The School of Biomedical Sciences Wiki - User contributions [en]

Sequence degeneracy

2018-11-05T11:10:47Z

160446287: Inserted Reference Header and corrected reference

Sequence Degeneracy occurs as a result of back translating a [[Protein sequence|protein sequence]] into a [[DNA sequence|DNA sequence]].

Degeneracy occurs when back translating a [[Protein sequence|protein sequence]] due to the many different combinations of bases that can create the same [[Amino acid|amino acid]] sequence.

However [[DNA sequences|DNA sequences]] with ambiguous bases can be accounted for using the [[IUB|IUB]] and [[IUB Complement|complement code]] to work out the correct [[Reverse translation|reverse translation]].

The protein sequence 'SCIENCE' contains the [[Amino acids|amino acids]]: Serine, Cysteine, Isoleucine, Glutamic, Asparagine, Cysteine and Glutamic respectively, however as each of these amino acids can be encoded by more than one t[[Triplet code|riplet]], ambiguity arises.

In this instance: 'SCIENCE'

*[[Serine|Serine]] = 6 possible codons
*[[Cysteine|Cysteine]] = 2 possible codons
*[[Isoleucine|Isoleucine]] = 3 possible codons
*[[Glutamic|Glutamic]] = 2 possible codons
*[[Asparagine|Asparagine]] = 2 possible codons
*[[Cysteine|Cysteine]] = 2 possible codons
*[[Glutamic|Glutamic]] = 2 possible codons

The degeneracy of the sequence can be determined through the multiplication of the number of possible [[Codons|codons]] at each amino acid on the sequence.

Degeneracy in this case is: 6 x 2 x 3 x 2 x 2 x 2 x 2 = 576

=== References: ===

Bioinformatica.upf.edu. (2005). ''SNPs in Human Selenoproteins Genes''. [online] Available at: http://bioinformatica.upf.edu/2005/projectes05/3.2.4/material.html [Last accessed 31 Oct. 2018].

Sequence degeneracy

2018-11-05T11:10:02Z

160446287:

Sequence degeneracy

2018-10-27T14:25:33Z

160446287: Took out the mistakes I missed when first making the page.

Sequence Degeneracy occurs as a result of back translating a [[Protein sequence|protein sequence]] into a [[DNA sequence|DNA sequence]].  Degeneracy occurs when back translating a [[Protein sequence|protein sequence]] due to the many different combinations of bases that can create the same [[Amino acid|amino acid]] sequnce.  However [[DNA sequences|DNA sequences]] with ambiguous bases can be accounted for using the [[IUB|IUB]] and [[IUB Complement|complement code]] to work out the correct [[Reverse translation|reverse translation]].  The protein sequence 'SCIENCE' contains the [[Amino acids|amino acids]]: Serine, Cysteine, Isoleucine, Glutamic, Asparagine, Cysteine and Glutamic respectively, however as each of these amino acids can be encoded by more than one t[[Triplet code|riplet]], ambiguity arises. In this instance: 'SCIENCE' Serine = 6 possible codons  Cysteine = 2 possible codons    Isoleucine = 3 possible codons Glutamic = 2 possible codons    Asparagine = 2 possible codons    Cysteine = 2 possible codons Glutamic = 2 possible codons  The degeneracy of the sequence can be determined through the multiplication of the number of possible [[Codons|codons]] at each amino acid on the sequence.  Degeneracy in this case is: 6 x 2 x 3 x 2 x 2 x 2 x 2 = 576  

Bioinformatica.upf.edu. (2018). SNPs in Human Selenoproteins Genes. [online] Available at:[[Javascript:void(0);/*1540564120009*/|http://bioinformatica.upf.edu/2005/projectes05/3.2.4/material.html ]]

Sequence degeneracy

2018-10-26T14:35:23Z

160446287: Added more detail to the definition and an example of how to work out degeneracy from a protein sequence

Sequence Degeneracy occurs as a result of back translating a [[Protein sequence|protein sequence]] into a [[DNA sequence|DNA sequence]].  Degeneracy occurs when back translating a [[Protein sequence|protein sequence]] due to the many different combinations of bases that can create the same [[Amino acid|amino acid]] sequnce.  However [[DNA sequences|DNA sequences]] with ambiguous bases can be accounted for using the [[IUB|IUB]] and [[IUB Complement|complement code]] to work out the correct [[Reverse translation|reverse translation]].  For example, the protein sequence 'SCIENCE' contains the [[Amino acids|amino acids]]: Serine, Cysteine, Isoleucine, Glutamic, Asparagine, Cysteine and Glutamic respectively, however as each of these amino acids can be encoded by more than one t[[Triplet code|riplet]], ambiguity arises. In this instance: 'SCIENCE' Serine = 6 possible codons  Cysteine = 2 possible codons    Isoleucine = 3 possible codons Glutamic = 2 possible codons    Asparagine = 2 possible codons    Cysteine = 2 possible codons Glutamic = 2 possible codons  The degeneracy of the sequence can be determined through the multpiplication of the number of possible [[Codons|codons]] at each amino acid on the sequence.  Degeneracy in this case is: 6 x 2 x 3 x 2 x 2 x 2 x 2 = 576  

