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Peptidoglycan

2018-10-17T16:19:34Z

170048930: corrected spelling

Peptidoglycan is found in both [[Gram-negative|Gram-negative]] and [[Gram-positive|Gram-positive]] [[Bacteria|bacteria]]. It is present in larger amounts in Gram-positive bacteria as it appears as a multimolecular layer and can be found in association with additional compounds. In Gram-negative bacteria, it is found in either 1 or 2 layers between the inner and outer membrane<ref>http://www.chem.qmul.ac.uk/iupac/misc/glycp.html#3.9</ref>. 

Peptidoglycan is a [[Macromolecule|macromolecule]] made up of alternating [[Residues|residues]] of [[N-acetyl-β-D-glucosamine|N-acetyl-β-D-glucosamine]] (NAG) and [[N-acetylmuramic acid|N-acetylmuramic acid]] (NAM) joined together by a [[Glycosidic bond|glycosidic bond]]<ref>http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/prostruct/cw.html</ref>. There is then a [[Pentapeptide|pentapeptide]] attached to the NAM amino acid which forms cross-links with other polysaccharide chains forming a 3D mesh-like layer. These cross-links are formed using the enzyme [[Glycopeptide transpeptidase|glycopeptide transpeptidase]] and provide peptidoglycan with stability. This stability allows it to provide mechanical support and prevent osmotic lysis from occurring in bacteria<ref>Berg J., Tymoczko J and Stryer L. (2012) Biochemistry, 7th edition, New York: WH Freeman: pg 252</ref>.

[[Penicillin|Penicillin]] [[Inhibits|inhibits]] the effect of peptidoglycan in bacteria by binding to [[Serine|serine]] in the enzyme [[Glycopeptide transpeptidase|glycopeptide transpeptidase]]. As a result, it can no longer catalyse the formation of cross-links. The enzyme is irreversibly inhibited which therefore results in the termination of bacterial growth<ref>http://www.ncbi.nlm.nih.gov/books/NBK7986/</ref>.

Penicillin inhibits the transpeptidase linking together the polysaccharide chains and cells become osmotically sensitive and burst.

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Peptidoglycan

2018-10-17T16:17:47Z

170048930: corrected 2 spelling errors

Peptidoglycan is found in both <a href="Gram-negative">Gram-negative</a> and <a href="Gram-positive">Gram-positive</a> <a href="Bacteria">bacteria</a>. It is present in larger amounts in Gram-positive bacteria as it appears as a multimolecular layer and can be found in association with additional compounds. In Gram-negative bacteria, it is found in either 1 or 2 layers between the inner and outer membrane<ref>http://www.chem.qmul.ac.uk/iupac/misc/glycp.html#3.9</ref>. 

Peptidoglycan is a <a href="Macromolecule">macromolecule</a> made up of alternating <a href="Residues">residues</a> of <a href="N-acetyl-β-D-glucosamine">N-acetyl-β-D-glucosamine</a> (NAG) and <a href="N-acetylmuramic acid">N-acetylmuramic acid</a> (NAM) joined together by a <a href="Glycosidic bond">glycosidic bond</a><ref>http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/prostruct/cw.html</ref>. There is then a <a href="Pentapeptide">pentapeptide</a> attached to the NAM amino acid which forms cross-links with other polysaccharide chains forming a 3D mesh-like layer. These cross-links are formed using the enzyme <a href="Glycopeptide transpeptidase">glycopeptide transpeptidase</a> and provide peptidoglycan with stability. This stability allows it to provide mechanical support and prevent osmotic lysis from occurring in bacteria<ref>Berg J., Tymoczko J and Stryer L. (2012) Biochemistry, 7th edition, New York: WH Freeman: pg 252</ref>.

<a href="Penicillin">Penicillin</a> <a href="Inhibits">inhibits</a> the effect of peptidoglycan in bacteria by binding to <a href="Serine">serine</a> in the enzyme <a href="Glycopeptide transpeptidase">glycopeptide transpeptidase</a>. As a result, it can no longer catalyse the formation of cross-links. The enzyme is irreversibly inhibited which therefore results in the termination of bacterial growth<ref>http://www.ncbi.nlm.nih.gov/books/NBK7986/</ref>.

