Livres sur le sujet « Functional ATPG »

All other things being equal, physiological reaction rate increases roughly exponentially with temperature. Organisms that have adapted over evolutionary time to live at different temperatures can have enzyme variants that exhibit similar kinetics at the temperatures to which they have adapted to operate. Within species whose distribution covers a range of temperatures, there may be differential expression of enzyme variants with different kinetics across the distribution. Enzymes adapted to different optimum temperatures differ in their amino acid sequence and thermal stability. The Gibbs energy of activation tends to be slightly lower in enzyme variants adapted to lower temperatures, but the big change is a decrease in the enthalpy of activation, with a corresponding change in the entropy of activation, both associated with a more open, flexible structure. Despite evolutionary adjustments to individual enzymes involved in intermediary metabolism (ATP regeneration), many whole-organism processes operate faster in tropical ectotherms compared with temperate or polar ectotherms. Examples include locomotion (muscle power output), ATP regeneration (mitochondrial function), nervous conduction and growth.

On a ketogenic diet, ketone bodies provide an alternative fuel, replacing much of the glucose used ordinarily by the brain. This switch is thought to underlie its anticonvulsant effects. Brain fuel utilization can also be modified by a nondietary approach: genetic alteration of the protein BAD, which has known roles in regulating both apoptosis and glucose metabolism. When the metabolic function of BAD is genetically altered in mice, it produces reduced glucose and increased ketone body metabolism in neurons and astrocytes. This effect is related to regulation of BAD by phosphorylation and is independent of its apoptotic function. Mice with BAD modifications that produce decreased glucose metabolism exhibit a marked increase in the activity of neuronal ATP-sensitive potassium (KATP) channels and strong resistance to behavioral and electrographic seizures in vivo. This seizure resistance is lost upon genetic ablation of KATP channels, suggesting that KATP channels mediate BAD’s anticonvulsant effect.

Anthropogenic contaminants with the potential to disrupt biological functions enter aquatic ecosystems from a variety of sources, and pose a potential risk to the long-term sustainability of these ecosystems. Sea urchin embryos and larvae, largely used in developmental biology, have great sensitivity toward environmental perturbations, including several anthropogenic stressors. Much attention has recently been devoted to the sea urchin “chemical defensome,” or genes predicted to be involved in chemical defense to confer resilience and survival to developing embryos, with special attention to the ATP-binding cassette (ABC) transporter genes. The present chapter discusses the role of ABC transporters as the first line of cell defense against both natural and anthropogenic toxicants and their relevance to ecotoxicological studies, including the identification of substrates or inhibitors among natural and anthropogenic toxins and contaminants as well as the circumvention of the multixenobiotic resistance phenotype in realistic exposure scenarios.

The hypoxic response of the host is complex. While the oxygen-sensing intracellular machinery attempts to restore cellular homeostasis by augmenting respiration and blood flow, events such as severe haemorrhage lead to whole body hypoxia and decreased mitochondrial function. Immunological perturbations following severe haemorrhage may result in multiple organ dysfunction and sepsis, while impaired perfusion may lead to microvascular injury and local hypoxia. Trauma-haemorrhage or hypoxic exposure in animals causes a systemic inflammatory response, decreased antigen presentation by peritoneal macrophages, hypoxaemia and initiation of endoplasmic reticulum stress. In response, the protein level of the oxygen-sensing transcription factor, hypoxia inducible factor (HIF)-1 increases; this leads to the regulation of expression of a number of genes resulting in decreased mitochondrial ATP production, but enhanced glycolytic processes, thus shifting the energy balance. In addition, sustained tissue hypoxia leads to increased free radical production and cellular apoptosis. Though the initial host response to hypoxia may be protective, sustained hypoxia becomes detrimental to the tissues and the organism as a whole.

Inorganic phosphate ions (H2PO4−/ HPO42−) (abbreviated as Pi) are involved in formation of bone and generation of high-energy bonds (e.g. ATP), metabolic pathways, and regulation of cellular functions. In addition, Pi is a component of biological membranes and nucleic acids. Only about 1% of total body Pi content is present in extracellular fluids, at a plasma concentration in adults within the range 0.8–1.4 mMol/L (at pH 7.4 mostly as HPO42−), with diurnal variations of approximately 0.2 mM. A small amount of plasma Pi is bound to proteins or forms complexes with calcium. Under normal, balanced conditions, absorption of dietary Pi along the small intestine equals the output of Pi via kidney and faeces. Renal excretion of Pi represents the key determinant for the adjustment of normal Pi plasma concentrations. Renal reabsorption of Pi occurs along the proximal tubules by sodium-dependent Pi cotransporters that are strictly localized at the apical brush border membrane. Parathyroid hormone (PTH) and FGF23 are key regulators amongst a myriad of factors controlling excretion of Pi in urine, mostly by changes of the apical abundance of Na/Pi cotransporters. Hypophosphataemia may result in osteomalacia, rickets, muscle weakness, and haemolysis. Hyperphosphataemia can lead to hyperparathyroidism and severe calcifications in different tissues.