Bioinformatica.upf.edu. (2018). SNPs in Human Selenoproteins Genes. [online] Available at:[[Javascript:void(0);/*1540564120009*/|http://bioinformatica.upf.edu/2005/projectes05/3.2.4/material.html ]]

File:IUAPAC.jpg

2018-10-26T13:45:14Z

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A table to represent both distinguished and ambiguous bases within codon combinations available at [http://bioinformatica.upf.edu/2005/projectes05/3.2.4/material.html bioinformatica.upf.edu/2005/projectes05/3.2.4/material.html]

File:IUAPAC.jpg

2018-10-26T13:40:44Z

160446287: A table to represent both distinguished and ambiguous bases within codon combinations.

A table to represent both distinguished and ambiguous bases within codon combinations.

Antibiotic resistance

2017-12-03T15:39:54Z

160446287: Expanded with additional information, added all references, edited and inserted links

Antibiotic resistance is when a strain of [[Bacteria|bacteria]] is not affected by an [[Antibiotic|antibiotic]], as such the bacteria in question can colonise tissues and cause disease in the presence of antibiotics. This is becoming an increasing problem in many infections and some strains have developed [[Multi-drug resistance (MDR)|multiple drug resistance]] meaning they are resistant to a range of different antibiotic treatments and combinations. An example of such a virus is MRSA ([[Methicillin-restistant Staphylococcus aureus (MRSA)|methicillin-restistant ''Staphylococcus aureus'']]) which is very difficult to treat and is causing increasing problems in places such as hospitals where open wounds are present and many of the patients have weakened [[Immune system|immune systems]]. They are therefore more vulnerable to infection. <ref>Chambers H, DeLeo F. Waves of resistance: Staphylococcus aureus in the antibiotic era. Nature Reviews Microbiology [Internet]. 2009 [cited 3 December 2017];7(9):629-641. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871281/</ref> One way in which bacteria can become resistance to the antibiotic properties of a drug involves the exposure of the organism to a non-lethal quantity of the drug which will allow the bacteria to adapt to negate the effect of the drug and providing it survives will provide a level of resistance for future exposures and future generation through vertical gene transfer. <ref>Silva J. Mechanisms of antibiotic resistance. Current Therapeutic Research. 1996;57(13):30-35.</ref>Bacteria can also pass these properties to other bacteria through horizontal gene transfer involving the processed of [[Conjugation|bacterial conjugation]], the exchange of genetic material through use of a sex pilus, [[Transformation|bacterial transformation]] the uptake of free DNA from the environment, usually plasmid DNA, or [[Transduction|bacterial transduction]] where the bacteria is injected with foreign DNA through use of a [[Bacteriophage|bacteriophage]], all can result in antibiotic resistance being passed on. <ref>Barlow M. What Antimicrobial Resistance Has Taught Us About Horizontal Gene Transfer. Horizontal Gene Transfer [Internet]. 2009 [cited 3 December 2017];1(1):397-411. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19271198</ref>

 <references />

Cytotoxic T-cells

2017-12-03T15:18:15Z

160446287: Edited reference and added hyphen where necessary

Also known as a killer T-cell. These cells kill host cells that have become infected by some sort of intracellular [[Pathogen|pathogen]] <ref>alberts, B (2008). molecular biology of the cell. USA: garland science. glossary</ref>.

The cytotoxic T-cells can trigger an endogeneous pathway within the target cell leading to [[Apoptosis|apoptosis]]. This is due to the cytotoxic T-cells releasing "preformed effector molecules" <ref>Janeway CA Jr, et al.;2001</ref><ref>Janeway C. Immunobiologie. 5th ed. Paris: De Boeck; 2003.</ref>

=== References ===

<references />

Clotting factors

2017-12-03T15:13:27Z

160446287: Reference added

Blood coagulation is the transformation of [[Blood|blood]] as a liquid into a solid gel-like blood "clot". A clot is formed when [[Platelets|platelets]] stick to [[Collagen|collagen]] exposed by a disrupted blood vessel lining. Other platelets then bind to the initial platelets to form what is called a [[Platelet plug|platelet plug]]. The platelet plug is limited to the disrupted area and does not spread to the normal unaffected tissue. Clotting occurs on top of the platelet plug when [[Fibrinogen|Fibrinogen]] (a large soluble [[Protein]]) is converted into [[Fibrin monomers|Fibrin monomers]] (an insoluble thread-like molecule) by [[Thrombin|thrombin]]. Fibrin monomers are then crosslinked into Fibrin polymers in the presence of [[Factor XIIIa|factor XIIIa]] and [[Calcium|Ca2+]]. <ref>Factor XIIIa [Internet]. Pathologyoutlines.com. 2017 [cited 3 December 2017]. Available from: http://pathologyoutlines.com/topic/stainsfactorxiiia.html</ref> <references />