Penicillin inhibits the transpeptidase linking together the polysaccharide chains and cells become osmotically sensitive and burst.

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Insulin resistance

2017-12-06T11:11:05Z

170048930: cleaned up text

[[Insulin|Insulin]] resistance is a condition were [[Cells|cells]] can't respond normally to [[Insulin|insulin]], so the [[Blood|blood]] [[Sugar|sugar]] levels rise<ref>1. Wikipediaorg. [Online]. Available from: https://en.wikipedia.org/wiki/Insulin_resistance [Accessed 5 December 2016].</ref>.  

Insulin resistance is also the main pathology of [[Type 2 diabetes|Type 2 Diabetes]]<ref name="[2]">Chiu, H., Tsai, E., Juneja, R., Stoever, J., Brooks-Worrell, B., Goel, A., &amp;amp;amp; Palmer, J. (2007). Equivalent insulin resistance in latent autoimmune diabetes in adults (LADA) and type 2 diabetic patients. Diabetes Research And Clinical Practice, 77(2), 237-244. http://dx.doi.org/10.1016/j.diabres.2006.12.013</ref>.

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Atom

2017-12-06T11:08:24Z

170048930: cleaned up text

The atom is defined as the smallest subdivision of an [[Element|element]].  Atoms of the same [[Element|element]] have the same size, mass and chemical properties<ref>http://js082.k12.sd.us/My_Classes/Physical_Science/atoms/atoms_1.htm</ref>. 

An atom is composed of three different particles: [[Protons|protons]] (p+), [[Neutrons|neutrons]] (n0) and [[Electrons|electrons]] (e-) .

[[Protons|Protons]] and [[Neutrons|neutrons]] are located in the [[Nucleus|nucleus]] of the atom, whereas the [[Electrons|electrons]] spin around this [[Nucleus|nucleus]] in specific orbits<ref>http://js082.k12.sd.us/My_Classes/Physical_Science/atoms/atoms_1.htm</ref><ref>http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookCHEM1.html</ref>.

The addition of the number of [[Protons|protons]] and [[Neutrons|neutrons]] produces the [[Atomic mass|atomic mass]] of an element, whereas the number of [[Protons|protons]] equals with the number of the [[Electrons|electrons]] of the same element and are equal with the [[Atomic number|atomic number]] of this [[Element|element]]<ref>http://www.clickandlearn.org/Gr9_Sci/atoms/modelsoftheatom.html</ref>. The number of neutrons can vary significantly especially in [[Radioactive|radioactive]] elements. The number of neutrons in the atom defines the isotope of the element<ref>^ Leigh, G. J., ed. (1990). International Union of Pure and Applied Chemistry, Commission on the Nomenclature of Inorganic Chemistry, Nomenclature of Organic Chemistry – Recommendations 1990. Oxford: Blackwell Scientific Publications. p. 35. ISBN 0-08-022369-9. "An atom is the smallest unit quantity of an element that is capable of existence whether alone or in chemical combination with other atoms of the same or other elements."</ref>.

How the atom is really structured was a serious matter for many centuries and different theories raised from [[Democritus|Democritus]] (c.300 BC), [[Dalton|Dalton]] (c.1800), [[J.J. Thomson|J.J. Thomson]] (c.1850), [[Rutherford|Rutherford]] (c. 1905), [[Neils Bohr|Neils Bohr]], Bohr-Rutherford (c. 1920) to “Modern theory” which describes the orbits of the spinning [[Electrons|electrons]] around the [[Nucleus|nucleus]] as a "cloud of energy levels"<ref>http://www.clickandlearn.org/Gr9_Sci/atoms/modelsoftheatom.html</ref><ref>http://www.clickandlearn.org/chemistry/atomic_theory.htm</ref>.

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Bronchi

2017-11-26T14:25:39Z

170048930: Cleaned up the text.

The bronchi tree is a constituent of the trachea. The trachea divides into two main bronchi: one for the left [[Lung|lung]] and the other for the right lung. The right bronchus is larger than the left bronchus. The bronchi tree forms a more branched tracheobronchial tree.