Prekladaný vysokoškolský učebný text „Bioenergetika“ by mal slúžiť ako úvod do problematiky štúdia v oblasti bioenergetiky. Táto vedná oblast je v súčasnosti vysoko aktuálna, pretože výsledky získané bioenergetickým výskumom v uplynulých rokoch zreteľne ukazujú, že bioenergetické procesy prebiehajúce v živých systémoch neslúžia “len” na transformáciu energie, ale ovplyvňujú aj priebeh procesov ako sú apoptóza, starnutie, vznik a rozvoj mnohých ochorení (predovšetkým neurodegeneratívnych). Tieto skutočnosti jednoznačne naznačujú potrebu existencie kvalitných učebných textov, ktoré by prijateľným spôsobom umožnili študentom získať potrebné informácie a vedomosti v tejto vednej discipline. Z vyššie uvedených dôvodov sme sa rozhodli vytvoriť tieto učebné texty, ktoré sú vo forme desiatich samostatných kapitol, ktoré však na seba prirodzene a logicky nadväzujú. Jedna kapitola predstavuje v podstate jednu prednášku v rámci kurzu Bioenergetiky, ktorý je realizovaný na Prírodovedeckej fakulte Univerzity Pavla Jozefa Šafárika v Košiciach na magisterskom a doktorandskom stupni študijného programu „Biofyzika“. Zároveň tieto texty môžu poslúžiť aj pri výučbe v študijnom predmete Biochémia, ktorý je prednášaný v bakalárskych a magisterských stupňoch študijných programov “Biochémia” resp. “Biofyzika”. Dovoľujeme si vyjadriť presvedčenie, že tieto učebné texty by mohli byť istým spôsobom nápomocné aj vedeckým pracovníkom pracujúcim v oblasti výskumu týkajúcho sa problematiky transformáci energie v biologických organizmoch a fenoménoch spojených s touto transformáciou. V týchto učebných textoch sú postupne uvádzané poznatky týkajúce sa základných konceptov bioenergetiky, mechanizmov procesov ako sú glykolýza a Krebsov cyklus (okrem podrobného a uceleného popis týchto procesov je tu uvedený aj všeobecný náhľad o prepojenosti týchto procesov ako aj ich začlenenie do kompaktného pohľadu na celkový proces transformácie energie v biologických organizmoch), zloženia štruktúry a funkčnosti biologických membrán (táto oblast je nevyhnutná pre lepšie pochopenie poznatkov, ktoré sú uvedené v nasledujúcich kapitolách). V nasledujúcich kapitolách sa učebný text zaoberá popisom štruktúry a funkcie mitochondrií, pričom veľký dôraz je dávaný na popis vlastností a mechanizmov fungovania štyroch komplexov dýchacieho reťazca a ATP-syntázy. Tieto komplexy vytvárajú podmienky pre existenciu “najdôležitejšieho” bioenergetického procesu, oxidatívnej fosforylácie. V záverečných dvoch kapitolách sú uvedené mechanizmy procesov vytvárajúcich fotosyntézu, jej svetlej aj tmavej fázy. Sú tu relevantné informácie o tomto “druhom” najdôležitejšom bioenergetickom procese prebiehajúcom v mnohých biologických organizmoch a poskytujúcom možnosť transformácie enrgie elektromagnetického žiarenia na energiu “ukrytú” v chemických väzbách určitých chemických molekúl. Chceme vyjadriť naše presvedčenie, že predložené učebné texty “Bioenergetika” budú dobrým “pomocníkom a inšpirátorom” pre mnohých študentov, ktorí sa budú chcieť dozvedieť čo najviac o fascinujúcich štruktúrach a mechanizmoch umožňujúcich transformáciu energie v živých systémoch, bez ktorej by nebola možná existencia života ako ho poznáme. Želáme príjemné a podnetné čítanie a štúdium. URL: www.unibook.upjs.sk The textbook "Bioenergetics" should serve as an introduction to the study of bioenergetics. This field of science is currently highly actual, as the results of the bioenergetics research in recent years clearly show that bioenergetics processes in living systems can "serve" not only to transformation of energy, but also affect the course of processes such as apoptosis, aging, origin and development of many diseases (especially neurodegenerative). These facts clearly indicate the need for the existence of quality teaching texts that would allow students to acquire the necessary information and knowledge in this scientific discipline in an acceptable way. For the above mentioned reasons, we decided to create these textbooks, which are in the form of ten chapters, which naturally and logically follow each other. One chapter basically presents one lecture within the course of Bioenergetics, which is realized at the Faculty of Science of the Pavel Jozef Šafárik University in Košice at the master's and doctoral degree of the study program "Biophysics". At the same time, these texts can also be used for teaching in the study subject Biochemistry, which is taught in the bachelor's and master's degree programs of the study programs "Biochemistry" resp. “Biophysics”. We would like to express our conviction that these textbooks could in some way also help researchers working in the field of the energy transformation in biological organisms and the phenomena associated with this transformation. These textbooks present knowledge about the basic concepts of bioenergetics, the mechanisms of processes such as glycolysis and the Krebs cycle (in addition to a detailed and comprehensive description of these processes, there is also a general view of the interconnectedness of these processes and their incorporation into a compact view of the overall energy transformation in biological organisms), the structure and functionality of biological membranes (this area is necessary for a better understanding of the knowledge presented in the following chapters). In the following chapters, the textbook deals with the description of the structure and function of mitochondria, with great emphasis on the properties and mechanisms of functioning of the four complexes of the respiratory chain and ATP-synthase. These complexes create the basis for the existence of the "most important" process in bioenergetics, oxidative phosphorylation. In the final two chapters, the mechanisms of the processes that produce photosynthesis, its light and dark phases, are presented. There is relevant information about this "second" most important bioenergetics process taking place in many biological organisms and providing the possibility of transforming the energy of electromagnetic radiation into energy "hidden" in the chemical bonds of certain chemical molecules. We want to express our conviction that the textbooks "Bioenergetics" will be a good "helper and inspirer" for many students who want to learn as much as possible about the fascinating structures and mechanisms for energy transformation in living systems, without which it would not be possible existence of life as we know it.