A polypeptide hormone secreted by the anterior portion of the pituitary gland. ACTH stimulates the growth of the adrenal cortex as well as the production of a number of steroid hormones (e.g.,cortisol) in the adrenal cortex.一种由垂体前叶分泌的多肽类激素。促肾上腺皮质激素可促进...[继续阅读]

    One of the two major proteins responsible for muscle contraction. Actin and myosin are found in smooth and striated muscle. Actin monomers together with two other proteins,troponin and tropomysin,can polymerize to form long,thin filaments that,together wi...[继续阅读]

    A genus of anaerobic grampositive rods that are often found in the mouth and throat. They occasionally display a branched filamentous morphology. Many,such as A. israelii,are human pathogens.一种革兰阳性厌氧杆菌,常见于口腔或咽喉部位。偶呈丝状 分支形态。许多放线菌如...[继续阅读]

    An antibiotic produced by Streptomyces parvullus that inhibits RNA transcription in both prokaryotes and eukaryotes. It blocks the action of RNA Polymerase I,which synthesizes ribosomal RNA,and forms complexes with DNA by intercalating between G-C pairs,p...[继续阅读]

    Also called a nerve impulse; sequential wave of depolarization and repolarization across the membrane of a nerve cell (neuron) in response to a stimulus. Depolarization is a reversal in the distribution of charge between the inside and the outside of the ...[继续阅读]

    A secondary sewage-treatment process where biological processing of the sewage by microbial activity is the main method of treatment. In this step,sewage that has been previously treated in settling tanks is aerated in large tanks to encourage growth of m...[继续阅读]

    The energy required for a chemical reaction to proceed. In biological systems,enzymes lower the activation energy,allowing chemical reactions to occur faster under physiological conditions.发生化学反应所需要的能量。在生物系统中,酶可以降低反应的活化能,使生理条件下的化...[继续阅读]

    The region of an enzyme that contains a special binding site for substrate(s). This site is uniquely shaped for the exclusive binding of the particular substrate molecule (s) and is the site for the catalytic activity of the enzyme. The threedimensional f...[继续阅读]

    The transport,by cells or cellular compartments,of ions and metabolites through cell membranes against a concentration gradient. This type of transport requires cellular energy in the form of ATP(adenosine triphosphate) hydrolysis. One example found in al...[继续阅读]

    An antiviral antibiotic used to treat herpes virus infections. Acycloguanosine is a derivative of the normal nucleoside,guanosine,in which the sugar,ribose,has been replaced by an ether chain. Acycloguanosine is an inhibitor of viral DNA synthesis. 一种用于治疗...[继续阅读]