The primary bronchus then divides into a secondary lobar bronchi. This has three branches on the right and two branches on left. The secondary bronchi then further divides into tertiary bronchi that "supply the bronchopulmonary segments". After the tertiary bronchi, there is a conducting bronchiole and then terminal bronchioles<ref>Keith L. Moore, Arthur F. Dalley, Anne M. R. Agur, (2010), Clinically Oriented Anatomy, 6th Edition: Page 112-115, Philadelphia, Lippincott Williams &amp; Wilkins, a Wolters Kluwer business.</ref>.

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Exocytosis

2017-11-26T14:18:55Z

170048930: Cleaned up the text.

Exocytosis is a vesicular pathway that involves finalised and [[Secretory vesicles|secretory vesicles]] leaving the [[Golgi apparatus|Golgi apparatus]]. It is the functional opposite of [[Endocytosis|endocytosis]]. Exocytosis is an outward pathway, beginning from the [[Endoplasmic reticulum|endoplasmic reticulum]] (ER). Once [[Proteins|proteins]] have been modified and sorted in the [[Endoplasmic reticulum|ER]] and Golgi apparatus, they are stored in membrane bound vesicles, which are then transported to the plasma membrane or organelles ( such as [[Lysosome|lysosomes]]/[[Endosome|endosomes]]) depending upon function. This entire pathway is the outward pathway.

Vesicles exit from the trans face of the [[Golgi apparatus|Golgi apparatus]], or the "late" face, and head towards the [[Plasma membrane|plasma membrane]] via one of a further two secretory pathways: constitutive or regulatory <ref>Alberts, B et al (2008). Molecular biology of the cell. 5th edition. US Garland Science. Page 800</ref>.

In the constitutive phase, this pathway occurs in all cell types. The constitutive pathway directs vesicles either towards [[Endosome|endosomes]]/[[Lysosome|lysosomes]] or immediately directs them towards the [[Plasma membrane|plasma membrane]]. It involves modified [[Lipid|lipids]] and [[Proteins|proteins]] in vesicles which head towards and fuse with the [[Plasma membrane|plasma membrane]], after "budding off" from the trans face of the [[Golgi apparatus|Golgi apparatus]]. The vesicle reaches a specific location on the membrane via the use of docking [https://teaching.ncl.ac.uk/bms/wiki/index.php/SNARE SNARE proteins]. These proteins on the vesicle and membrane bind together to form a SNARE complex so the vesicle is in the right location on the membrane and also to catalyse the reaction for fusion to occur.<ref>Pfeffer SR (2007); “Unsolved Mysteries in Membrane Traffic” Annual Review of Biochemistry 76:629-645</ref> Once successful fusion is accomplished the contents of the [[Vesicle|vesicle]] are secreted into the extracellular environment, the [[Lipid|lipids]] and proteins in these vesicles become components for the membrane whilst other [[Proteins|proteins]] are released into the extracellular environment. Contents destined for [[Lysosome|lysosomes]] are usually contained in specific departing vesicles, for example in which a compound [[Mannose-6-phosphate|M6P]] ([[Mannose-6-phosphate|mannose-6-phosphate]]) allows fusion with the [[Endosome|endosomes]], whereas other vesicles do not have this compound attached <ref>Alberts, B et al (2008). Molecular biology of the cell. 5th edition. US Garland Science. Page 800</ref>.

Regulated pathways are more common in secretory cells such as [[White blood cells|white blood cells]] and [[Epithelial cells|epithelial cells;]] cells that must rapidly produce products such as [[Hormone|hormones]] and specialised [[Enzyme|enzymes]] <ref>Alberts, B et al (2008). Molecular biology of the cell. 5th edition. US Garland Science. Page 800</ref>. Vesicles containing secretory [[Proteins|proteins]] are only able to fuse with the membrane under controlled conditions. These vesicles do not fuse with the [[Plasma membrane|plasma membrane]] once they arrive there, unlike the constitutive pathway; they are carried by microtubules on the cells' [[Cytoskeleton|cytoskeleton]] to near the surface of the membrane. The vesicles only fuse with the membrane once they receive a signal from a receptor after a messenger (e.g. a [[Hormone|hormone]]) has successfully bonded to the receptor. This complex activates intracellular signals that cause the vesicles to fuse with the membrane and release their contents into the environment. A good example is in [[Nerve cell|nerve cells]] in the pre-synaptic membrane, when an action potential reaches the pre-synaptic membrane and causes a flow of [[Calcium|calcium]] [[Ion|ions]] into the cell, these ions then allow the vesicles to fuse with the membrane and release their contents; in the case with neurons it is usually [[Neurotransmitter|neurotransmitters]] such as [[Acetylcholine|acetylcholine]] and [[Dopamine|dopamine]] released <ref>Alberts, B et al (2008). Molecular biology of the cell. 5th edition. US Garland Science. Page 804</ref>.

