Tuberculosis. Primary and post-primary infection and pulmonary tuberculosis. The most common causative agent, Mycobacterium Tuberculosis, was discovered in 1882 by the German microbiologist Robert Koch.1 It is a slow growing Gram positive rod with a very
Tuberculosis Tuberculosis is a bacterial disease. The most common causative agent, Mycobacterium Tuberculosis, was discovered in 1882 by the German microbiologist Robert Koch.1 It is a slow growing Gram positive rod with a very thick waxy capsule. It has since been discovered that the disease can also be caused by several other Mycobacteria. In America Tuberculosis was thought to have been prevented from being a public health problem. However in the early 1990's TB re-emerged, particularly in the inner city areas and in places where HIV infection levels were high.2 The most common form of TB is pulmonary tuberculosis, an infection of the lungs, however the bacterium is capable of spreading to virtually any other organ. Primary and post-primary infection and pulmonary tuberculosis Primary infection is the term used when a host is initially infected. This is usually caused by droplets in the air containing viable Mycobacteria being inhaled, or by inhalation of infected dust particles. The bacteria will settle in the lungs and the most common form of TB, pulmonary Tuberculosis, will occur. The bacteria are engulfed by alveolar macrophages where they can survive and multiply. Non resident macrophages are attracted to the site where they also engulf the bacteria and carry them to the local lymph nodes where an immune response is activated. 2-6 weeks after this
Describe the Concept and Discuss the Importance of Homeostasis
Describe the Concept and Discuss the Importance of Homeostasis Homeostasis occurs to some extent in all living organisms. All organisms need some control on their internal environmental conditions in order to ensure that they will be able to survive. Since many of the metabolic reactions that occur within an organism depend on the use of enzymes or even the use of other organisms such as prokaryotic bacteria, it is essential that the optimal conditions required for the functioning of that enzyme be provided. Homeostasis therefore, is 'the tendency of organisms to regulate and maintain relative internal stability', and involves, among other processes, the maintenance of a constant body temperature, glucose concentration, pH, osmotic pressure, oxygen level, and ion concentrations. The ability to maintain a constant internal environment, with which we are most familiar, is that of a constant body temperature in homeothermic organisms. For example, the average body temperature of a human is 36.6°C, and varies not more than 0.5 of a degree in healthy humans. However, Poikilotherms are animals whose body temperature fluctuates with the ambient temperature, and thus have no biochemical method of temperature maintenance. Since control is needed however, Poikilotherms, such as chameleons, have developed adaptive methods for coping with this problem. They often bask in the sun
This review looks at how silicification of bacteria allows preservation of the bacteria through fossilisation and also helps the bacteria to survive the hostile environment.
Essay - News and Views Environmental Microbiology & Bioresources The living condition in early Earth is very different from the modern world. Some bacteria found ways to survive through various strategies. This review looks at how silicification of bacteria allows preservation of the bacteria through fossilisation and also helps the bacteria to survive the hostile environment. The habitable environment of early Earth is very different from what it is today. The early earth was significantly hotter, [1, 2] and the oxygen level was extremely low with less than 0.2% than that of present atmospheric levels. [3, 4] The early Earth was also strongly influenced by strong hydrothermally activity, leading to sea-water temperature to hit as high as 55oC. [5] Such hydrothermal influence can result in massive silicification of both sedimentary and volcanic units in early Archean terrains found in many regions such as Barberton greenstone belt in South Africa [6] and Pilbara Craton in northwest Australia. [7, 8] With such high concentration of silica, micro-organisms may be preserved in a fossil as silicified remnants. [9] The study of microbial silicification is important as they can provide information of microbe-silica interactions in places such as hot springs. Moreover, modern geothermal technology allow for contemporary analogues for conditions which Precambrian microorganisms
The theory behind this experiment is that of rate laws and rate expressions. Arsenious acid, the reducing agent present in this experiment, reacts with iodine at the rate it is formed.
