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.一種由垂體前葉分泌的多肽類激素。促腎上腺皮質(zhì)激素可促進(jìn)...[繼續(xù)閱讀]

    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...[繼續(xù)閱讀]

    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.一種革蘭陽性厭氧桿菌,常見于口腔或咽喉部位。偶呈絲狀 分支形態(tài)。許多放線菌如...[繼續(xù)閱讀]

    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...[繼續(xù)閱讀]

    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 ...[繼續(xù)閱讀]

    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...[繼續(xù)閱讀]

    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.發(fā)生化學(xué)反應(yīng)所需要的能量。在生物系統(tǒng)中,酶可以降低反應(yīng)的活化能,使生理?xiàng)l件下的化...[繼續(xù)閱讀]

    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...[繼續(xù)閱讀]

    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...[繼續(xù)閱讀]

    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. 一種用于治療...[繼續(xù)閱讀]