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Peptidase

2017-11-26T14:08:26Z

170048930: Cleaned up the text.

Peptidase is also known as [[Protease|protease]] or proteinase. They are produced in the [[Stomach|stomach]], [[Small intestine|small intestine]] and [[Pancreas|pancreas]] <ref>http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/enzymes/enzymes_and_digestion2.shtml</ref> and are responsible for the cleavage of [[Peptide bond|peptide bonds]] between [[Amino acid|amino acids]] via [[Hydrolysis|hydrolysis]] reactions, as shown in figure 1.

[[Image:Hydrolysis Reaction.gif|Figure 1: A diagram to showing the hydrolysis of a peptide bond]]<ref>http://www.wiley.com/college/pratt/0471393878/student/review/kinetics/5_catalysts.html</ref>

Thus, they have roles in the breakdown of proteins within the body. For example, peptidases in the digestive tract break down proteins entering the body from our food, thereby releasing their constituent amino acids allowing them to be used in different processes.<ref>http://www.wisegeek.org/what-is-peptidase.htm</ref>

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Leptin

2017-11-17T17:47:37Z

170048930: corrected grammar, spelling and referencing.

Leptin is a cytokine protein [[Hormone|hormone]] produced by the body's [[Adipose tissue|adipose]] cells. leptin comes from the Greek word “leptos” for thin<ref name="null2">Theodore Kelesidis, M.D.,* Iosif Kelesidis, M.D.,* Sharon Chou, M.D.,* and Christos S. Mantzoros, M.D., D.Sc. The role of Leptin in human physiology: emerging clinical applications Ann Intern Med. 2010; 150(2) 93-103</ref>. Leptin provides a vital role in regulating energy balance<ref name="null">Klok MD1, Jakobsdottir S, Drent ML.The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. 2007 Jan. Available from: https://www.ncbi.nlm.nih.gov/pubmed/17212793</ref>. The concentration of leptin found is dependent on the total amount of body fat, thus it differs between individuals. It works by inhibiting hunger by sending signals to the [[Hypothalamus|hypothalamus]]<ref>Hormone Health Network. What does Leptin do? 2016. Available from: http://www.hormone.org/hormones-and-health/what-do-hormones-do/cortisol/leptin</ref>

The hormone was discovered through experimental research on obese mice by chance in Jackson laboratories<ref name="null2" />. The research produced data indicating that mice with homozygous mutation of the leptin gene and thus leptin deficiency, developed extreme obesity, diabetes, neuroendocrine abnormalities and infertility<ref name="null2" />.

Leptin is thought to be required for energy homeostasis by targeting LEPRb- expressing neurones in the brain, but more specifically the hypothalamus<ref>Yingjiang Zhou and Liangyou Rui. Leptin signalling and Leptin Resistance. Front Med. 2013 Jun; 7(2): 207–222.</ref>. The immediate effects of the release of leptin include the regulation of appetite by binding to specific receptors that induce complex neural circuits that activate either anorexigenic (appetite suppressing) or orexigenic (appetite stimulating) neuropeptides to control food intake<ref name="null2" />.

Leptin is a 16kDA adipose-derived [[Cytokine|cytokine protein]] which consists of 167 [[Amino acid|amino acids]]. This protein is coded by the ob gene on [[Chromosome|chromosome ]]7.

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Lipolysis

2017-11-17T17:33:08Z

170048930: corrected grammar.

