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Facilitated diffusion

2018-10-22T11:51:18Z

170136617:

[[Image:Carier protein.jpg|right|279x121px|Carrier protein showing a conformational change]]Facilitated diffusion is the movement of [[Lipid|lipid]] insoluble molecules across the [[Phospholipid bilayer|phospholipid bilayer]] by the use of carrier proteins<ref name="null">Dee Unglaub Silverthorn (2010). Human Physiology. 5th Edition. Pearson Internation Edition. Page 145-146.</ref>.

=== Basic Features ===

The bilayer consists of lipids, therefore only lipid-soluble molecules can pass through it. This is mainly small [[Polar|polar]] uncharged [[Molecules|molecules]] and small [[Hydrophobic|hydrophobic]] molecules. Facilitated diffusion is a passive process that requires no use of external energy<ref name="null">Dee Unglaub Silverthorn (2010). Human Physiology. 5th Edition. Pearson Internation Edition. Page 145-146.</ref>. The action of facilitated diffusion is spontaneous, however, the rate of the diffusion differs according to how permeable a membrane is for each substance. Most membranes are selectively permeable so different membranes have different permeability. For example, water is diffused freely across cell membranes. Other substances, however, must pass through the lipid bilayer first.<ref>ThoughtCo. Regina Bailey. Diffusion and Passive Transport. Updated October 23 2017.[cited 5/12/17]; Available from: https://www.thoughtco.com/diffusion-and-passive-transport-373399</ref> The molecules move across the membrane from an area of high concentration to an area of low concentration. If the solute carries a net charge, for example, molecules will move down its electrochemical gradient<ref name="second">Alberts et al (2002). Molecular Biology of the Cell. 4th Edition. US Garland Science. Page 618.</ref>.Sugars and amino acids are examples of molecules that move across the [[Plasma membrane|plasma membrane]] using facilitated diffusion. Also, [[GLUT transporters|GLUT transporters]] are a group of carrier proteins that move [[Glucose|glucose]] sugars and associated [[Hexose|hexose]] sugars across the [[Plasma membrane|plasma membrane]]<ref name="null">Dee Unglaub Silverthorn (2010). Human Physiology. 5th Edition. Pearson Internation Edition. Page 145-146.</ref>.

Facilitated is characterised by the following:

*High rate of transport.
*Saturation which leads to a decrease in transport across the membrane might occur as there are a limited number of carriers which might be fully active.
*Specificity as carriers are specific for substances they transport.
*Competition with substances with structural similarity as substrate might occur.
*Temperature sensitivity and carriers can be denatured at high temperatures.
*[[Enzyme Inhibitors|Inhibition]] with drugs might occur.

=== Two major types of facilitated diffusion: ===

==== 1. Carrier proteins ====

These are [[Proteins|proteins]] that span the [[Plasma membrane|plasma membrane]] ([[Transmembrane proteins|transmembrane proteins]]) and are also known as [[Permeases|permeases]]<ref>Marieb E. (2004) Human Anatomy and Physiology, 6th edition, San Francisco: Pearson Education, inc. page 72-73</ref>. Each [[Protein|protein]] carrier is specific to bind to a complementary molecule. On one side of the membrane (higher concentration of molecules), the molecules bind to the carrier protein. The carrier then changes conformational shape, moving the binding site from one side of the membrane to the other<ref>Marieb E. (2004) Human Anatomy and Physiology, 6th edition, San Francisco: Pearson Education, inc. page 72-73</ref>, releasing the molecules on the other side of the membrane (where there is a lower concentration of the molecules)<ref name="third">Barry G. Hinwood (1992). A Textbook of Science for the Health Professions. Nelson Thornes. Page 255-256.</ref>.

==== 2. Ion channel proteins ====

Unlike carrier proteins, [[Ion channels|ion channel]] proteins have gate to control the passage of substances across the cell membrane, down their electrochemical gradient, usually by the [[Ligand-gated ion channel|ligand-gated ion channel]], [[Voltage-gated ion channel|voltage-gated ion channel]] or intracellular messenger-gated ion channel<ref>http://www.vivo.colostate.edu/hbooks/cmb/cells/pmemb/diffusion_f.html</ref>. Ion channels are integral membrane proteins ([[Hydrophobic|hydrophobic]] region) that do not require binding of solutes but only allow specific types of solutes to pass through the protein channel<ref>http://zoologysangamnercollege.yolasite.com/resources/TRANSPORT%20ACROSS%20MEMBRANE.pdf</ref>.

There are three forms of transport can with facilitated diffusion ;

*[[Uniporter|Uniport]] which transports only a single substance for example , glucose transporter.
*[[Antiporter]]Antiport which exchanges one molecule for another for example, sodium calcium exchanger (Na+/Ca2+).
*[[Symporters|Symport]] which cotransports two or more substances all in one direction for example, [[Sodium|sodium]] [[Potassium|potassium]] [[Chloride|chloride]] cotransporter (Na+/K+/Cl-).

