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Plasmid

2018-01-15T17:49:10Z

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Plasmids are [[Supercoiled|supercoiled]] [[DNA|DNA]] molecules present in most species of [[Bacteria|bacteria]]. These are not integrated into the host [[Chromosome|chromosome]] and are much smaller in length.

Plasmids are not necessary for the survival of a [[Bacteria|bacteria]] but can contain [[Gene|genes]] that are advantageous in changing environmental conditions, an example would be [[Antibiotic resistance|antibiotic resistance]] [[Gene|genes]] <ref>Maloy (1987), Microbial Genetics, 2nd edition, Jones and Bartlett Publishers.</ref>.

Plasmids have no replication machinery of their own and are reliant upon the host for duplication.

Plasmids are very useful as vectors and in [[Recombinant DNA Technology|recombinant DNA techniques]]. Desired [[Genes|genes]] can be inserted in and amplified up.

Examples of plasmids include the [[puC18|puC18]], or the F plasmid. Note that the [[F_plasmid|F plasmids]] are unusually large. This property allows large scale genetic exchange between bacteria. 

=== Plasmid Conformation ===

[[Plasmids|Plasmids]] exist in three forms: Open circle, supercoiled and linear. Supercoiled is when the plasmid has is tightly wound round itself in order to fit inside the cell. Open circle is when there is a nick in the outer ring of the plasmid and linear is when the plasmid is cut with a [[Restriction enzyme|restriction enzyme]]. Concatamers also form which is where there are several repeats of plasmid DNA produced and not snipped. This forms one long chain of DNA which runs very slowly down the agarose gel. <ref>Biological Sciences - Microbiology:
Ronen Borenstein and Niza Frenkel
Cloning human herpes virus 6A genome into bacterial artificial chromosomes and study of DNA replication intermediates
PNAS 2009 106 (45) 19138-19143; published ahead of print October 26, 2009, doi:10.1073/pnas.090850410http://www.pnas.org/content/106/45/19138.full</ref>

When run on an agarose gel, supercoiled runs the fastest down the gel, then linear then open cirlce. 

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Ventricles

2017-10-16T16:17:57Z

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The primary role of ventricles is the forcible pumping of blood around the cardiovascular system, to provide the necessary resources to the tissues of the body.

There are two ventricles which form the lower chambers of the left and right hand sides of the [[Heart|Heart]]. They are larger than the upper chambers, called the [[Atria|atria]]. The ventricles provide the high [[Blood_pressure|blood pressure]] needed to circulate blood around the entire [[Cardiovascular_system|cardiovascular system]] due to their high muscle density, with the left ventricle having larger walls and thus more muscle. This is necessary due to the fact that it pumps blood around the body, as opposed to the right ventricle which only pumps to the [[Lungs|lungs]].

When in [[systole|systole]], the muscles of the ventricles contract, increasing the internal pressure of the ventricle and thus forcing blood out through the [[aorta|aorta]] and the [[aortic valve|aortic valve]] (in the case of the left hand ventricle), and into circulation. The right hand ventricle works identically, however instead of supplying systemic circulation with blood, it instead supplies the [[pulmonary artery|pulmonary artery]] (and then lungs) through the pulmonary valve.

In [[diastole|diastole]] the ventricles relax, so the pressure within the ventricles is lower than that of the atria, thus allowing the blood in the atria to flow through into the ventricles through the tricuspid (right ventricle) and mitral (left ventricle) valves.

Respiratory tract

2016-12-01T15:11:07Z

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The Repiratory Tract is an essential collection of organs that allow for the absorption of Oxygen into the blood and the removal of CO2 from it. It allows for the ventilation of atmospheric air into the lungs, where gas exchange occurs, and the removal of waste gases that diffuse from the blood to be released into the atmosphere. This is essential for complex life as Oxygen is used in [[Oxidative_phosphorylation|oxidative phosphorylation]], which produces [[ATP|ATP]] from [[Pyruvate|pyruvate]]. ATP is essential in many processes in the body - e.g. [[Muscle_contraction|Muscle Contraction]], [[Active_Transport|Active transport]]. 

The Respiratory Tract is lined with [[Epithelium|epithelium]] which move the mucus up towards the mouth in a sweeping motion. Once the [[Mucus|mucus]] has reached the mouth it is swallowed via the [[Oesophagus|oesophagus]].

'''Structure'''

The respiratory tract is segmented into two main sections, the Upper Respiratory tract and the lower. The upper is made of the nasal cavity which flows through to the pharynx, then the larynx, followed by the lower respiratory tract whch comprises of the [[trachea|trachea ]]which divides into the [[Bronchi|bronchi]], the [[Bronchioles|bronchioles]] and finally the [[Alveoli|alveoli]]. These act as a tree like structure of branching and increasingly complex and intricate structures<ref>Inner Body. Respiratory System. Cited 1/12/2016. Available from: http://www.innerbody.com/anatomy/respiratory</ref>. The increasing concentration of smaller and smaller structures leads eventually in the alveoli to a very large surface area where [[Diffusion|diffusion]] is optimised, and gas exchange can occur quickly.  

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