[serotonin]

Electrical impulses are the cause of the heartbeat and arise from a combination of electrochemistry and the properties of semipermeable cell membranes regarding a number of physiologically important ions (Na+,K+,Ca2+). The concentrations of these ions differ for intracellular (ICF) and extracellular fluids (ECF). In cardiac muscle cells the ICF and ECF concentrations of K+ ions are 134 and 4mM, respectively. The difference in ion concentration between ICF and ECF liquids produces a concentration cell. Is the K+ ion insertion process spontaneous? Explain based on the definition of concentration cell.

Can anyone explain to me if this really is a spontaneous process? In a concentration cell, the spontaneous movement of ions occurs from an area of lower concentration to an area of higher concentration. In the case of K+ ions in cardiac muscle cells, the concentration gradient favors the movement of K+ ions from the intracellular fluid (ICF) where the concentration is higher (134mM) to the extracellular fluid (ECF) where the concentration is lower (4mM). Doesn't that make it non spontaneous? Thanks for any help

[Babcock_Hall]

One, your post does not discuss the membrane potential.  Two, can you explain the difference between facilitated diffusion and active transport?

[NotSoSure]

Firstly, thank you for taking the time to reply to this post.
Facilitated diffusion: molecules move from the region of higher concentration to the region of lower concentration assisted by a carrier.
Active transport: movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration. => This is more of a concentration cell..
Also Q=(134mM)/(4mM) for the info given which makes it Q>1?

[Babcock_Hall]

A couple of things:  active transport requires an energy source, and with charged molecules, one has to take into account both concentration and membrane potential to assess whether the process is favorable or unfavorable thermodynamically.

[NotSoSure]

Hey thank you for your reply. If it needs a source could I say that it is probably an electrolytic cell? I have my exam in 2 hours and I'm still not sure how to answer this:'/ thanks again

[Babcock_Hall]

A particularly important enzyme in brain cells and in intestinal epithelial cells is the sodium potassium ATPase.  Using ATP hydrolysis, this enzyme transports three sodium ions from inside to outside of the cell and two potassium ions from outside to inside the cell.

[serotonin]

Thank you again so much for the reply. So I have also thought of saying it is favourable but to the left. When it is forward it is non-spontaneous. Also is saying it is electrolytic correct? Sorry if I'm asking too much, I do indeed have my exam today.. :'/ thank you again i appreciate your replies

[Babcock_Hall]

Under the assumption that the membrane potential is zero, moving potassium ions from outside to inside is non spontaneous.