COX enzyme

2017-12-03T15:08:01Z

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COX or cyclo-oxygenase enzymes produce prostaglandins which promotes [[Inflammation|inflammatory]] actions such as pain, inflammation and fever essential for the mechanisms involed in healing and recovery<ref>Omudhome Ogbru P. NSAIDs: Drug List, Names, and Side Effects [Internet]. MedicineNet. 2017 [cited 1 December 2017]. Available from: https://www.medicinenet.com/nonsteroidal_antiinflammatory_drugs/article.htm</ref> There are two COX enzymes, [[COX-1|COX-1]] and [[COX-2|COX-2]]. They can be inhibited by [[Non-steroidal anti-inflammatory drugs|non-steroidal anti-inflammatory drugs]] (NSAIDS) such as ibuprofen, paracetamol and mefanamic acid. The analgesic action of nonsteroidal anti-inflammatory drugs (NSAIDs) has been explained on the basis of their inhibition of the these enzymes, COX-1 and COX-2, that synthesise prostaglandins.

*COX-1 is a constitutive member of normal cells and COX-2 is induced in inflammatory cells.
*Inhibition of COX-2 activity represent the most likely mechanism of action for [[Non-steroidal anti-inflammatory drugs|NSAID]]-mediated analgesia, while the ratio of inhibition of COX-1 to COX-2 by NSAIDs should determine the likelihood of adverse effects. In addition, some NSAIDs inhibit the lipoxygenase pathway, which may itself result in the production of algogenic [[Metabolites|metabolites]]. Interference with[[G-protein|G-protein]]-mediated signal transduction by [[Non-steroidal anti-inflammatory drugs|NSAIDs]] may form the basis of an [[Analgesic|analgesic mechanism]] unrelated to inhibition of prostaglandin synthesis.<ref>Cashman J. The Mechanisms of Action of NSAIDs in Analgesia. Drugs [Internet]. 1996 [cited 3 December 2017];52(Supplement 5):13-23. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8922554</ref>

 

=== References ===

<references />

COX enzyme

2017-12-03T15:06:56Z

160446287: Additional information on mechanism, links and references added,

COX or cyclo-oxygenase enzymes produce prostaglandins which promotes [[Inflammation|inflammatory]] actions such as pain, inflammation and fever essential for the mechanisms involed in healing and recovery<ref>Omudhome Ogbru P. NSAIDs: Drug List, Names, and Side Effects [Internet]. MedicineNet. 2017 [cited 1 December 2017]. Available from: https://www.medicinenet.com/nonsteroidal_antiinflammatory_drugs/article.htm</ref>.There are two COX enzymes, [[COX-1|COX-1]] and [[COX-2|COX-2]].They can be inhibited by [[Non-steroidal anti-inflammatory drugs|non-steroidal anti-inflammatory drugs]] (NSAIDS) such as ibuprofen, paracetamol and mefanamic acid. The analgesic action of nonsteroidal anti-inflammatory drugs (NSAIDs) has been explained on the basis of their inhibition of the these enzymes, COX-1 and COX-2, that synthesise prostaglandins.

*COX-1 is a constitutive member of normal cells and COX-2 is induced in inflammatory cells.
*Inhibition of COX-2 activity represent the most likely mechanism of action for [[Non-steroidal_anti-inflammatory_drugs|NSAID]]-mediated analgesia, while the ratio of inhibition of COX-1 to COX-2 by NSAIDs should determine the likelihood of adverse effects. In addition, some NSAIDs inhibit the lipoxygenase pathway, which may itself result in the production of algogenic [[Metabolites|metabolites]]. Interference with[[G-protein|G-protein]]-mediated signal transduction by [[Non-steroidal_anti-inflammatory_drugs|NSAIDs]] may form the basis of an [[Analgesic|analgesic ]]mechanism unrelated to inhibition of prostaglandin synthesis.<ref>Cashman J. The Mechanisms of Action of NSAIDs in Analgesia. Drugs [Internet]. 1996 [cited 3 December 2017];52(Supplement 5):13-23. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8922554</ref>

 

