

What is the role of the resting membrane potential in cells?

It forms the basis for cellular signaling. Signup and view all the answers

What is meant by the term 'gating' in the context of ion channels?

The capability of the channel to open or close Signup and view all the answers

What does the membrane potential provide the basis for in the nervous system?

Signaling Signup and view all the answers

What is the primary ionic composition inside a typical mammalian cell at rest?

High K+ and low Na+ concentrations Signup and view all the answers

What causes the inside of the cell to become negatively charged during resting potential?

The efflux of K+ ions while anions remain Signup and view all the answers

Which ion is primarily responsible for establishing the resting membrane potential?

K+ Signup and view all the answers

What is the concentration of Na+ ions outside a typical mammalian cell?

145 mM Signup and view all the answers

Which component of the cell contributes to the negative charge inside the cell?

Organic anions (A-) Signup and view all the answers

What does the selective permeability of the membrane primarily allow at rest?

Permeability to K+ Signup and view all the answers

How does the concentration gradient affect potassium ions during resting potential?

K+ diffuses out of the cell down its concentration gradient Signup and view all the answers

What is the role of large intracellular proteins in the resting potential?

They contribute to the negative charge inside the cell Signup and view all the answers

What is primarily responsible for the resting membrane potential of nerves and muscles?

K+ concentrations inside the cell Signup and view all the answers

What does the Nernst equation allow you to calculate?

The membrane potential where K+ is in equilibrium Signup and view all the answers

What defines the electrical disequilibrium across the cell membrane?

More positive charges outside and more negative charges inside the cell Signup and view all the answers

At what membrane potential does net diffusion of K+ ions across the membrane stop?

When electrical force equals chemical force for K+ Signup and view all the answers

What indicates the direction of the electrochemical gradient for K+ ions?

Electrical forces favor K+ entering the cell Signup and view all the answers

What is the range of resting membrane potential values for nerves and muscles?

-40 mV to -90 mV Signup and view all the answers

Which type of ions are primarily involved in establishing a membrane potential?

Potassium ions (K+) Signup and view all the answers

What is the membrane potential symbol for the K+ equilibrium potential?

EK Signup and view all the answers

What does the Nernst equation primarily calculate?

The equilibrium potential for an ion Signup and view all the answers

In the Nernst equation for potassium ions (K+), what does the valency (Z) equal?

+1 Signup and view all the answers

At what temperature is it common to calculate the Nernst equation constants using log10?

37°C Signup and view all the answers

What is the equilibrium potential for sodium ions (Na+) given an outside concentration of 142 m Eq/L and an inside concentration of 14 m Eq/L?

+55 mV Signup and view all the answers

What is a key characteristic of the resting membrane potential in cardiac muscle and nerve cells?

It is quite close to EK Signup and view all the answers

How do changes in membrane potential affect cellular functions?

They underlie many forms of signaling between and within cells Signup and view all the answers

When sodium ions (Na+) leave a cell, what typically happens to the inside charge of the cell?

It becomes less negative Signup and view all the answers

What is the equilibrium potential for K+ ions when the outside concentration is 4.0 m Eq/L and the inside concentration is 140 m Eq/L?

-94 mV Signup and view all the answers

Study Notes

Membranes and Receptors Module, Session 3, Lecture 3.1: The Resting Cell Membrane

The module covers membranes and receptors.
The lecture focuses on the resting cell membrane and its potential.
Lecturer: Dr. Safa Amir

Objectives of the Lecture

Understand the membrane potential in cells.
Outline how membrane potentials are set up.
Explain how membrane potentials change due to cellular signaling.
Understand ionic equilibrium potential, and how to calculate its value.

The Membrane Potential (Objective 1)

All cells have a voltage difference across their plasma membrane.
This potential is critical for signaling, especially in the nervous system.
The resting membrane potential is the voltage difference across the membrane of a living cell.

Resting Potentials (Objective 1)

Membrane potentials are always expressed as the inside of the cell relative to the extracellular solution.
The measurable unit is millivolts (mV).
Animal cells typically show negative resting membrane potentials, varying from -20 mV to -90 mV.

Selective Permeability (Objective 2)

Membrane potentials arise from selective ion permeability.
The cell membrane is selectively permeable because of ion channels.
Ion channels are membrane-spanning proteins that allow ions to permeate.
Ion channels demonstrate selectivity (allows only certain ions to pass).
Ion channels can be opened/closed by conformational changes in the protein molecule.
These channels facilitate high rates of ion flow along the electrochemical gradient.

Setting up the Resting Potential (Objective 2)

Ion concentrations determine the resting potential.
- Intracellular:
  - Na+ : 10 mM
  - K+ : 160 mM
  - Cl- : 3 mM
  - A- : 167 mM
- Extracellular:
  - Na+ : 145 mM
  - K+ : 4.5 mM
  - Cl- : 114 mM
  - A- : 40 mM
A- represents anions other than Cl-, including phosphate, acids, and proteins,

Ion Distribution (Objective 2)

Anions (-): mainly large intracellular proteins and chloride ions.
Cations (+): primarily sodium (Na+) and potassium (K+).

Resting Membrane Potential (Objective 2)

At rest, the membrane is permeable to potassium (K+)
K+ moves out of the cell down its concentration gradient.
Anions (A-) are trapped inside the cell
This creates a negative charge inside the cell.
Electrical and diffusional forces equilibrate.
- No net movement of K+.

Nernst Potential (Objective 3)

The membrane potential at which the net diffusion of ions stops (due to concentration gradient).

The Nernst Equation (Objective 3)

Used to calculate the equilibrium potential (EK) for an ion.
Relates potential difference to the concentration gradient of an ion.
Key components:
- The membrane potential, V
- The gas constant, R
- Temperature, T
- Valence (charge), Z
- Faraday's number, F
- Ion concentrations inside and outside the cell

Equilibrium Potential (Objective 3)

For an ion, the membrane potential at which there is no net movement of the ion
It depends on ion concentrations on either side of the membrane and the valence of the ion.
Nernst equation is used to calculate the equilibrium potential for any ion.
Specific calculation of K+ and Na+ potentials are provided.

Changing Membrane Potentials (Objective Summary)

Changes in membrane potential underlie many forms of cell signaling. Examples include: action potentials in nerve/muscle cells, muscle contraction, neurotransmitter secretion, sensory information transduction and postsynaptic actions.

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Description

Test your knowledge on the resting membrane potential in animal cells with this quiz. Explore concepts such as ion channels, membrane potential expressions, and their roles in cellular functions, particularly in the nervous system. Enhance your understanding of how these mechanisms contribute to cell signaling.