Introduction The theory behind this experiment is that of rate laws and rate expressions. Arsenious acid, the reducing agent present in this experiment, reacts with iodine at the rate it is formed. Therefore, by measuring the time it takes for the consumption of arsenious acid to occur, one can determine the rate of iodine formation. This would be considered the rate-controlling step. The rate-controlling step of the reaction is the step that proceeds so much more slowly than all the others that it effectively controls the overall reaction rate. The order of a reaction is determined by the reaction mechanism, which is also related and equal to the number of reactant molecules in the rate-controlling step of the reaction. In the initial-rate method, the reaction is run only long enough to determine an initial rate. The reaction being considered is : IO3- + 8I- + 6H+ ? 3I3- + 3H2O ( Equation 1) The rate law associated with this reaction can be written as: d [IO3-] =ƒ([IO3-],[I-],[H+],[I3-],[H2O]......) dt (Equation 2) however the most frequently type of rate law for this reaction is of the form; d [IO3-] =k([IO3-] m,[I-]n,[H+}p,.) dt (Equation 3) where m, n, p,... are determined by experiment, and each exponent in the equation is the order of the reaction with respect to the corresponding species, and
Searle's solution to the mind-body problem.
Tram Nguyen SID 14732604 October 24 2002 Philosophy 132 Professor J. Searle GSI Ben Callard Searle's solution to the mind-body problem (#1) Searle's solution to the mind-body problem is Biological Naturalism (BN), a doctrine that consists in two theses: ) Brains cause minds. 2) Mental states are features of brains. To understand these two theses, Searle proposes that we first emancipate ourselves from the vocabulary of the old Cartesian, dualistic world-view in which mind and matter are two separate entities, and that furthermore, the mental and the physical are two separate spheres. Rejecting such a Cartesian vocabulary would then allow us to see the consistency of the two theses in respect to each other, as well as in respect to the current "scientific" world-view. Since Searle argues for his two theses by appealing to this scientific world-view to, this view should be briefly explained here. For Searle, the "scientific" world-view comprises of two main theories: atomic theory and biological evolution. Atomic theory asserts that the universe is made up off tiny particles; biological evolution asserts that the universe is the way it is because of selective changes that have been occurring ever since the beginning of the universe. Let us keep these two notes in mind (one, rejection of Cartesian vocabulary, and two, scientific world-view) as we consider the two
Separations in paper chromatography involve the same principles as those in thin layer chromatography.
Separations in paper chromatography involve the same principles as those in thin layer chromatography. In paper chromatography, like thin layer chromatography, substances are distributed between a stationary phase and a mobile phase. The stationary phase is usually a piece of high quality filter paper. The mobile phase is a developing solution that travels up the stationary phase, carrying the samples with it. Components of the sample will separate on the stationary phase according to how strongly they adsorb to the stationary phase versus how much they dissolve in the mobile phase. In all types of chromatography, the sample is placed on one end of a tube or plate which contains an inert material called a stationary phase, and a solvent, called the mobile phase, flows over it. The fundamental principle of chromatography is the equilibrium that forms when a compound is either dissolved in a mobile phase or absorbed on a stationary phase. The chamber should be saturated with the developing solvent to achieve high resolution. Discussion: When the leaves of green plants are extracted, a complex mixture of components is obtained. The components that are obtained include anthocyanin, chlorophyll a and b, carotenes, and xanthophylls. If you try to extract these components from the green leaves by using water, the extraction is rather ineffective. This is because water is a polar
How had research over the past 25 years led us to think that microbes may be able to survive in extraterrestrial environments?
Our current understanding of life in extreme environments strongly suggests that if life exists elsewhere in the solar system it is highly likely to be microbial. How has research over the past 25 years led us to think that microbes may be able to survive in such extraterrestrial environments? The idea of extraterrestrial life is not novel. Over 2,000 years ago, a Greek philosopher wrote, "It is unnatural in a large field to have only one shaft of wheat, and in the infinite Universe only one living world" (Papagiannis 1984). Enthusiasm concerning life elsewhere in the solar system continued towards the late 20th century (Brake 2006), until these ancient old notions were dashed when robotic space explorations revealed inhospitable planets (Klein 1999). Nonetheless, more recently, discoveries closer to home revived interest in the possibility of extraterrestrial life. Over the last few decades, not only have many environmental extremes on Earth been uncovered, but organisms have been found thriving in these conditions (Rothschild & Mancinelli 2001). These organisms were named extremophiles ('lovers of extreme' Malceroy 1974). The term 'extreme' is difficult to define since it is dependent on the organism; 'extreme' for one organism might be the norm, or even essential, to the survival of another. However, a scientifically viable definition of 'extreme' that will be used
"So many peptides, so few grooves" - compare the ways in which specific antigen recognition is accomplished by MHC molecues, by T cell receptors and by antibody molecules.
