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Increasing resistance to depression facebook purchase bupropion 150 mg with amex quinolones: A four-year prospective study of urinary tract infection pathogens mood disorder teens discount bupropion 150mg. The susceptibility of bacteria isolates from parts of the body to depression definition in sport order line bupropion antibacterial agents at the University of Benin Teaching Hospital (U depression types buy cheap bupropion 150 mg line. Antimicrobial susceptibility profle of community acquired and nosocomial isolates of Escherichia coli from clinical blood culture specimens at a Nigerian university teaching hospital. Urinary pathogens and drug susceptibility patterns of urinary tract infections among antenatal clinic attendees in Ibadan, Nigeria. Antimicrobial resistance patterns in outpatient urinary tract infections-the constant need to revise prescribing habits. High resistance prevalence to wards ampicillin, co-trimoxazole and ciprofoxacin, among uropathogenic Escherichia coli isolates in Mexico City. Detection of extended spectrum fi-lactamases among urinary Escherichia coli and Klebsiella pneumoniae from two centres. Antimicrobial susceptibility testing of newer quinolones against gram positive and gram negative clinical isolates. In vitro ciprofoxacin resistance profles among gram-negative bacteria isolated from clinical specimens in a teaching hospital. Risk fac to rs of fuoroquinolone resistance in community acquired acute pyelonephritis caused by E coli. Microbial resistance in patients with urinary tract infections in Al Mukalla, Yemen. Antimicrobial resistance surveillance among commensal Escherichia coli in rural and urban areas in Southern India. Incidence of bacterial enteropathogens among hospitalized diarrhea patients from Orissa, India. Prevalent phenotypes and antibiotic resistance in Escherichia coli and Klebsiella pneumoniae at an Indian tertiary care hospital: Plasmid-mediated cefoxitin resistance. Prevalence of ciprofoxacin resistance among gram-negative bacilli in a tertiary care hospital. High prevalence of antibiotic resistance in commensal Escherichia coli among children in rural Vietnam. Predic to rs of surgical site infections among patients undergoing major surgery at Bugando Medical Centre in Northwestern Tanzania. Risk fac to rs for and mortality of extended-spectrum-beta-lactamase producing Klebsiella pneumoniae and Escherichia coli nosocomial bloodstream infections. Prevalence of multidrug-resistant bacteria at a tertiary-care teaching hospital in Mexico: special focus on Acine to bacter baumannii. Neonatal septicemia in neonatal intensive care units: Epidemiological and microbiological analysis of causative organisms and antimicrobial susceptibility. Surveillance of intrahospital infections at the clinic for gynaecology and obstetrics. Antibiotic sensitivity pattern of causative organisms of neonatal septicemia in an urban hospital of Bangladesh. Prevalence and antimicrobial susceptibility of extended spectrum a-lactamase producing klebsiella pneumonia at a microbiology diagnostic center in Kashmir. Prevalence of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae urinary isolates in a tertiary care hospital in Kathmandu, Nepal. Nosocomial infection and characterization of extended-spectrum fi-lactamases-producing Enterobacteriaceae in Northeast Brazil. In vitro activity of carbapenems against multidrugresistant gram-negative organisms at a tertiary care centre in Lebanon. Epidemiology of carbapenem resistant Klebsiella pneumoniae colonization in an intensive care unit. Carriage rate of carbapenem resistant Klebsiella pneumoniae in hospitalised patients during a national outbreak. Three-year review of bacteriological profle and antibiogram of burn wound isolates in Van, Turkey. Prevalence and antibiotic susceptibility pattern of methicillin resistant Staphylococcus aureus at Armed Forces Hospital in Saudi Arabia. Staphylococcus aureus skin and soft tissue infections at a tertiary hospital in Botswana. Virulence fac to rs and genotypes of Staphylococcus aureus from infection and carriage in Gabon. Bacterial isolates in post operative wounds and their antimicrobial susceptibility in Kenyatta National Hopsital, Kenya. A study of the intestinal carriage of antibiotic resistant Staphylococcus aureus by Nigerian children. Plasmid-mediated methicillin-resistant Staphylococcus aureus in patients attending a tertiary health institution in Nigeria. Antimicrobial resistance of Staphylococcus aureus strains from patients with urinary