How does a cell membrane control the passage of molecuels into and out of a cell?

Answer 1

Through something called "Selective permeability", Which means that the cell recognize elements from outside.

Water passes through almost every cell membrane without energy, as well as some nutriants.

Minerals as sodium and Potassium have pumps on cell membrane.

Other substances pass according to many parameters including, cell needs, nature (lipophilic or hydrophilic) of the substance in question, osmotic pressure inside and outside the cell and ofcourse the type of the cell and its location.

IN ADDITION:Its called osmosis, through a permeable membrane. Imagine why your body near your stomach can separate blood, water, urine and other bodily fluids without mixing them up. It's called osmosis. Some fluids are interstitial, meaning they can pass through a membrane. The membranes determine which fluids can pass through because of the size of the holes in them.

Answer 2

Well, it does it in two ways. The first way is that the cell membrane will block out anything that is too large to pass through. Think of it as an elephant trying to squeeze through your home's front door. It's just not going to happen without damaging the cell. However most molecules & such will be small enough to penetrate the cell walls. The other way the membrane keeps things out is via a chemical signature of sorts. Think of this as the key to your home. If you don't have that key, you can't enter. The only bad thing is that many times bad stuff will be able to trick your cell membrane into believing that it's something that should be there & penetrate the membrane walls. Bacteria & bad stuff can also penetrate in other ways, though. Some germs are literally able to "drill" their way through your cell walls! Icky, huh?

Answer 3

The cell membrane functions as a barrier that makes it possible for the cytoplasm to maintain a different composition from the material surrounding the cell. The unit membrane is freely permeable to water molecules but very impermeableto ions and charged molecules. It is permeable to small molecules in inverse proportion to their size but in direct proportion to their lipid solubility. It contains various pumps and channels made of specific transverse membrane proteins that allow concentration gradients to be maintained between the inside and outside of the cell. For example, there is a cationicpump that actively extrudesodium ions (Na+) from the cytoplasm and builds up a concentration of potassium ions (K+) within it. The major anions inside the cell are chlorineions (Cl−) and negatively charged protein molecules, the latter of which cannot penetratethe membrane. The presence of the charged protein molecules leads to a buildupof electroosmotic potential across the membrane. Action potentials result from the transientopening of Na+ or calcium ion (Ca2+) channels depolarizing the membrane, followed by an opening of K+ channels leading to repolarization. This is one of the most important functions of membranes, since it makes it possible for the brain to work by sending or receiving signals sent over nerve fibers for great distances, as well as many other things. See also biopotentials-and-ionic-currents.

The plasma membrane contains numerous receptor molecules that are involved in communication with other cells and the outside world in general. These respond to antigen, hormones, and neurotransmitters in various ways. For example, thymuslymphocytes (T cells) are activated by attachment of antigens to specific proteins in the external surfaces of the T cells, an important part of the immune responses of an organism. Hormones such as epinephrineand glucagonattach to a receptor-proteinin the surfaces of cells and cause the activation of adenylate-cyclase, which in turn causes the formation of cyclic adenosinemonophosphate. Neurotransmitters attach to the postsynaptic-membranein synapsisand mediatethe transfer of information between neuron-1. There is a class of membrane proteins called cell adhesionmolecules, components of the outer surfaces of cell membranes in the developing nervous system, that is thought to be involved in guiding embryonicdevelopment.

Answer 4

Yes it does and it does so with only the efficiency that Biochemistry, from all of the three billion years of experience It has, has.

Answer 5

All cells do not have a cell wall. The only cells that have cell walls are plant cells. All cells have cell membranes that control what goes in and out of the cell.

Answer 6

most cell membranes are permeable,which will allow sodium and potasium to flow across the membrane in an osmotic condition. homeostatis is term in keeping the body in balance.

Answer 7

The cell wall is only in plants, and it gives the plants structure. The cell membrane controls the movement of substances entering and leaving the cell.

Answer 8

the cell wall or membrane

Answer 9

the cell membrane

Answer 10

Plasma membrane .