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Van der waals forces

2018-12-05T12:55:42Z

180643293: referencing error

Electronic charge around an [[Atom|atom]] fluctuates, which means that charge distribution isn't symmetrical. [[Atom|Atoms]] induce complementary asymmetry in neighbouring atoms. The atoms then attract each other. Attraction increases as the two atoms come closer together until they are separated by van der waals contact distance, which is where repulsive forces become dominant because the outer [[Electron|electron]] clouds of the two [[Atom|atoms]] overlap. The effect of van der waals forces is larger for larger [[Molecule|molecules]].

As two atoms closely move towards each other at a certain distance they experience a weak attractive force know as Van der Waals attraction. This results in a distance at which attractive and repulsive forces balance out to produce an energy minimum in each atoms interaction with another non-bonded [[Element|element]]<ref name="null">Alberts, Bruce. "2." Molecular Biology of the Cell. 5th ed. New York: Garland Science, 2008. 51. Print.</ref>.

Van der Waals forces are stronger in an atom, or a molecule, with the greater number of electrons; provided that the atoms are of the same size. If the sizes are different and the number of electrons are equal then van der waals forces are stronger in the smaller atom.  

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Antiporters

2018-12-05T12:54:55Z

180643293: referencing error

In order to get certain solutes across the phospholipid bilayer, transporters are required. This can be by way of either [[Passive transport|passive transport]] or [[Active transport|active transport]]. Many transporters will move a single type of solute across the membrane, and such transporters are called [[Uniporters|uniporters]]. However there are other types of transporter that will transfer two different types of solute at a time, and antiporters are from this family of [[Ion-channel-coupled receptor|coupled transporters]]. In this family of transporters the transfer of one type of solute depends completely on the transfer of the other. When both are travelling in the same direction, it is referred to as a [[Symporter|symporter]], and an example of this would be a Na+/[[Glucose transporter|glucose transporter]]. Antiporters, however, work by carrying a solute into or out of the cell, using the electrochemical gradient of the second solute, which is travelling in the opposite direction. In other words, solute A will travel down a concentration gradient into the cell, releasing energy which is harvested by solute B and used as a driving force to be pumped out of the cell in the opposite direction, but within the same transporter. An example of such transporters is the [[Sodium-calcium Exchanger|Na+/Ca+ antiporter]], driven by the electrochemical gradient of Na+ across the membrane.

The [[Sodium potassium pump|Na+/K+ pump]], which typically pumps out 3 Na+ ions for every 2 K+ ions pumped in, is commonly thought to be an antiporter, however this is not necessarily true as both ions are in fact moving against their concentration gradient<ref>Alberts B, Johnson A, et al (2008), Molecular Biology of the Cell, 5th Edition, New York: Garland Science. Chapter 11, Membrane Transport of Small Molecules and the Electrical Properties of Membranes, pages 656-660</ref>.

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Caldesmon

2018-12-05T12:54:15Z

180643293: Error in referencing

Caldesom is a [[Protein|protein]] filament present in both smooth muscle cells and also in non muscle cells and is the equivalent of [[Troponin|troponin]] in [[Skeletal muscle|skeletal muscle cells]]<ref>[Koeppen (2008)Pysiology,6th edition: mosby elsevier] Page 272</ref>.

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Oligonucleotide

2018-12-05T12:52:55Z

180643293: Created page with " Oligonucleotides are polynucleotides made of a small number of nucleotides. Their length ranges from 13 to 25 nucleotides long<ref>News Medical Life Sciences. What is an Ol..."

Oligonucleotides are polynucleotides made of a small number of nucleotides. Their length ranges from 13 to 25 nucleotides long<ref>News Medical Life Sciences. What is an Oligonucleotide. 2018 [cited 15/12/18]; Available from: https://www.news-medical.net/life-sciences/What-is-an-Oligonucleotide.aspx</ref>. 

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