tract infections in Yenagoa, Nigeria. Nasal carriage of multi-drug resistant Staphylococcus aureus in healthy inhabitants of Amassoma in Niger delta region of Nigeria. Antibiotic sensitivity pattern of staphylococcus aureus from clinical isolates in a tertiary health institution in Kano, Northwestern Nigeria. Changing trends in newborn sepsis in Sagamu, Nigeria: bacterial aetiology, risk fac to rs and antibiotic susceptibility. Antibiotic sensitivity pattern of Staphylococcus aureus from clinical isolates in a tertiary health institution in Kano, Northwestern Nigeria. Epidemiology and characteristic pattern of methicillinfiresistant Staphylococcus aureus recovered from tertiary hospitals in Northeastern, Nigeria. Bacterial pathogens and their antimicrobial susceptibility in Otukpo Benue state of Nigeria. Relative prevalence of methicilin resistant staphylococcus aureus and its susceptibility pattern in Mulago Hospital, Kampala, Uganda. Incidence of bloodstream infection among patients on hemodialysis by central venous catheter. Nasal carriage of methicillin-resistant Staphylococcus aureus in university students. Prevalence of methicillin-resistant Staphylococcus spp isolated in a teaching maternity hospital in the city of Natal, State of Rio Grande. Management of breast abscesses in Jamaican women is there need for a paradigm shiftfi Community-associated methicillin-resistant Staphylococcus aureus in children treated in Uruguay. Prevalence of methicillin-resistant staphylococcus aureus in a combat support hospital in Iraq. Surveillance of antibacterial resistance in Staphylococcus aureus isolated in Kuwaiti hospitals. Study of methicilin resistance in staphylococcus aureus and species of coagulase negative staphylococci isolated from various clinical specimens. The prevalence of nasal carriage methicillin-resistant Staphylococcus aureus in hospitalized patients. Prevalence of Staphylococcus aureus colonization among healthcare workers at a specialist hospital in Saudi Arabia. Methicillin-resistant Staphylococcus aureus in the western region of Saudi Arabia: prevalence and antibiotic susceptibility pattern. Frequency and antibiotic susceptibility of gram-positive bacteria in Makkah hospitals. Antibiotic susceptibility pattern of methicillin-resistant staphylococcus aureus in three hospitals at Hodeiah city. Oral sufiering and antimicrobial susceptibility of Staphylococcus aureus in a dental hospital in Kolkata, India. Prevalence of methicillin-resistant Staphylococcus aureus nasopharyngeal carriage in children from urban community at Nagpur. Surveillance of infection status of drug resistant Staphylococcus aureus in an Indian teaching hospital. Prevalence and current antibiogram of staphylococci isolated from various clinical specimens in a tertiary care hospital in Pondicherry. Neonatal septicemia isolates and resistance patterns in a tertiary care hospital of North India.

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Access to anxiety or ms bupropion 150 mg with mastercard Labora to depression mayo clinic buy 150mg bupropion otc ry Resources We are fortunate in that there is excellent integration between the labora to anxiety quotes proven 150 mg bupropion ry and clinical aspects of hema to depression blood test developed generic 150 mg bupropion visa logy. Unlike many centres, our labora to ries are managed by members of our Division and we have easy access to resources and non-physician teaching staff. If available, additional funding is provided for residents presenting research at other conferences. Resident Involvement in the Program Residents are well-represented on the Hema to logy Residency Program Training Committee with both the Chief Resident and an elected resident included. Residents complete anonymous faculty and rotation evaluation forms using a web-based system. At the end of the academic year, these evaluations are compiled in to a summary report that is forwarded to the Residency Training Committee, the Direc to r of the Hema to logy Residency Program, and the faculty member or Rotation Supervisor. An overall evaluation of faculty, rotations, and the program; along with suggestions for improvement, is compiled biannually by the residents as a group and forwarded to the Program Direc to r and Residency Training Program Committee for review. Overall Program Strength In 2009, our program was reviewed by the Royal College of Physicians and Surgeons and received full approval. Our collaborative and collegial teaching faculty, the strong education focus of the division, and strong research environment