T. Konrad Rajab The Queen's College University of Oxford "So many peptides, so few grooves" - compare the ways in which specific antigen recognition is accomplished by MHC molecues, by T cell receptors and by antibody molecules Introduction Specific antigen recognition lies at the heart of the adaptive immune response. This essay will compare how MHC, TCR and Ab molecules accomplish this feat. Structural differences in antigen-binding site Thanks to X-ray crystallography, we have a rather clear picture of the structure of the antigen-binding sites of the three relevant proteins. In the case of the MHC, the peptide-binding groove consists of a floor and two walls. Importantly, this structure is germline-encoded. In the floor, the ? chain of the class I molecule or the ? and ß chains of the class II molecule form a ß-pleated sheet. The walls are constituted by ?-helixes. In the MHC class I molecule, walls and floor are formed by the ? chain. Also, ?1 and ?2 domains of this chain converge such that they close the class I peptide-binding groove. This is not the case in MHC class II molecules. As a result, class I molecules can accommodate peptides that are 8 to 11 residues long whereas class II molecules optimally bind peptides with a length of 12 to 16 residues. One way in which the molecular interaction between peptide and MHC has been studied is by introducing
Permanent and Temporary Dipoles
Permanent and Temporary Dipoles Dipoles: * A molecule with a positive end and a negative end * When a molecule has a dipole it is called polarised * There are several ways a molecule can become polarised Permanent Dipoles: * Permanent dipoles occur when a molecule has two atoms bonded together which have substantially different electro negatively, so that one atom attracts the shared electrons much more than the other * Hydrogen chloride has a permanent dipole, because chlorine is much more electronegative than hydrogen, and so attracts the shared electrons more * Molecules with a permanent dipole are called polar molecules Instantaneous Dipoles: * Some molecules do not possess a permanent dipole, because the atoms that are bonded together have the same, or very similar, electro negatively, so that the electrons are evenly shared * Even though the molecule doesn't have a permanent dipole, a temporary, or instantaneous dipole can arise * Left on its own, this dipole only lasts for an instant before the swirling electron cloud changes its position, cancelling pout or even reversing the dipole * However, if there are other molecules nearby, the instantaneous dipole may affect them and produce induced dipoles Induces Dipoles: * If an unpolarised molecule finds itself next to a dipole, the unpolarised molecule may get a dipole induced in it * The dipole attracts or
A pathophysiology review on emphysema
A Pathophysiology Review on Emphysema Abstract: Emphysema is a chronic obstructive pulmonary disease (COPD) that permanently effects the way in which one lives. The pathophysiology of emphysema involve the enlargement of airspaces within the alveoli, along with a destroyed alveoli wall. There is no cure for emphysema but there are treatable methods to help make the symptoms much more easier on the patient. This involves making sure that as much gas as possible is exhaled out of the lungs. Smoking seems to be a major causal factor of emphysema, with research showing that a majority of COPD cases are because of cigarette smoking. Saying this, it does not mean that a non-smoker would not be able to be diagnosed with emphysema and this is due tot he deficiency of the enzyme alpha1 - antitryspin which is something that us found to be inherited thus making it genetic. Introduction: Emphysema is a chronic obstructive pulmonary disease (COPD) which occurs in the lungs, when an individual is affected by emphysema their air sacs are found to be larger than normal and this is due to the fact that the alveoli in the lungs have been permanently destroyed. As the disease progresses further the alveoli proceeds to have an unusual shape due to the continued enlargement of the air sacs, because of this, during exhalation there is great difficulty in airflow since the alveolar walls have