User:Jwiggler/Semipermeable membrane

Excerpt from Semipermeable membrane with possible locations for additions

Goals: write and add three paragraphs (osmotic stress, dialysis tubing, and the intro to artificial membranes), add wiki connections and citations for each, and include new images into the paper

optional goal: after including sections, clean up some odd sentences and phrases throughout the rest of the page.

Found 2-3 citations for each of the 3 paragraphs I'll be adding

Osmotic Stress quotes and sources:

Due to being semipermeable, the lipid bilayer is subject to osmotic pressure. (fundamentals) When the solutes around a cell becomes more or less concentrated, osmotic pressure causes water to flow out of or into the cell to equilibrate. (osmoregulation) This osmotic stress inhibits cellular functions and molecules, such as DNA, cell membrane assembly, and protein systems, which are dependent on the activity of water in the cell. (intracellular osmotic) Osmoregulation is the method by which cells counteract osmotic stress, and includes osmosensory transporters in the membrane that allow K+ and other molecules to flow through the membrane. (osmoregulation).

Dialysis:

Hemodialysis is a technique used to purify blood in the case of kidney failure. It is based on using a semipermeable membrane to remove waste before returning the purified blood to the patient. (cellulose) Differences in the semipermeable membrane, such as size of pores, change the rate and identity of removed molecules. Traditionally, cellulose membranes were used, but they could cause inflammatory responses in patients. More expensive synthetic membranes have been developed that are more biocompatible and lead to fewer inflammatory responses. (membranes) However, despite the increased biocompatibility, synthetic membranes have not been linked to decreased mortality. (cellulose)

Artificial:

Artificial semipermeable membranes see wide usage in research and the medical field. Artificial lipid membranes can easily be manipulated and experimented upon to study biological phenomenon (synthetic). Other artificial membranes include those involved in drug delivery, dialysis, and bioseparations.(medical)

...............

Biological membranes[edit]
An example of a biological semi-permeable membrane is the lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. A group of phospholipids (consisting of a phosphate head and two fatty acid tails) arranged into a double layer, the phospholipid bilayer is a semipermeable membrane that is very specific in its permeability. The hydrophilic phosphate heads are in the outside layer and exposed to the water content outside and within the cell. The hydrophobic tails are the layer hidden in the inside of the membrane. Cholesterol molecules are also found throughout the plasma membrane and act as a buffer of membrane fluidity. The phospholipid bilayer is most permeable to small, uncharged solutes. Protein channels are embedded in or through phospholipids, and, collectively, this model is known as the fluid mosaic model. Aquaporins are protein channel pores permeable to water.

Cellular communication[edit]
Information can also pass through the plasma membrane when signaling molecules bind to receptors in the cell membrane. The signaling molecules bind to the receptors, which alters the structure of these proteins. A change in the protein structure initiates a signalling cascade. The G protein-coupled receptor signalling provides is an important subset of such signalling processes.

Osmoregulation [edit][edit] (add links to osmotic stress and osmotic pressure)
Due to being semipermeable, the lipid bilayer is subject to osmotic pressure. (fundamentals) When the solutes around a cell becomes more or less concentrated, osmotic pressure causes water to flow out of or into the cell to equilibrate. (osmoregulation) This osmotic stress inhibits cellular functions and molecules, such as DNA, cell membrane assembly, and protein systems, which are dependent on the activity of water in the cell. (intracellular osmotic) Osmoregulation is the method by which cells counteract osmotic stress, and includes osmosensory transporters in the membrane that allow K+ and other molecules to flow through the membrane. (osmoregulation).

Artificial membranes[edit]
Artificial semipermeable membranes see wide usage in research and the medical field. Artificial lipid membranes can easily be manipulated and experimented upon to study biological phenomenon (synthetic). Other artificial membranes include those involved in drug delivery, dialysis, and bioseparations.(medical)

Reverse-osmosis
The bulk flow of water through a selectively permeable membrane because of an osmotic pressure difference is called osmosis. This allows only certain particles to go through including water and leaving behind the solutes including salt and other contaminants. In the process of reverse osmosis, water is purified by applying high pressure to a solution and thereby push water through a thin-film composite membrane (TFC or TFM). These are semipermeable membranes manufactured principally for use in water purification or desalination systems. They also have use in chemical applications such as batteries and fuel cells. In essence, a TFC material is a molecular sieve constructed in the form of a film from two or more layered materials. Sidney Loeb and Srinivasa Sourirajan invented the first practical synthetic semi-permeable membrane. Membranes used in reverse osmosis are, in general, made out of polyamide, chosen primarily for its permeability to water and relative impermeability to various dissolved impurities including salt ions and other small molecules that cannot be filtered. Cellular communication[edit]

Dialysis tubing
Hemodialysis is a technique used to purify blood in the case of kidney failure. It is based on using a semipermeable membrane to remove waste before returning the purified blood to the patient. (cellulose) Differences in the semipermeable membrane, such as size of pores, change the rate and identity of removed molecules. Traditionally, cellulose membranes were used, but they could cause inflammatory responses in patients. More expensive synthetic membranes have been developed that are more biocompatible and lead to fewer inflammatory responses. (membranes) However, despite the increased biocompatibility, synthetic membranes have not been linked to decreased mortality. (cellulose)

Other types[edit]
Other types of semipermeable membranes are cation-exchange membranes (CEMs), anion-exchange membranes (AEMs), alkali anion exchange membranes (AAEMs) and proton-exchange membranes (PEMs).