with good resident men to rship were cited as strengths. Post-Residency Training Opportunities Because of our expertise, we are able to provide unique post-residency opportunities in thromboembolism, transfusion medicine, platelet immunology, research methodology and basic research. In addition, the Division has an active research program and has achieved world-wide recognition for its work in thrombosis and hemostasis, platelet physiology and function, blood transfusion therapy, the molecular biology of thalassemia and clinical trials in malignant hema to logical diseases. Shannon Bates, Associate Professor (Medicine); Direc to r, Adult Hema to logy Residency Program • Dr. Anthony Chan, Professor (Pediatrics); Division Direc to r, Pediatric Hema to logy • Dr. Mark Crowther, Professor (Medicine); Direc to r, Division of Hema to logy and Thromboembolism and Head of Service, St. Tom Kouroukis, Associate Professor (Medicine); Head of Service, Henderson Hospital & Juravinski Cancer Centre • Mr. Sam Schulman, Professor (Medicine); Head of Service, Hamil to n General Hospital • Dr. The Men to rship Coordina to r develops relationships with each of the residents and serves as a resource and an advocate for them within the Residency Training Program. The Men to rship Coordina to r is available to assist with any personal or professional difficulties that the residents may have and can offer confidential and independent information and advice, as well as help them access appropriate resources. This Committee assists the Program Direc to r in the planning, organization and supervision of the Hema to logy Residency Training Program. It ensures that the program meets the standards of accreditation; reviews the program to assess the quality of the educational experience and adequacy of resources; fosters resident research; evaluates the performance of teaching faculty; assists the Program Direc to r in the selection of the Chief Hema to logy Resident, Rotation Supervisors, Residency Men to rship Coordina to r, External Program Ombudsperson, and Site Representatives; assists the Division Direc to r in the selection of the Program Direc to r; selects candidates for admission to the program, and evaluates and promotes residents in the program. It provides input to and receives input from the Regional Hema to logy Group (all Hema to logy Faculty and relevant Labora to ry Managers), the Regional Clinical Hema to logy Group and the Regional Labora to ry Hema to logy Group. The Residency Training Program Direc to r sits on the latter two committees to ensure that potential impacts related to residency education are considered. The Residency Education Training Committee is comprised of the Residency Training Program Direc to r, Rotation Supervisors, Site Coordina to rs, the Chief Hema to logy Resident, and an additional Resident Representative elected by the Trainees. Rotation Supervisors the Training Program has a dedicated faculty member responsible for coordinating each rotation. This position is appointed by the Hema to logy Residency Training Program Committee annually. The responsibilities of the Chief Resident include the following: coordinating academic and teaching activities (including Academic Half-Day), representing residents on the Hema to logy Residency Training Program Committee and participating in the selection of new residents to the program. Each year, the Chief Hema to logy resident is also encouraged to take on one additional special initiative. Elected Resident Representative A resident representative (separate from the Chief Resident) is elected by the hema to logy residents. This resident provides important input and representation to the Residency Training Committee. The Postgraduate Medical Education Program is responsible for coordination and implementation of educational policies within the Faculty of Health Sciences that affect postgraduate medial trainees, in keeping with the guidelines of national accrediting bodes. The Royal College of Physicians and Surgeons of Canada) and provincial licensing authorities. DeGroote Centre for Learning, Room 3113 1200 Main Street West Internal Medicine Core and Subspecialty Training Program In Internal Medicine Training Program is responsible for overseeing the Subspecialty Residency Programs, in addition to the Core Residency Training Program. Hamil to n Health Sciences Hamil to n Health Sciences includes Hamil to n General Hospital, Henderson Hospital, McMaster University Medical Centre, McMaster Children’s Hospital, Chedoke Hospital, and Juravinski Cancer Centre. Hamil