Lipolysis is the [[Catabolism|catabolism]] of triacylglycerols (TAG) which are stored in the form of [[Lipid|lipids]]. It involves [[Hydrolysis|hydrolysis]] of [[Triglycerides|triglycerides]] into [[Glycerol|glycerol]] and [[Fatty acids|fatty acids]]. It's an important part of [[Homeostasis|homeostasis]] and occurs in most [[Tissue|tissues]]<ref name="nullLipolysis – A highly regulated multi-enzyme complex mediates the catabolism of cellular fat stores">Prog Lipid Res. 2011 Jan; 50(1-4): 14–27. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3031774/)</ref>. 

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Body mass index

2017-11-17T17:30:53Z

170048930: corrected spelling and grammar.

Body mass index (BMI) is used as an indicator of general health. It is calculated taking into account a person's height and weight.

The calculation is:  BMI = Weight (kg) / Height2 (m)

This calculation categorises people into distinct groups:

*If a person's BMI is less than 18.5 kg/m2 then that person is considered 'underweight'.
*If a person's BMI is between 18.5 kg/m2 and 24.9 kg/m2 then that person is considered 'healthy'.
*If a person's BMI is equal to or above 25 kg/m2 then that person is considered 'overweight'.
*If a person's BMI is equal to or above 35 kg/m2 then that person is considered '[[Obese|obese]]'.
*If a person's BMI is equal to or above 40 kg/m2 then that person is considered 'morbidly obese'.

Height-weight tables are used to display this information in a clear manner. 

However, calculating a person's BMI is not always the best method of calculating how healthy that person may be. For example, athletes may have higher body mass indices but have a very low body fat. Men are also likely to have a higher body mass index than women of the same height. It is only by considering body composition as a whole that we can get an ideal picture of how healthy or not a person may be. This includes looking at height, weight, gender, age, [[Body fat percentage|body fat percentage]], frame size and energy expenditure.<ref>Gropper, S.S., Smith, J., &amp;amp; Groff, J., 2005. 'Advanced Nutrition and Human Metabolism,' Wadsworth/Thomson. (pp. 519-530).</ref> 

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Ion channel

2017-11-17T17:25:36Z

170048930: corrected spelling mistakes and grammar.

Ion channels are [[Hydrophllic|hydrophilic]] pores in a plasma membrane, they are gated which means they are only open when stimulated for example by voltage. The channels are also selective, allowing only some [[Ions|ions]] to pass; for example [[Sodium|sodium]] or [[Potassium|potassium]]<ref>Alberts,Molecular Biology of the cell 5th editon,2008,page 668</ref><ref>Alberts,Molecular Biology of the cell 5th editon,2008,page 668</ref>. Ion channels can be classed into three main families: [[Voltage-gated ion channels|voltage gated ion channels]], [[Ligand gated ion channels|ligand gated ion channels]] and [[Mechanically gated ion channles|mechanically gated ion channles]]<ref>Lyons. I (2011). Biomedical Science Lecture Notes. Oxford: Wiley-Blackwell. 82.</ref>.

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Genetic mutation

2017-11-17T17:08:29Z

170048930: I added spacing and also corrected a grammatical error so the sentence might make more sense.

'''Genetic mutation- '''this term indicates an alteration to base sequence in [[DNA|DNA]] of an organism which results in a mutant [[Allele|allele]] of a [[Gene|gene]] i.e. an allele that occurs in less than 1% of population. The change is heritable and can be passed on to offspring if fixed into the parental [[Genome|genome]]. Mutations can vary depending on the type of genomic alteration:

*addition
*deletion
*substitution
*rearrangement of bases.

To investigate the events leading to mutation we can look at the 3 types of mutagenesis process:

*spontaneous (no mutation causing agent)
*induced (a foreign genome introduced e.g.in the laboratory)
*directed (in vitro change to genome). 

We can calculate the rate of mutation occurance using an equation from Poisson distribution:

'''P0=e-mN''' 

where P0 is the probability of seeing no mutations, N is the number of cells per culture and m is the mutation rate <ref>Genetics, 1987, Geoffrey Zubay</ref><ref>Encyclopedia of Genetics,Volume 3, 2002, S.Brenner,J.H. Miller</ref>. 

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