Cell Biology: Ion Channels and Membrane Potential

Questions and Answers

What determines the resting membrane potential?

Chloride ion activity

Potassium channel selectivity (correct)

Calcium ion concentration

Sodium channel permeability

Which mechanism leads ions to diffuse through gated channels when they are open?

Magnetic gradients

Mechanical vibrations

Thermal energy levels

Chemical concentration gradients (correct)

What role do pore loop areas play in potassium channels?

They aid in energy production

They stabilize membrane potential

They are important for selectivity filter (correct)

They facilitate ion synthesis

What happens to the resting membrane potential in response to increased extracellular potassium concentration?

Depolarization occurs Signup and view all the answers

What discovery is associated with the Shaker potassium channel?

It is involved in inherited neurological disorders Signup and view all the answers

How many subunits do potassium channels consist of?

Four Signup and view all the answers

Which scientist was awarded the Nobel Prize for research related to potassium channels?

David MacKinnon Signup and view all the answers

What is the main factor influencing the resting membrane potential's sensitivity to external changes?

Potassium ion concentration Signup and view all the answers

What is the primary reason for the resting membrane potential being negative inside the cell?

Potassium ions diffuse out of the cell more than sodium ions diffuse in. Signup and view all the answers

How does the sodium-potassium pump contribute to the stability of the resting membrane potential?

By maintaining an unequal concentration of sodium and potassium across the membrane. Signup and view all the answers

Which of the following ions has the highest permeability in the resting membrane potential?

Potassium (K+) Signup and view all the answers

What aspect most directly determines the resting membrane potential?

Ion concentration differences inside and outside the cell. Signup and view all the answers

Why are neuron membranes described as being permeable to more than one type of ion?

Because different ion channels exist that allow various ions to pass through. Signup and view all the answers

What are channel proteins primarily responsible for in the neuronal membrane?

Ion transport, selectivity, and gating Signup and view all the answers

Which level of protein structure refers to the coiling of the amino acid sequence into a helix or folding into a sheet?

Secondary structure Signup and view all the answers

What process allows dissolved ions to distribute evenly across the neuronal membrane?

Diffusion down a concentration gradient Signup and view all the answers

What are amino acids joined together by to form polypeptides?

Peptide bonds Signup and view all the answers

Which type of protein is specifically mentioned as being responsible for energy use from ATP breakdown in neuronal signaling?

Ion pumps Signup and view all the answers

What is defined as the force exerted on a charged particle in the neuronal membrane?

Electrical potential (voltage) Signup and view all the answers

Which disorder is linked to issues with channel proteins?

Epilepsy Signup and view all the answers

How do polar and nonpolar R groups influence channel proteins in the neuronal membrane?

They enable the proteins to be fitted inside the membrane. Signup and view all the answers

What is the main function of enzymes as proteins in the neuronal membrane?

To facilitate chemical reactions Signup and view all the answers

Which term describes how easily electrical charges can move across a membrane?

Conductance Signup and view all the answers

What is defined as the measure of potential energy generated by separated charge?

Voltage Signup and view all the answers

Which equation represents Ohm’s law?

I = gV Signup and view all the answers

What happens to current if resistance increases while voltage remains constant?

Current decreases Signup and view all the answers

What characterizes a conductor as opposed to an insulator?

Low electrical resistance Signup and view all the answers

What is required to maintain opposite charges separated across a membrane?

Energy Signup and view all the answers

At equilibrium potential (Eion), what occurs with ion movement?

No net movement of ions occurs Signup and view all the answers

What will occur if K+ channels are inserted into a phospholipid bilayer?

K+ will flow down the concentration gradient Signup and view all the answers

What condition is necessary for greater current flow according to Ohm's Law?

Higher voltage Signup and view all the answers

Which of the following represents resistance?

$1/g$ Signup and view all the answers

When there is no net current flow between two points, what do those points have?