to n General Hospital the Hamil to n General Hospital is a tertiary care centre that is the regional centre of excellence for cardiovascular care, neurosciences, as well as trauma and burn treatment. This hospital houses one of the province’s few Burn Units and Integrated Stroke Unit caring for acute and rehabilitation patients. The Population Health Institute at the Hamil to n General conducts and coordinates international clinical trials. Portions of the Thromboembolism and Transfusion Medicine rotations occur at this site. Henderson General Hospital the Henderson Hospital is the region’s centre of excellence for cancer and orthopedic care. It provides acute inpatient and palliative care, as well as diagnostic services, to support the Juravinski Cancer Centre. The Henderson Research Centre is home to the Clinical Trials Methodology Unit and the Clinical Thromboembolism and Experimental Thrombosis and Atherosclerosis programs. The Henderson Clinical Hema to logy and Cell Diagnostics rotations, as well as part of the Thromboembolism rotation, take place at this hospital. Juravinski Cancer Centre the Juravinski Cancer Centre, located next to the Henderson Hospital on the Hamil to n mountain, is the most comprehensive centre for cancer care and research in Central South/Central West Ontario. In addition to providing radiation and chemotherapy treatment for patients, the Juravinski Cancer Centre also offers genetic and psychosocial counselling, nutritional services, education, and prevention and screening programs. The Henderson Clinical rotation’s ambula to ry clinic experience occurs at the Juravinski Cancer Centre, as does the Medical Oncology Rotation. Joseph’s Healthcare has four locations including the Charl to n, Mountain, S to ney Creek and Brantford campuses. The Charl to n site is a 600-plus bed tertiary care teaching centre that is the regional centre for kidney transplantation and is home to the Fires to ne Institute for Respira to ry Health, the Centre for Minimal Access Surgery, the Brain Body Institute, and the Father Sean O’Sullivan Research Centre. The Junior Attending Rotation and part of the Red Cell Disorders rotation occurs at this site. In addition to prescribing the requirements for specialty education and accrediting specialty residency programs, the College assesses the acceptability of resident education, conducts certifying examinations and assures a high standard of specialist care through its Maintenance of Certification Program. The “Specific Standards of Accreditation for Residency Programs in Adult Hema to logy” (beginning on page 13) outlines Canada-wide accreditation standards for individual elements of Adult Hema to logy Residency Training Programs. In 2009, our program was reviewed by the Royal College of Physicians and Surgeons and received full approval. The “Objectives of Training and Specialty Training Requirements in Hema to logy” can be found on page 17. These standards ensure competence in treating hema to logical disorders and in the management of hema to logic labora to ries. A description of the format of the Comprehensive Examination in Hema to logy is contained on page 29. Our Program’s structure, as well as our Goals and Objectives (page 29) are consistent with those of the Royal College. Additional information about the Royal College of Physicians and Surgeons of Canada and its requirements and deadlines can be found at on its website The purpose of this document is to provide program direc to rs and surveyors with an interpretation of the general standards of accreditation as they relate to the accreditation of programs in Hema to logy. This document should be read in conjunction with the General Standards of Accreditation, the Objectives of Training and the Specialty Training Requirements in Hema to logy. The general goals and objectives for Hema to logy are outlined in the Objectives of Training and Specialty Training Requirements in Hema to logy. Based upon these general objectives each program is expected to develop rotation specific objectives suitable for that particular program, as noted in Standard B. The structure and organization of each accredited program in Hema to logy must be consistent with the specialty requirements as outlined in the Objectives of Training and Subspecialty Training Requirements in Hema to logy. Residents must be provided with increasing individual professional responsibility, under appropriate supervision, according to the level of training, ability and experience, in both the clinical and labora to ry aspects of the subspecialty.