=== References ===

<references />

Smooth muscle cell

2017-12-03T14:51:58Z

160446287: image added

Smooth muscle has elongated spindle shaped cells with a single [[Nucleus|nucleus]]. Unlike [[Skeletal Muscle|skeletal muscle]], which appears [[Striated muscle|striated]] when stained and viewed under a light microscope, the contractile filaments in smooth muscle cells aren't arranged in such an ordered, linear way. The contractile proteins are [[Actin|actin]] and [[Myosin|myosin]], the same as in skeletal muscle cells.The amount of [[Myosin|myosin]] in smooth muscle cells is considerably less than in cells of skeletal muscle; the ratio of [[Actin|actin]] to [[Myosin|myosin]] is about 15:1 for smooth muscle, compared to only 2:1. Smooth muscle cells are located within the walls of tubular or hollow organs or vessels for structural support. These can be divided into subtypes of smooth muscle cells; those in the vascular system, [[Respiratory system|respiratory system]], intestines, the eye and reproductive organs.<ref>Alberts, B. (2002). Molecular biology of the cell (4th ed.). New York: Garland Science.</ref> [[Image:Smooth muscle.jpg]]   [[Muscle contraction|Contraction]] of smooth muscle is controlled by the [[Autonomic Nervous System|autonomic nervous system]], meaning its movements are primarily involuntary. However, as opposed to skeletal muscle, it can also be controlled by chemical and physical signals. This means that either an action potential is required to cause a change in membrane potential, or the opening of stretch-mediated ion protein channels; they both bring about contraction.<ref>American Physiology Society. Advances in Physiology Education: Smooth Muscle Contraction and Relaxation (2014) Available at: http://advan.physiology.org/content/27/4/201</ref>

Smooth muscle cell contraction is regulated by the calcium binding protein [[Calmodulin|calmodulin]]. When there is an increase in calcium ion concentration, [[Calmodulin|calmodulin attaches]] to [[Caldesmon|caldesmon]], which is an [[Actin|actin]]-binding protein. [[Caldesmon|Caldesmon]] normally blocks the [[Myosin|myosin]]-binding sites on [[Actin filaments|actin filaments]]. As [[Calmodulin|calmodulin]] attaches to caldesmon it releases actin, causing the [[Myosin|myosin]] heads to bind to the [[Actin filaments|actin filaments]]. The globular heads that protrude from the [[Myosin|myosin molecule]] bind to the [[Actin|actin]] filament which forms crossbridges. The [[Myosin|myosin moves]] along the actin and then releases from the actin (also requiring the use of ATP). [[Contraction|Contraction]] is initiated by calcium-regulated [[Phosphorylation|phosphorylation]] of myosin<ref>Walter F. Boron, E. L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier.</ref>. Apart from calcium ions, smooth muscle activity can also be regulated by external signalling molecules, for example, [[Adrenaline|adrenaline]]. When [[Adrenaline|adrenaline]] binds to the receptor and changes its shape, this in turns alters the structure of the [[G-protein|G- protein]] that binds to the receptor. This causes an increase of level of [[Cyclic AMP|cyclic AMP]] inside the cell, which activates [[Protein kinase|protein kinase]]. This then phosphorylates and inactivates [[Myosin light chain kinase|myosin light chain kinase]], eventually leading to relaxation of the smooth muscle. Smooth muscle contraction is significantly slower than skeletal muscle contraction. It usually takes nearly a second whereas skeletal muscle takes a few milliseconds<ref>Silverthorn D, Johnson B, Ober W and Silverthorn C. (2012) Human Physiology: An Integrated Approach. 6th Edition</ref>. 

=== References ===

<references />

File:Smooth muscle.jpg

2017-12-03T14:46:55Z

160446287: Image of smooth muscle under a microscope

Image of smooth muscle under a microscope

Smooth muscle cell

2017-12-03T14:46:22Z

160446287: Added links and rearranged references,

Smooth muscle has elongated spindle shaped cells with a single [[Nucleus|nucleus]]. Unlike [[Skeletal Muscle|skeletal muscle]], which appears [[Striated muscle|striated]] when stained and viewed under a light microscope, the contractile filaments in smooth muscle cells aren't arranged in such an ordered, linear way. The contractile proteins are [[Actin|actin]] and [[Myosin|myosin]], the same as in skeletal muscle cells.The amount of [[Myosin|myosin]] in smooth muscle cells is considerably less than in cells of skeletal muscle; the ratio of [[Actin|actin]] to [[Myosin|myosin]] is about 15:1 for smooth muscle, compared to only 2:1. Smooth muscle cells are located within the walls of tubular or hollow organs or vessels for structural support. These can be divided into subtypes of smooth muscle cells; those in the vascular system, [[Respiratory system|respiratory system]], intestines, the eye and reproductive organs.<ref>Alberts, B. (2002). Molecular biology of the cell (4th ed.). New York: Garland Science.</ref>

[[Muscle contraction|Contraction]] of smooth muscle is controlled by the [[Autonomic Nervous System|autonomic nervous system]], meaning its movements are primarily involuntary. However, as opposed to skeletal muscle, it can also be controlled by chemical and physical signals. This means that either an action potential is required to cause a change in membrane potential, or the opening of stretch-mediated ion protein channels; they both bring about contraction.<ref>American Physiology Society. Advances in Physiology Education: Smooth Muscle Contraction and Relaxation (2014) Available at: http://advan.physiology.org/content/27/4/201</ref>