=== '''Factors affecting rate of facilitated diffusion''' ===

#Difference in concentration between the two sides of the membrane.
#The frequency of carrier proteins available on the plasma membrane: When all carrier proteins are holding molecules they are known to be 'saturated' and are working at their maximal rate, so the rate of transport is limited by the number of carrier proteins present in the membrane<ref>Marieb E. (2004) Human Anatomy and Physiology, 6th edition, San Francisco: Pearson Education, inc. page 72-73</ref>.
#The time taken for the molecule to bind to the carrier protein.
#Type of carrier protein utilized as some carriers are also specific to similarly shaped molecules<ref name="third">Barry G. Hinwood (1992). A Textbook of Science for the Health Professions. Nelson Thornes. Page 255-256.</ref>.
#The affinity of the carrier protein for its substrate molecule<ref>Alberts et al. (2008). Molecular Biology of the Cell. Fifth Edition. US Garland Science</ref>.

=== References ===

<references />

School of Biomedical Sciences Wiki

2018-10-22T11:48:00Z

170136617:

This is a Wiki of biomedical science definitions and information that has been produced by the students of the [http://www.ncl.ac.uk/biomed/ School of Biomedical Sciences] at [http://www.ncl.ac.uk Newcastle University] and at [http://www.ncl.ac.uk/numed/ Newcastle University Medicine Malaysia (NUMed)].

The project was started in October 2010 by [https://www.staff.ncl.ac.uk/n.j.morris/ Dr Nick Morris] and the pages have been created and edited by second year undergraduate students taking the Informatics Practical, and by first year students as part of the Practical Skills in Biomedical & Biomolecular Sciences module, at our UK and Malaysian campuses.

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Propanol

2017-12-06T13:00:06Z

170136617:

Propanol is an alcohol. 

There are two isomers of propanol: 1-Propan-1-ol : CH3CH2CH2OH 2-Propan-2-ol : (CH3)2CHOH

Propanol

2017-12-06T12:59:27Z

170136617: Created page with "Propanol is an alcohol.  There are two isomers of propanol: 1-Propan-1-ol : CH3CH2CH2OH 2-Propan-2-ol : (CH3)2CHOH"

Propanol is an alcohol. 

There are two isomers of propanol: 1-Propan-1-ol : CH3CH2CH2OH 2-Propan-2-ol : (CH3)2CHOH

Protein Kinase C

2017-12-06T12:57:33Z

170136617:

 Protein kinase C, commonly abbreviated to PKC, is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and threonine amino acid residues on these proteins, or a member of this family. PKC enzymes in turn are activated by signals, such as increases in the concentration of diacylglycerol (DAG) or calcium ions (Ca2+).[1] Hence PKC enzymes play important roles in several signal transduction cascades.[2]

== References ==

[1]Wilson CH, Ali ES, Scrimgeour N, Martin AM, Hua J, Tallis GA, Rychkov GY, Barritt GJ (2015). "Steatosis inhibits liver cell store-operated Ca²⁺ entry and reduces ER Ca²⁺ through a protein kinase C-dependent mechanism". The Biochemical Journal. 466 (2): 379–90.

[2]Ali ES, Hua J, Wilson CH, Tallis GA, Zhou FH, Rychkov GY, Barritt GJ (2016). "The glucagon-like peptide-1 analogue exendin-4 reverses impaired intracellular Ca2+ signalling in steatotic hepatocytes". BBA − Molecular Cell Research. 1863: 2135–46.

Protein Kinase C

2017-12-06T12:57:16Z

170136617: Created page with " Protein kinase C, commonly abbreviated to PKC, is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphoryla..."

Cascade reaction

2017-12-06T12:54:17Z

170136617:

A cascade reaction, also known as a domino reaction or tandem reaction, is a chemical process that comprises at least two consecutive reactions such that each subsequent reaction occurs only in virtue of the chemical functionality formed in the previous step.[1]



== References ==

[1]Tietze, L. F.; Beifuss, U. Angew. Chemie Int. Ed. 1993, 32, 131–163

Cascade reaction

2017-12-06T12:53:44Z

170136617: Created page with "= Cascade Reactions =  A cascade reaction, also known as a domino reaction or tandem reaction, is a chemical process that comprises at least two consecutive reactions such ..."

= Cascade Reactions =

 A cascade reaction, also known as a domino reaction or tandem reaction, is a chemical process that comprises at least two consecutive reactions such that each subsequent reaction occurs only in virtue of the chemical functionality formed in the previous step.[1]



== References ==

[1]Tietze, L. F.; Beifuss, U. Angew. Chemie Int. Ed. 1993, 32, 131–163