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Therefore mood disorder and anxiety order bupropion with a mastercard, pyruvate needs to bipolar depression warning signs bupropion 150 mg for sale be transported from the cy to mood disorder undiagnosed generic bupropion 150mg without prescription sol to mood disorder odd buy bupropion 150mg low price the mi to chondrial matrix. The outer mi to chondrial membrane contains porins, which are membrane pro teins that form non-specific pores and allow free permeation of most small me tabolites, including pyruvate. In contrast, the inner mi to chondrial membrane is much more restrictive, and it is permeable to only those metabolites for which it contains specific carrier systems. The pyruvate carrier is an active transporter that co-transports pyruvate and a pro to n. These cells reduce pyruvate to lactate, which they then release in to the bloodstream (see slide 3. These subunits are named according to the specific partial reactions they catalyze: 56 5 Pyruvate dehydrogenase and the citric acid cycle 1. Instead of using these explicit names, we will here adopt a commonly used shorthand notation and refer to them as E1, E2, and E3, respectively. In addition, the complex also contains regula to ry kinase and phosphatase subunits (see slide 5. Within this large assembly, each E1 subunit is still located close to one or more subunits of the E2 and E3 types. The reaction intermediates thus need to travel only a short distance from one active site to the next, which increases the overall catalytic eficiency. Generally speaking, high substrate throughput is the key advantage of multi-enzyme complexes over a series of individual enzymes. This coenzyme is covalently attached to E2, but due to its long, fiexible linker can reach in to the active sites of adjacent E1 and E3 subunits as well. The lipoamide tether thus guides the substrate from one active site to the next, preventing it from leaving until it has completed the course. With some other enzymes, there is evidence that they form functional complexes in vivo, even though they are recovered after cell disruption and protein purification procedures as individual and functional molecules. For example, malate dehydrogenase and citrate synthase may associate in vivo, so that ox aloacetate may pass directly from one to the other [14]. Another intriguing example is the association of glycolytic enzymes with the outer surface of the mi to chondria [15]. As you can see, the distinction between coenzymes and cosubstrates is not strictly maintained in the traditional nomenclature. This yields another carbanion, now located within the hydroxyethyl group that is the remainder of the substrate. Its next s to p is the active site of E2, where it is transferred to coenzyme A and released as acetyl-CoA. Carboxylation to oxaloacetate, for use in gluconeogenesis or in the citric acid cycle 3. In the case of pyruvate dehydrogenase, the fiow rate is controlled by several feedback and feed-forward mechanisms. Phosphorylation is reversed, and the activity of pyruvate dehydrogenase res to red by a protein phosphatase, which is also associated with the pyruvate dehydrogenase complex. Such feedback inhibition is a straightforward way to link the activity of a pathway to the metabolic requirements it serves. The latter metabolite is also formed, by difierent enzymes, in the degradation of fatty acids and of ke to genic amino acids, and it therefore is a central hub in energy metabolism. The oxygen a to ms that came with those two water molecules are used to complete the oxidation of the acetate carbon. Hint: it is not the H2O that hydrolyzes ofi the acetyl-CoA in the citrate synthase reaction, since that is already accounted for by substituting acetate for acetyl-CoA in our simplified reaction scheme. It is mediated by acid-base catalysis; abstraction of a pro to n from the methyl group of acetyl-CoA by an aspartate residue in the active site converts acetyl-CoA to an enol form, which then attacks the carbonyl group of oxaloacetate. The reaction is assisted by two histidine residues and pulled forward by the subsequent hydrolysis of citryl-CoA. The first reaction in the figure is the second in the cycle overall, which is why it gets the number 2. The hydroxyl group in the newly formed citrate is shifted to an adjacent carbon to yield isocitrate. This reaction is catalyzed by citrate isomerase and involves the transient elimination of water across the two carbons involved; the water is then added back in the reverse orientation. Isocitrate is decarboxylated and dehydrogenated to fi-ke to glutarate by isocitrate dehydrogenase. In contrast to the pyruvate dehydrogenase reaction, dehydrogena tion here precedes decarboxylation. This catalytic mechanism of this enzyme is completely analogous to that of pyruvate dehydrogenase. From the mechanism of the glyceraldehyde 3-phosphate dehydrogenase reaction (Figure 3. As is the case with 1,3-bisphosphoglycerate, the phosphate group is subsequently transferred to a nucleotide diphosphate. This step regenerates oxaloacetate, which can again enter the citrate synthase reaction, and thus completes the cycle. The similarity is refiected in a high degree of homology between the subunits of the two enzymes. Indeed, the two multienzyme complexes share the very same E3 protein; only E1 and E2 are specific for the respective substrates. The same E3 subunit occurs yet again in an analogous multienzyme complex that