40 Questions
What is the purpose of calculating the equilibrium potential for different ions in a cell?
To understand the driving force on the ions and how they contribute to the resting membrane potential
What is the primary driving force for the net diffusion of uncharged solutes across a cell membrane?
Concentration difference
When dealing with charged solutes (ions) across a cell membrane, what two factors must be considered to determine the driving force for net diffusion?
Concentration difference and electrical potential difference
What is the formula for the driving force on a given ion across a cell membrane?
IX = GX(Em - EX)
Which of the following statements about the resting membrane potential and action potentials is correct?
The resting membrane potential is determined by the combined driving forces of all the ions present
What is the driving force behind the generation of a diffusion potential?
Concentration gradient
If a membrane is impermeable to an ion, what happens to the generation of a diffusion potential?
It stops
What factor determines the magnitude of a diffusion potential?
Charge of the diffusing ion
How do diffusion potentials affect bulk ion concentrations in a solution?
No effect on them
What happens to net diffusion of an ion when it reaches its equilibrium potential?
It stops
What primarily establishes the resting membrane potential?
Ion diffusion potentials
Which ions make the greatest contributions to the resting membrane potential?
K+ and Cl-
What is the typical range of the resting membrane potential in most excitable cells?
-80 to -90 mV
Why is the resting membrane potential close to the equilibrium potentials for K+ and Cl−?
High permeability of K+ and Cl− at rest
How can the contribution of each ion to the membrane potential be evaluated?
Using the chord conductance equation
What is the net driving force on an ion when the actual membrane potential (Em) is more negative than the ion's equilibrium potential (EX)?
The net driving force is negative, and the ion will enter the cell if it is a cation and leave the cell if it is an anion.
What is the relationship between the actual membrane potential (Em) and the ion's equilibrium potential (EX) when the net driving force on the ion is zero?
Em is equal to EX.
How does an ion 'think' the membrane potential is too positive or too negative?
The ion senses the actual membrane potential and compares it to its own equilibrium potential.
What is the direction of ion movement when the net driving force on the ion is positive?
The ion will leave the cell if it is a cation and enter the cell if it is an anion.
What is the purpose of the ion's 'desire' to bring the membrane potential towards its equilibrium potential?
To maintain the resting membrane potential and ensure proper cell function.
What is the primary factor that determines the resting membrane potential of an excitable cell?
The diffusion of ions down their electrochemical gradients
Which of the following statements accurately describes the process of depolarization?
The membrane potential moves towards the equilibrium potential of the most permeable ion
According to the chord conductance equation, which of the following factors does NOT directly contribute to the membrane potential?
The concentration gradient of calcium ions
What is the primary function of action potentials in excitable cells?
To transmit information within the nervous system and muscle cells
Which of the following statements accurately describes the refractory period of an action potential?
It is the period during which the cell is unable to generate another action potential
What happens when two solutions separated by a semipermeable membrane have the same effective osmotic pressure?
They are isotonic
How do ion channels discriminate among ions passing through them?
By the charge of the ions
What does it mean when a solution is described as hypotonic?
It has a lower effective osmotic pressure
When open, what do ion channels permit through them?
Certain ions
In terms of charges, what type of ions do channels lined with negative charges typically permit the passage of?
Cations
How does a potential difference across a membrane affect the diffusion rate of charged solutes?
It can either accelerate or slow down the diffusion rate, depending on the charge of the solute and the direction of the potential difference.
What is the main difference between simple diffusion and facilitated diffusion?
Simple diffusion is a non-selective process, while facilitated diffusion uses membrane carriers and exhibits characteristics like saturation and stereospecificity.
What is a diffusion potential?
A potential difference generated across a membrane when charged solutes diffuse down their concentration gradient.
What happens when the concentration gradient and the charge effect are oriented in the same direction across a membrane?
They combine, resulting in an increased rate of diffusion.
Which of the following statements about facilitated diffusion is correct?
It occurs down an electrochemical potential gradient, just like simple diffusion.
In the context of ion diffusion across cell membranes, what is meant by the term 'electrochemical potential gradient'?
The combined effect of the concentration gradient and the electrical potential difference across the membrane.
Which of the following statements best describes the relationship between diffusion and the resting membrane potential in excitable cells?
The diffusion of ions across the cell membrane is responsible for generating the resting membrane potential.
What is the primary driving force for the net diffusion of charged solutes across a cell membrane?
The electrochemical potential gradient, which is the combined effect of the concentration gradient and the electrical potential difference.
In the context of ion diffusion across cell membranes, what is the significance of the membrane potential?
It contributes to the electrochemical potential gradient, which drives the diffusion of ions.
What is the primary role of facilitated diffusion in excitable cells?
To rapidly transport specific ions down their electrochemical potential gradients during action potentials.
Test your knowledge on how the resting membrane potential is established through diffusion potentials, which are influenced by concentration differences of ions across the cell membrane. Quiz covers the contribution of permeant ions and equilibrium potential.
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