Allosteric regulation

A . sufficient facilities for the crew to wash their clothes B . a wash basin in each room C . separate toilet facilities for engineers where their number exceeds six D . All of the above

A . to B . who C . on D . with

A . used only for pollution response B . owned and operated by the US government C . used only within a barge fleeting area D . used only on inland water

A . binding B . bound C . bounded D . bounding

A . A、变送器 B . B、调节器 C . C、定位器 D . D、定值器

A．Only on line resistance B．Only on line inductance C．Only on line capacitance D．On line inductance and line resistance

A．Many？extracellular？signals？acting？via？GPCRs？affect？the？activity？of？the？enzyme？adenylyl？cyclase？and？thus？alter？the？intracellular？concentration？of？the？second？messenger？molecule？cyclic？AMP. B．Most？commonly,？the？activated？G？protein？α？subunit？switches？on？the？adenylyl？cyclase,？causing？a？dramatic？and？sudden？increase？in？the？synthesis？of？cyclic？AMP？from？ATP. C．To？help？terminate？the？signal,？a？second？enzyme,？called？cyclic？AMP？phosphodiesterase,？rapidly？converts？cyclic？AMP？to？ordinary？AMP.？Cyclic AMP phosphodiesterase is continuously active inside the cell. Because it eliminates cyclic AMP so quickly, the cytosolic concentration of this second messenger can change rapidly in response to extracellular signals, rising or falling tenfold in a matter of seconds. D．Cyclic AMP is water-soluble,so it can, in some cases, carry the signal throughout the cell, traveling from the site on the membrane where it is synthesized to interact with proteins located in the cytosol, in the nucleus, or on other organelles. One？way？that？caffeine？acts？as？a？stimulant？is？by？inhibiting？this？phosphodiesterase？in？the？nervous？system,？blocking？cyclic？AMP？degradation？and？thereby？keeping？the？concentration？of？this？second？messenger？high. 此题为多项选择题。