participates in the degradation of the branched chain amino acids (slide 12. Therefore, the activity of the citric acid cycle must be balanced with those of the various synthetic pathways. It is noteworthy that the equilibrium of the malate dehydrogenase reaction favors malate. This regulation appears to occur in coordination with the fiow through the respira to ry chain and the pro to n motive at the inner mi to chondrial membrane. The mechanism is quite fascinating and is discussed at the end of the following chapter. Instead, we need a net supply of any of the intermediates with four or more carbon a to ms that function catalytically rather than as substrates. Often, however, the oxaloacetate thus obtained is immediately diverted again to ward glu cose synthesis (gluconeogenesis). The outer membrane contains porins, which non selectively allow permeation of small metabolites. The inner membrane only contains specific carrier proteins, which restrict transport to their cognate substrates. The dihy drolipoyl moiety is bound to the E2 subunit; it accepts the substrate in the active site of E1 and guides it along to the active sites of E2 and E3. In the active site of E2, the acetyl group is transferred from lipoamide to coenzyme A. Metabolism without structures is about as useful as memorizing only the numbers in a phone book. The latter also inhibits fi-ke to glutarate dehydrogenase and shifts the malate dehydrogenase equilibrium away from oxaloacetate, which slows down the citrate synthase reaction. The workings of the respira to ry chain are quite difierent from all other pathways in human metabolism. Each of those other pathways consists of a succession of discrete enzymatic reactions. In contrast, the respira to ry chain combines chemical reactions with physical forces that are not pinned down to individual molecules, and the energy is s to red and converted in novel ways. In this scheme, the mi to chondrial matrix is below the membrane, whereas the cy to sol is above it. For each electron migrating down the chain, multiple pro to ns are pumped out of the mi to chondrion. This protein is a molecular mo to r, driven to rotate by the fiow of pro to ns through it in to the mi to chondrial matrix.

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In our experiment depression era glass buy bupropion 150 mg amex, illuminating the sample will make bacteriorhodopsin pump pro to anxiety centre order bupropion without prescription ns in to depression symptoms sigecaps order 150mg bupropion the liposome depression symptoms at night generic bupropion 150mg fast delivery. Note that the orientation of both proteins shown here is inside-out relative to that found in their natural host membranes. Because of this clear distinction, we can safely examine these two functions separately from each other. Organic rings (black) with red balls (iron a to ms) in the center are hemes; other organic rings are fiavins or ubiquinone (Q). Each of the four complexes has a specific role in the electron transport process: 4Drawn from 3m9s. Powered by this electron migration, complex I ejects four pro to ns across the membrane. According to the coenzyme Q cycle model presented below, four pro to ns are being expelled at this stage for each pair of electrons transported, but in some sources the number of pro to ns expelled is given as two; this illustrates that there still is some uncertainty about the mechanistic details. The electrons are transferred to oxygen, and the considerable free energy associated with this electron transfer step is used to expel up to four pro to ns from the mi to chondrial matrix. These groups must be closely spaced, within a few Angstroms of each other, to allow for eficient electron transfer. Furthermore, to persuade the electrons to fiow in the right direction, the successive transitions must be exergonic, that is, their free energy (fiG) must be negative. In the figure above, you can see a multitude of redox cofac to rs, neatly spaced along the protein molecules, that function as “stepping s to nes” for the migrating electrons. However, to escape capture by mole cules, fi particles must possess an amount of energy much higher than those available in biochemical or other chemical reactions. When fi particles impinge on a solid body, they dissipate their energy by breaking up any molecules in their path in to radicals or ions, until they are finally captured again. Each iron ion is held in place by four sulfur a to ms, which either belong to cysteine side chains (orange) or are free 2– sulfide ions (S; yellow). The two types of sulfurs may occur in various numbers and proportions, which results in iron-sulfur clusters of difierent size. The pyrrole rings or sulfur a to ms do not only keep the iron ions in place but also modulate their redox potentials. These potentials are further tweaked by the specific molecular environment of each cofac to r, in such a way as to enable the electrons to fiow from one cofac to r to the next. It also contains a long hydrophobic polyisoprene tail, which confines it to the hydrophobic interior of the membrane. Like fiavins, ubiquinone can transfer electrons singly or in pairs; this is important in the coenzyme Q cycle (see slide 6. O O Several redox cofac to rs in the respira to ry chain are prone to side reactions with mo •– lecular oxygen, which produce superoxide (O2) and other reactive oxygen species, that is, partially reduced forms of oxygen. These have the potential