Can ordinary kitchen salt get through the cell membrane?
and if so then how come the water goes out of the cell in salty water instead of the salt going inside?
- 1 decade agoFavorite Answer
Salt (NaCl) is completely dissociated into Na+ and Cl- when in an aqueous solution. Lipid bilayers, like the ones that make up the cell membranes are not permeable to charged ions.
All cells acquire the molecules and ions they need from their surrounding extracellular fluid (ECF). There is an unceasing traffic of molecules and ions
-in and out of the cell through its plasma membrane
o Examples: glucose, Na+, Ca2+
-In eukaryotic cells, there is also transport in and out of membrane-bounded intracellular compartments such as the nucleus, endoplasmic reticulum, and mitochondria.
o Examples: proteins, mRNA, Ca2+, ATP
Two problems to be considered:
1. Relative concentrations
Molecules and ions move spontaneously down their concentration gradient (i.e., from a region of higher to a region of lower concentration) by diffusion.
Molecules and ions can be moved against their concentration gradient, but this process, called active transport, requires the expenditure of energy (usually from ATP).
2. Lipid bilayers are impermeable to most essential molecules and ions.
The lipid bilayer is permeable to water molecules and a few other small, uncharged, molecules like
oxygen (O2) and carbon dioxide (CO2). These diffuse freely in and out of the cell. The diffusion of water through the plasma membrane is of such importance to the cell that it is given a special name: osmosis.
Lipid bilayers are not permeable to:
-ions such as
K+, Na+, Ca2+ (called cations because when subjected to an electric field they migrate toward the cathode [the negatively-charged electrode])
Cl-, HCO3- (called anions because they migrate toward the anode [the positively-charged electrode])
- small hydrophilic molecules like glucose
- macromolecules like proteins and RNA
Mechanisms by which cells solve the problem of transporting ions and small molecules across their membranes:
1. Transmembrane proteins create a water-filled pore through which ions and some small hydrophilic molecules can pass by diffusion. The channels can be opened (or closed) according to the needs of the cell.
2. Active transport. Transmembrane proteins, called transporters, use the energy of ATP to force ions or small molecules through the membrane against their concentration gradient.
- Anonymous1 decade ago
Salt is NaCl, which dissolves readily in water into ions, along with tons of other electrolytes that move in and out of cells for metabolism.
The cell membrane is electrically charged in mV by the potential that exists across the membrane due to two key elements, Na and K. If you have two compartments separated by a membrane that allows water to pass, and the compartments have different concentrations of salt, water will diffuse from the less concentrated to the more concentrated compartment and balance the concentrations overtime. It's a natural flow that results from a concentration gradient.
The concentration of Na and K on the sides of the membrane determine what flows in and out, especially water. Sometimes the cell uses energy to pump these ions in and out with an active Na or K molecular pump. All depends on the state of the cell is and what it needs at the moment.
- 1 decade ago
The water leaves the cell through osmosis (the diffusion of water). A salt molecule is much much larger than a water molecule, and effectively is the reason that the water diffuses out of the cell. The salt molecules block water molecules from getting in, which means that water molecules are allowed to escape at a higher rate than they are able to enter. This is why the water exits.
Now, a salt molecule is not just a sodium atom, it is usually in a large crystal form (well large in comparison to a water molecule). Cell membranes have openings that are just big enough to allow water to flow freely between the cell and its surrounding, without the cell having to exert any force. In order for a cell to absorb something like a salt molecule, it would need to actively consume it because of its size. Salt wouldnt flow freely like water.
- AnnaLv 44 years ago
Proteins can be found in numerous places in the cell. Let's begin with the phospholipid bi layer. These proteins can exist within the cell membrane which are known as integral membrane proteins, or they can be hydophylic proteins which exist as peripheral membrane proteins which interact with other proteins. The proteins within the cell do not fall out of the cell because of the cell membrane. Cell membranes that only allow certain things to pass through are said to be selectively permeable. Proteins, because of their size go in and out of the cell through what is known as exo and endo cytosis. Unlike other molecules and substances that diffuse either through the membrane itself or by active transport, these proteins exit the cell through exo cytosis. But not any protein leaves. Depending on what type of R group is attached to the polymer, usually a polypeptide, also depends on the destination of the cell. These R groups are attached to the protein in the ER and then sent to the Golgi for shipping. Hope that helped.
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- rosieCLv 71 decade ago
Salty water has a higher concentration;of solutes than plain water. Thus thru the process of osmosis,( water moving across a semipermeable membrane) and diffusion, water in the cells goes out.
simple rule to remember is:
Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.
You have a similar question re sodium and chlorine iron. I answered that also.
- Anonymous1 decade ago
Okay, i just learned this at school. The cell membrane has pores that let some things out and other things in. Like DNA. Can it get out of your cell? No, cuz the pores are too small. Um......your ? is kinda confusin, I don't think salt can get into the cell.
- 1 decade ago
as a solid-yes if the membrane is 100 micron. As a liquid YES in any size (salt disolves ya know). To remove any trace amounts of salt pre-filter with 3 micron, go through activated carbon filter then through another 3 micron. The activated carbon has a charge that attracts salts and the after filter picks up small particles of the carbon that may try to flush through.These filters come in a single canister and flow around 3.7GPM for best results. Search CUNO FILTERS-ACTIVATED CARBON