Examples include calcium transport, the sodium-potassium ATPase, and sodium-linked transport of glucose or amino acids. Active transport involves movement of molecules against a concentration gradient and therefore, requires energy usually as ATP. There are 2 types of transport, passive or facilitated diffusion and active transport. However, carriers have some properties in common with enzymes in that they are specific, have dissociation constants, exhibit saturation, and can be blocked by specific inhibitors. A carrier is not an enzyme and does not catalyze any chemical reactions. The specific transport of molecules across membranes is mediated by carriers. These gradients are maintained across the cell membrane by preventing ion flux and by the active transport of ions from one side of the plasma membrane to the other. The difference for sodium is 14-fold (140 mM extracellular, 10 mM intracellular) potassium is 35-fold (4 mM extracellular, 140 mM intracellular) magnesium is 4-fold (2 mM extracellular, 0.5 mM intracellular) chloride is 25-fold (100 mM extracellular, 4 mM intracellular). The largest difference is for calcium which shows a 25,000-fold difference (2.5 mM extracellular compared to 0.1 μM). Question: 1 CLASS QUIZ Which of the following ions has a higher concentration inside the cell than in the extracellular fluid? A typical mammalian cell maintains a concentration gradient of many substances, including ions between the extracellular and intracellular fluid. Nevertheless, constructive comments and suggestions from readers are welcome so as to further strengthen this lecture note. The author strongly believes that this teaching material will play a crucial role in promoting the teaching-learning process through delivery of pertinent information to the trainees. Each chapter is also followed by review questions that can enable the reader to use them as self-assessment tools. Within each chapter, important topics are identified and discussed in simple language so as to facilitate rapid reading and understanding of important concepts. This lecture note is divided into fifteen chapters covering major and relevant topics of the subject matter. In the development of this lecture note, materials have been gathered and adapted from different standard books. It can also be helpful for those graduates who are in service. This lecture note is primarily prepared for Animal Health Science and Veterinary Laboratory Technology and students pursuing their studies in various higher teaching institutions. Therefore, this lecture is developed to fill the existing gap and strengthen the teaching learning processes. Hence, some of the strategies that are used to skirt these problems are developing of lecture notes on various subjects. There is shortage of references in higher teaching institutions especially in newly opened institutions engaged in training of various Veterinary professionals in the country.
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