The third step is the phosphorylation of fructose-6-phosphate, catalyzed by the enzyme phosphofructokinase. a second atp molecule donates a high-energy phosphate to fructose-6-phosphate, producing fructose-1,6-bisphosphate. in this pathway, phosphofructokinase is a rate-limiting enzyme. it is active when the concentration of adp is high; it is less active when adp levels are low and the concentration of atp is high. thus, if there is "sufficient" atp in the system, the pathway slows down. this is an example of

Efficiency is the percent of work put into a machine by the user (input work) that becomes work done by the machine (output work)

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

The instructions for making proteins come originally from