Smooth muscle cell contraction is regulated by the calcium binding protein [[Calmodulin|calmodulin]]. When there is an increase in calcium ion concentration, [[Calmodulin|calmodulin attaches]] to [[Caldesmon|caldesmon]], which is an [[Actin|actin]]-binding protein. [[Caldesmon|Caldesmon]] normally blocks the [[Myosin|myosin]]-binding sites on [[Actin filaments|actin filaments]]. As [[Calmodulin|calmodulin]] attaches to caldesmon it releases actin, causing the [[Myosin|myosin]] heads to bind to the [[Actin filaments|actin filaments]]. The globular heads that protrude from the [[Myosin|myosin molecule]] bind to the [[Actin|actin]] filament which forms crossbridges. The [[Myosin|myosin moves]] along the actin and then releases from the actin (also requiring the use of ATP). [[Contraction|Contraction]] is initiated by calcium-regulated [[Phosphorylation|phosphorylation]] of myosin<ref>Walter F. Boron, E. L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier.</ref>. Apart from calcium ions, smooth muscle activity can also be regulated by external signalling molecules, for example, [[Adrenaline|adrenaline]]. When [[Adrenaline|adrenaline]] binds to the receptor and changes its shape, this in turns alters the structure of the [[G-protein|G- protein]] that binds to the receptor. This causes an increase of level of [[Cyclic AMP|cyclic AMP]] inside the cell, which activates [[Protein kinase|protein kinase]]. This then phosphorylates and inactivates [[Myosin light chain kinase|myosin light chain kinase]], eventually leading to relaxation of the smooth muscle. Smooth muscle contraction is significantly slower than skeletal muscle contraction. It usually takes nearly a second whereas skeletal muscle takes a few milliseconds<ref>Silverthorn D, Johnson B, Ober W and Silverthorn C. (2012) Human Physiology: An Integrated Approach. 6th Edition</ref>. 

=== References ===

<references />

Nucleoplasm

2017-12-03T14:37:07Z

160446287: Fact check- hyaloplasm

The protoplasm present in the [[Nucleus|nucleus]] of [[Eukaryotic|eukaryotic]] [[Cells|cells]]. It is a highly viscous liquid enveloped by the [[Nuclear membrane|nuclear membrane]], regulating passage of [[Molecules|molecules]] between the nucleoplasm and the [[Cytoplasm|cytoplasm]]<ref>Del Mar College. Visual summary of Eukaryotic cells. 2016 [ cited 04/12/16] Available from: http://dmc122011.delmar.edu/nsci/biology/faculty/brower/powerLectures/ch4/chapter4_part2.pdf</ref>. It consists mainly of [[Water|water]], dissolved ions, and a complex mixture of other molecules. 32% of all human [[Proteins|proteins]] have experimentally shown to be present within the nucleoplasm<ref>The Human Protein Atlas. The Human Cell: Nucleoplasm. 2016 [cited 04/12/16] Available from: http://www.proteinatlas.org/humancell/nucleoplasm</ref>

=== Function ===

The nucleoplasm acts as a suspension medium for components of the nucleus including the [[Nucleolus|nucleolus]], and [[Chromatin|chromatin]]. [[Nucleotides|Nucleotides]] required for [[DNA replication|DNA replication]] and [[Enzyme|enzymes]] involved in other nuclear processes are also found dissolved within the nucleoplasm<ref>Del Mar College. Visual summary of Eukaryotic cells. 2016 [ cited 04/12/16] Available from: http://dmc122011.delmar.edu/nsci/biology/faculty/brower/powerLectures/ch4/chapter4_part2.pdf</ref>. The nucleoplasm plays a role in the maintenance of the shape and structure of the nucleus<ref>Del Mar College. Visual summary of Eukaryotic cells. 2016 [ cited 04/12/16] Available from: http://dmc122011.delmar.edu/nsci/biology/faculty/brower/powerLectures/ch4/chapter4_part2.pdf</ref>. The [[Nuclear matrix|nuclear matrix]] is present within the nuclear hyaloplasm, the liquid component of the nucleoplasm<ref>UFRGS. Subcellular structures. 2016 [cited 04/12/16] Available from: http://www.ufrgs.br/imunovet/molecular_immunology/compartment.htm</ref>

=== References ===

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Cardiac musle

2017-12-03T14:22:17Z

160446287: Additional information, added reference and inserted necessary spaces

Cardiac muscle is one of the three types of [[Muscle|muscle]] in mammals. It is myogenic [[Striated muscle|striated muscle]] that forms the structure of the [[Heart|heart]]. Cardiac muscle contracts like skeletal muscle; the shortening of the sacromere causes the contraction on the muscle.<ref>Alberts, B. et al 'Molecular Biology of the Cell' Fifth Edition (2008) p.1031, Abingdon, Garland Science, Taylor &amp;amp;amp;amp;amp; Francis Group LLC</ref>

