Concentration gradient force Vs. electrical gradient force

In summary, the conversation discusses action potential generation via electrochemical gradients and whether a +1 unit of concentration gradient is stronger or weaker than a +1 unit of electrical gradient. It is mentioned that the practical limit to the number of ionized K+ that can diffuse through a membrane is determined by how fast Potassium or other ions can diffuse through water. There is also mention of active transport and the likelihood of an efflux or influx of K+ occurring in a given scenario. The conversation concludes with helpful resources for further understanding, including a video on osmosis and information on neurotransmission.
  • #1
ndy890
Hi Everyone,

I was just learning about action potential generation via electrochemical gradients. I was just wondering, does anyone know whether a +1 unit of concentration gradient is stronger/weaker than a +1 unit of electrical gradient?

For example: If side-A of a split chamber had a net charge of +1, while side-B had a balanced net charge of 0. But side-B had one extra K+ ion than side-A. If the membrane was only permeable to K+ ions, the concentration gradient of side B would cause a force on the K+ ions (on side-B) to go to side-A, but the electrical gradient on side-A would cause a force on K+ ions (on side-A) to go to side-B. Which force is stronger?

What term would I have to google to learn more about the forces generated by each gradient and each marginal unit of increase/decrease of concentration/charge? - This is all very interesting to me! :)

Nate
 
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  • #2
Actually this is a pretty good first question.

I think you mean osmotic pressure for a concentration gradient. And there is a practical limit to the number of ionized K+ can diffuse through a membrane. The actual differences in either of these is only important over small distances across a membrane, limited by how fast Potassium or other ions can diffuse through water. There is also something called active transport - molecules move into or out of a cell against osmotic pressure through special structures in the membrane itself. Let's stop there for now.

Osmosis is your first choice here - video:
https://www.khanacademy.org/science/biology/membranes-and-transport/diffusion-and-osmosis/v/osmosis

The action potential in neurotransmission (how nerves "talk"to one another):
https://en.wikipedia.org/wiki/Neurotransmission This has nice graphics. Note the calcium channels.Now come and ask if you get confused.
 
  • #3
jim mcnamara said:
I think you mean osmotic pressure for a concentration gradient. And there is a practical limit to the number of ionized K+ can diffuse through a membrane. The actual differences in either of these is only important over small distances across a membrane, limited by how fast Potassium or other ions can diffuse through water. There is also something called active transport - molecules move into or out of a cell against osmotic pressure through special structures in the membrane itself.

What is the origin of this 'practical limit' to the number of ionized K+ that can diffuse though a membrane? - isn't any limit of an ion's travel from one side to the other side of the membrane just determined by the electrochemical gradient (the combined forces derived from the concentration/electrical gradients)?

If we were to exclude active transport, and just think about passive transport.. how can i determine the likelihood of whether an efflux of an influx of K+ will occur with my original question of one extra +1 net charge on side-A and one extra K+ on side-B?

My original question arose from the following picture - an example of showing the two forces in action:

figure_04_05a_labeled.jpg
 
  • #4
Your picture shows an equilibrium state and gives you the results in terms of electric potential.
http://antranik.org/movement-of-substances-across-cell-membranes/

Look for the words maximal flux in the second graphic - that is what I refer to for maximum limits. Think of it as traffic flow during rush hour, no more room for more cars (or ions) on the road sometimes.
 
  • #5
Thankyou! This was all very helpful!
 

Related to Concentration gradient force Vs. electrical gradient force

1. What is a concentration gradient force?

A concentration gradient force is a type of force that occurs when there is a difference in the concentration of a substance on either side of a membrane or barrier. This difference in concentration causes the substance to move from an area of high concentration to an area of low concentration, in order to reach equilibrium.

2. What is an electrical gradient force?

An electrical gradient force is a type of force that occurs when there is a difference in charge on either side of a membrane or barrier. This difference in charge causes ions to move from an area of high charge to an area of low charge, in order to achieve a balance of charge.

3. How are concentration gradient force and electrical gradient force different?

The main difference between concentration gradient force and electrical gradient force is the driving force behind the movement of substances. In concentration gradient force, the movement is driven by the difference in concentration, while in electrical gradient force, the movement is driven by the difference in charge.

4. How do concentration gradient force and electrical gradient force work together?

In many physiological processes, concentration gradient force and electrical gradient force work together to maintain balance and facilitate the movement of substances across membranes. For example, in nerve cells, electrical gradient force helps to create an action potential, while concentration gradient force helps to facilitate the movement of ions involved in the action potential.

5. What factors can affect the strength of concentration gradient force and electrical gradient force?

The strength of concentration gradient force and electrical gradient force can be affected by several factors, including the size of the concentration or charge difference, the permeability of the membrane, and the presence of other substances that may interact with the ions or molecules involved. Temperature and pressure can also have an impact on the strength of these forces.

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