Same electrical potential Signup and view all the answers

What is primarily responsible for the large changes in membrane potential being influenced by tiny amounts of ion concentration changes?

The net difference in electrical charges Signup and view all the answers

Which equation allows for the calculation of the equilibrium potential for an ion?

Nernst equation Signup and view all the answers

Which ion is more concentrated inside the neuronal cell at rest?

K+ Signup and view all the answers

How much ATP can be utilized by the sodium-potassium pump in the brain?

70% Signup and view all the answers

What is the primary function of the calcium pump in neuronal cells?

Transport Ca2+ out of cytosol Signup and view all the answers

What factor does the Nernst equation NOT take into account when calculating the equilibrium potential?

Membrane thickness Signup and view all the answers

What determines the rate of movement of ions across the membrane?

The membrane potential and ion equilibrium potential Signup and view all the answers

What does the sodium-potassium pump achieve in terms of ion transport?

3 sodium ions out, 2 potassium ions in Signup and view all the answers

Study Notes

Neuronal Membrane Components

Proteins are critical in neuronal membranes, composed of amino acids that construct enzymes, cytoskeletal elements, and receptors.
Membrane proteins span the phospholipid bilayer, essential for regulating resting and action potentials.

Protein Structure

Proteins consist of amino acids bound by peptide bonds to form polypeptides.
Four levels of protein structure:
- Primary: sequence of amino acids
- Secondary: coiling into a helix or folding into sheets
- Tertiary: 3D shape from further folding
- Quaternary: assembly of multiple polypeptides into a functional protein.

Channel Proteins

Channel proteins are integrated throughout neuronal membranes, allowing ion transport and creating selectivity and gating.
Ion pumps are specialized channel proteins using ATP energy to facilitate neuronal signaling.
Dysfunction in channel proteins can lead to various neurological disorders, including epilepsy and congenital insensitivity to pain.

Ion Movement

Diffusion of dissolved ions leads to equal distribution, with ions flowing down concentration gradients through permeable channels.
Electrical behavior influences ion movement; charges are attracted and create an electrical potential difference across membranes.
Ion conductance and resistance govern the ease of charge movement, Halting conduction when resistance is too high.

Membrane Permeability

Neuronal membranes exhibit differential permeability:
- Slightly permeable to Na+
- 25 times more permeable to K+ (due to greater availability of leakage channels)
- Permeable to Cl–, leading to negative internal charge.
The sodium-potassium pump is crucial for maintaining resting membrane potential by expelling three Na+ ions for every two K+ ions brought in.

Resting Membrane Potential

Results from differences in ion concentration and plasma membrane permeability.
Neuronal membranes are more permeable to K+ ions, establishing a negative internal environment.
Changes in external K+ concentration significantly affect membrane potential.

Principles of Electricity

Membrane potential refers to voltage across neuronal membranes, critical in neuronal excitability.
Equilibrium potential (Eion) occurs when there’s no net ion movement, balancing ionic concentration gradients across membranes.
Opposite charges require energy to remain separated; current flows from high to low voltage due to differences in electrical potential.

The Nernst Equation

The equation calculates equilibrium potential (Eion) based on:
- Ion charge
- Temperature
- Ion concentration ratios across the membrane.
K+ ions are primarily concentrated within the cell, whereas Na+ and Ca2+ ions are more abundant outside.

Ion Regulation Mechanisms

Sodium-potassium pump actively moves ions against concentration gradients (3 Na+ out, 2 K+ in).
Calcium pumps are responsible for transporting Ca2+ out of the cytosol.
Energy-intensive process, consuming up to 70% of total brain ATP.

Key Takeaway

Understanding ion movement and membrane dynamics is crucial for grasping neuronal signaling processes and disease mechanisms.

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Description

This quiz covers key concepts from Zhou's 2020 paper regarding the behavior of ions in gated channels and their effect on membrane potential. Explore how selective permeability in potassium channels influences resting membrane potential and the role of concentration and electrical gradients in ion diffusion.