The structure of cardiac muscle are long, cylindrical cells with one, sometimes two, nuclei. They branch out into 'Y' shapes. There is a rich blood supply provided by the vast [[Capillary|capillary]] network. This is necessary due to the high level of energy required for the typical heart function. This capillary network is supported by connective tissue between these cardiac muscle fibres. There are also far more [[Mitochondria|mitochondria]] in cardiac muscle than typical skeletal muscle as the production of ATP is essential to cardiac muscle function, unlike most muscles in the body they are constantly contracting and relaxing thus requiring far more energy than in skeletal muscle. <ref>Lemieux H, Hoppel C. Mitochondria in the human heart. Journal of Bioenergetics and Biomembranes [Internet]. 2009 [cited 3 December 2017];41(2):99-106. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19353253</ref>

Between each cardiac muscle filament, there a intercalated discs found at the junction between cells. These discs are formed of [[Desmosomes|desmosomes]] and they hold the cells together over the [[Gap Junction|gap junctions]].This allows [[Action potentials|action potentials]] to move with lower resistance. <ref>Queen Margaret University (2012) 'Excitable Tissues' [Online] Available at http://www.qmu.ac.uk/hn/appliedscience/D%20Excitable%20Tissues/cardiac_muscle.htm [Accessed on 27/11/2014]</ref>

=== References ===

<references />

Cholesterol

2017-12-03T14:14:10Z

160446287:

[[Cholesterol|Cholesterol]] is a steroidal lipid found in all animals in the [[Plasma_membrane|plasma membrane]], and can be present in some intracellular membranes but normally at lower levels.

=== Structure: ===

[[Cholesterol|Cholesterol]] is made up of three sections, the [[Steroid|steroid]] component at one end attached to four [[Hydrocarbon|hydrocarbon]] rings, on the other end is a hydroxly group.

=== Function: ===

Cholesterol is positioned in the [[Lipid_bi-layer|lipid bilayer ]]parallel to the fatty acid chains of the [[Phosphlipid|phosopholipids]], and the [[Hydrophilic|hydrophilic]] hydroxyl group interacts with the hydrophilic head of the phospholipid, <ref>Berg J, Tymoczko J, Stryer L (2012), Biochemistry, seventh edition, W.H. Freeman and Company, Basinstoke. p362</ref>. Cholesterol is needed in the membrane to alter the fluidity of the bilayer which affects the function of the membrane and therefore the specific cell. Cholesterol can increase the rigidity of the cell membrane, by doing this the membrane becomes less permeable to water soluble molecules. However it is important to remember that it doesn't make the membranes less fluid.  At high concentration cholesterol prevents the hydrocarbon chains in the membrane from crystallizing. High concentrations are found in most eukaryotic cells for example the [[Liver cells|liver cell and]] [[Red blood cells|red blood cells.]] <ref>Alberts, Johnson, Lewis, Morgan, Raff, Roberts, Walter (2015). Molecular Biology of The Cell. 6th ed. New York: Garland Science. 571.</ref> It is also inportant in the production of steriodal hormones, including male and female sex hormones, [[Vitamin D|Vitamin D]] and producing [[Bile Salts|Bile Salts in]] the Liver. It can also plan an important role in the [[Myelin Sheath|Myelin Sheath]] in [[Neuron|neurones]] <ref>Miezam Cayrol, Enzine Articles. (2007, Dec 12) http://ezinearticles.com/?Knowing-Cholesterol-and-Its-5-Main-Functions&amp;amp;amp;amp;amp;amp;amp;amp;amp;id=869678</ref>

There are two main types of Cholesterol and two minor types:

==== Major forms: ====

LDL - [[Low density lipoproteins|Low density lipoproteins]] (good cholesterol) 

HDL - [[High density lipoproteins|High density lipoproteins]] (bad cholesterol) 

==== Minor forms: ====

VLDL - Very low density lipoproteins  (very bad forms of cholesterol)

Chylomicrons - carry very little cholesterol, but a lot of triglycerides. 

Cholesterol in high density forms can cause such problems as cardiovascular disease and in excess lower density forms can cause Atherosclerosis.

Cholesterol levels can increase with: 

*Diets high in saturated fats or trans fats
*Obesity
*A sedentary lifestyle <ref>WebMD, LLC (2009) http://www.webmd.boots.com/cholesterol-management/guide/understanding-cholesterol-problems-basics</ref>

=== References ===

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Phosphofructokinase

2017-12-03T14:11:26Z

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Phosphofructokinase (PFK) is a fundamental [[Enzyme|enzyme]] in the [[Glycolitic pathway|glycolytic pathway]]. As the name suggests, the enzyme acts on the intermediate compound 'phosphofructose'; its proper name being [[Fructose-6-phosphate|fructose-6-phosphate]]. The suffix '[[Kinase|kinase]]' indicates its function as a phosphorylator. The product of this enzyme-subtrate interaction is [[Fructose-1,6-bisphosphate|fructose 1,6 bisphosphate]], which subsequently is [[Hydrolysed|hydrolysed]] to [[Glyceralaldehyde 3 phosphate|glyceralaldehyde 3 phosphate]] and [[Dihydroxyacetone phosphate|dihydroxyacetone phosphate]]. <ref>Phosphofructokinase - an overview | ScienceDirect Topics [Internet]. Sciencedirect.com. 2017 [cited 3 December 2017]. Available from: http://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/phosphofructokinase</ref>

PFK is an [[Allosteric enzyme|allosteric enzyme]]; meaning that its action is regulated by activator and inhibitor effector molecules; in this case [[AMP|AMP]] and [[ATP|ATP]] respectively. 