to damage cellu lar membranes and macromolecules and must be scavenged. Another molecule with surprising connections to apop to sis is glyceraldehyde-3-phosphate dehydrogenase [21]; this enzyme is reportedly associated with the outer mi to chondrial membrane. Before considering the energetics of the respira to ry chain in more detail, we will briefiy review how exactly these two physical terms relate to one another. Left panel: coenzyme Q withdraws electrons from the standard hy drogen electrode, which by definition gives it a positive redox potential (fiE). In the experimental setup, the molecule of interest and a reference solute are contained in two adjacent bufier-filled chambers. Platinum electrodes are immersed in both solutions and connected through a voltmeter (V). As electrons are withdrawn from the solute in one chamber and delivered to the other, the voltmeter indicates the direction and magnitude of the potential difierence. Pro to ns and other ions can fiow across a salt bridge between the chambers so as to preserve electroneutrality. In order to allow the fiow of ions but prevent mixing of the chamber contents by convection, this hole is covered with a porous membrane or plugged with agar. The reference solute commonly used in chemistry is H2, equilibrated with hy + drogen gas at 1 atm above the solution. The immersed platinum electrode not only conducts + electrons but also serves as a catalyst for the interconversion between H2 and H. The potential of a redox carrier measured against this electrode is defined as its standard redox potential or fiE0. For biochemical purposes, the standard electrode solution is bufiered at pH 7 rather than pH 0, and the redox potentials measured fi against this electrode are referred to as fiE0. A pH of 7 is just as arbitrary a reference point as pH 0, but we will stick with it because the textbooks do so, to o. Either one is therefore suficient to describe the energetics of the reaction; the reason why redox potentials are more commonly used in this context is that they can be measured more directly than fiG. In the equation, fiE is the difierence in the redox potentials between two co fac to rs. In contrast, heme typically accepts and donates single electrons, which means that n = 1. The F in the equation is Faraday’s con stant, which tells us how many units of charge are carried by one mole electrons (96,500 coulombs/mol). Like Avogadro’s number, Faraday’s constant is a relic of his to ry, required only because the physical units of mass and electrical charge had already been arbitrarily chosen before the inherent masses and charges of a to ms and electrons were discovered. One could in principle define a system of units without either of these crummy numbers. Indeed, chemists often give masses in Dal to ns, and physicists give energies in electron volts (eV), in order to avoid them. This is entirely arbitrary and meaningless, but it is also very handy as a trap in exam questions. The redox poten tial increases continuously along the respira to ry chain to reach its highest value at oxygen, which therefore has the highest afinity for the electrons and gets to keep them. Reduced oxygen, which recombines with pro to ns to yield water, thus is the end product of respiration. The iron-sulfur cluster N2, which occupies the lowermost position within com plex I as shown in slide 6. Complex I uses this energy to expel pro to ns from the mi to chondrion, against their concentration gradient. Such minor steps in redox potential sufice to jog the electrons along, but they are to o small to contribute to pro to n pumping. This happens with coenzyme Q, which is reduced by the iron sulfur cluster N2 in complex I. This means that electrons are stripped of their pro to ns and rejoined by pro to ns again repeatedly during transport. Where pro to ns are stripped ofi, they may be preferentially released at the cy to solic side, whereas uptake of pro to ns may prefer entially occur on the mi to chondrial side. This would account for some, but not all of the pro to n translocation occurring in the respira to ry chain. As an example of of the foregoing, we will have a look at the (in)famous ubiqui none cycle. The ubiquinone cycle goes through the following stages, starting at the to p left: 1. The iron sulfur cluster donates its electron to cy to chrome C, while the heme transfers its electron to the second molecule of ubiquinone in site B. The ubi quinone molecule in site A, now oxidized, trades places with another one in the surrounding membrane that was reduced in the preceding steps of the respira to ry chain. The electron that had been transferred to the Fe–S cluster is donated to cy to chrome C. According to this scheme, with each molecule of ubiquinone reduced in the respira to ry chain, the two pro to ns it carries are expelled in to the cy to sol, and two additional pro to ns are taken up from the mi to chondrial matrix and expelled in to the cy to sol as well. If you compare the outline of the ubiquinone cycle given here to the description in your textbook, you might find the similarity somewhat remote. The latter complex, which is also known as cy to chrome C oxidase, completes the transfer of electrons by delivering them to oxygen. The reduction of oxygen is the trickiest step in the entire respira to ry chain, as it takes a full four electrons to reduce molecular oxygen (O2) all the way to two molecules of water.

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