Phosphofructokinase has antagonistic action with the enzyme [[Fructose 1,6-bisphosphatase|Fructose 1,6-bisphosphatase]]; a dephosphorylator.<ref>Berg J, Tymoczko J, Stryer L, Clarke N. Biochemistry. New York: W.H. Freeman; 2002.</ref> <references />

Phosphofructokinase

2017-12-03T14:10:25Z

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Relay neuron

2017-12-03T13:54:30Z

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A relay [[Neuron|neuron]] (also known as an interneuron) passes signals between [[Neurons|neurons]].  Relay neurones are only found in the brain, visual system and [[Spinal cord|spinal cord]] acting to relay signals. They recieve a signal from one neuron and then transfer the signal to another interneuron resulting in the signal being passed to a [[Motor neuron|motor neurone]] thus driving the reaction to the [[Stimulus|stimulus. ]] <ref>Becker W., Hardin J., Bertoni G., and Kleinsmith L. (2012) Becker’s World Of The Cell, 8th Edition, San Francisco: Pearson Education. Page 365</ref>

[[Image:Interneurone.jpg]] These can be differentiated from other neurones by observing their short [[Dendrites|dendrites]] and either long or short axons..<ref>The structure and function of sensory, relay and motor neurons. [Internet]. Psychology Hub. 2017 [cited 3 December 2017]. Available from: https://psychologyhub.co.uk/the-structure-and-function-of-sensory-relay-and-motor-neurons/</ref>

=== References ===

<references />

File:Interneurone.jpg

2017-12-03T13:52:43Z

160446287: Image of a relay neuron (interneuron)

Image of a relay neuron (interneuron)

Pre RNA World

2017-12-03T13:43:24Z

160446287:

The RNA world hypothesis is based in the theory that  RNA preceded [[DNA|DNA]] at an eary stage in the evolutionary history of life on Earth, the hypothesis predicts that self-replicating RNA molecules proliferated before the evolution of DNA and proteins. Although this is heavily supported by contemporary research however it is not without its flaws. These flaws surround the stability and creation of [[RNA|RNA]]. To solve these problems a 'Pre-RNA World' was introduced. The hypothesis suggests that before RNA there was a much simpler molecule that still had "both [[Catalysts|catalytic activity]] and information storage capabilities" <ref>Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter (2008) Molecular Biology of the cell, 5th edition, New York: Garland Science p.402</ref>. There is strong evidence indicating that an RNA World did preceed a DNA world. The structure i question can be observed in the contemporary [[Ribosome|ribosome.]] The active site for [[Peptide bond|peptide-bond]] formation lies deep within a central core of RNA, whereas proteins decorate the outside of this RNA core and insert narrow extensions into it. No [[Amino acid|amino acid side]] chain comes within 18 Å of the active site. As this is the case, the [[Ribosome|ribosome]] was identified as a [[Ribozyme|ribozyme]] and it was theorised that the primitive [[Ribosome|ribosome]] could have been made entirely of RNA.<ref>Robertson M, Joyce G. The Origins of the RNA World. Cold Spring Harbor Perspectives in Biology [Internet]. 2010 [cited 3 December 2017];4(5):1-12. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3331698/</ref> Although it is widely accepted that RNA preceded DNA their is also a pre-RNA world theory in which simpler biomolecules would, through evolution, become what eventually became RNA. <ref>Klyce B. The RNA World and other origin-of-life theories. by Brig Klyce [Internet]. Panspermia.org. 2017 [cited 3 December 2017]. Available from: http://www.panspermia.org/rnaworld.htm</ref>

=== References ===

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Pre RNA World

2017-12-03T13:38:14Z

160446287:

The RNA world hypothesis is based in the theory that  RNA preceded [[DNA|DNA]] at an eary stage in the evolutionary history of life on Earth, the hypothesis predicts that self-replicating RNA molecules proliferated before the evolution of DNA and proteins. Although this is heavily supported by contemporary research however it is not without its flaws. These flaws surround the stability and creation of [[RNA|RNA]]. To solve these problems a 'Pre-RNA World' was introduced. The hypothesis suggests that before RNA there was a much simpler molecule that still had "both [[Catalysts|catalytic activity]] and information storage capabilities" <ref>Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter (2008) Molecular Biology of the cell, 5th edition, New York: Garland Science p.402</ref>. There is now strong evidence indicating that an RNA World did indeed exist on the early Earth. The smoking gun is seen in the structure of the contemporary [[Ribosome|ribosome.]] The active site for [[Peptide bond|peptide-bond]] formation lies deep within a central core of RNA, whereas proteins decorate the outside of this RNA core and insert narrow fingers into it. No [[Amino acid|amino acid side]] chain comes within 18 Å of the active site. Clearly, the [[Ribosome|ribosome]] is a [[Ribozyme|ribozyme]] and it is hard to avoid the conclusion that, as suggested by Crick, the primitive [[Ribosome|ribosome]] could have been made entirely of RNA.<ref>Robertson M, Joyce G. The Origins of the RNA World. Cold Spring Harbor Perspectives in Biology [Internet]. 2010 [cited 3 December 2017];4(5):1-12. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3331698/</ref> Although it is widely accepted that RNA preceded DNA their is also a pre-RNA world theory in which simpler biomolecules would, through evolution, become what eventually became RNA. <ref>Klyce B. The RNA World and other origin-of-life theories. by Brig Klyce [Internet]. Panspermia.org. 2017 [cited 3 December 2017]. Available from: http://www.panspermia.org/rnaworld.htm</ref>

=== References ===

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Relay neuron

2017-12-03T13:15:54Z

160446287: Added information and extra reference

A relay [[Neuron|neuron]] (also known as an interneuron) passes signals between [[Neurons|neurons]].  Relay neurones are only found in the brain, visual system and [[Spinal cord|spinal cord]] acting to relay signals. They recieve a signal from one neuron and then transfer the signal to another interneuron resulting in the signal being passed to a [[Motor neuron|motor neurone]] thus driving the reaction to the [[Stimulus|stimulus. ]] <ref>Becker W., Hardin J., Bertoni G., and Kleinsmith L. (2012) Becker’s World Of The Cell, 8th Edition, San Francisco: Pearson Education. Page 365</ref> These can be differentiated from other neurones by observing their short [[Dendrites|dendrites]] and either long or short axons..<ref>The structure and function of sensory, relay and motor neurons. [Internet]. Psychology Hub. 2017 [cited 3 December 2017]. Available from: https://psychologyhub.co.uk/the-structure-and-function-of-sensory-relay-and-motor-neurons/</ref>

=== References ===

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Vena cavae

2017-11-19T12:35:23Z

160446287: Basic function and positioning of Vena Cavae

'''''Vena Cavae '''''consist of the two largest veins within the human body and are divided into two separate [[Blood vessels|blood vessels]], the superior vena cava and the inferior vena cava. 


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'''''The superior vena cava (SVC), '''''is a large valveless venous channel formed by the union of the brachiocephalic veins. It receives blood from the upper half of the body (except the heart) and returns it to the right atrium. [1] '''''The inferior vena cava (IVC)'''''''', '''also empties into the right atrium of the heart and .  The inferior vena cava runs posterior, or behind, the abdominal cavity. This vein also runs alongside the right vertebral column of the spine and unlike the SVC contains a valve. [2] These blood vessels enable the return of depleted deoxygenated blood from all parts of the body to the heart to be pumped to the lungs for reoxygenation via the pulmonary arteries. ''' '''

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[1] - Bashir, O. (2017). Superior vena cava | Radiology Reference Article | Radiopaedia.org. [online] Radiopaedia.org. Available at: https://radiopaedia.org/articles/superior-vena-cava [Accessed 19 Nov. 2017].

[2] - Healthline Medical Team, (2015). Inferior Vena Cava Function, Anatomy & Definition | Body Maps. [online] Healthline.com. Available at: https://www.healthline.com/human-body-maps/inferior-vena-cava [Accessed 19 Nov. 2017].

Vena cavae

2017-11-19T12:34:23Z

160446287: Basic function and positioning of Vena Cavae

'''''Vena Cavae''''''''''The superior vena cava (SVC),''''' '''''The inferior vena cava (IVC)'', also empties into the right atrium of the heart and .  The inferior vena cava runs posterior, or behind, the abdominal cavity. This vein also runs alongside the right vertebral column of the spine and unlike the SVC contains a valve. [2] These blood vessels enable the return of depleted deoxygenated blood from all parts of the body to the heart to be pumped to the lungs for reoxygenation via the pulmonary arteries.  

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[1] - Bashir, O. (2017). Superior vena cava | Radiology Reference Article | Radiopaedia.org. [online] Radiopaedia.org. Available at: https://radiopaedia.org/articles/superior-vena-cava [Accessed 19 Nov. 2017].

[2] - Healthline Medical Team, (2015). Inferior Vena Cava Function, Anatomy & Definition | Body Maps. [online] Healthline.com. Available at: https://www.healthline.com/human-body-maps/inferior-vena-cava [Accessed 19 Nov. 2017].