Aseries of enzymes catalyze the reaction x → y → z → a. product a binds to the enzyme that converts x to y at a position remote from its active site. this binding decreases the activity of the enzyme. with respect to the enzyme that converts x to y, substance a functions as?

The correct answer is: An allosteric inhibitor.

An allosteric inhibitor is the regulator of an enzyme that binds at a site other than the enzyme's active site. That site is called the allosteric site or regulatory site.

When the regulator binds enzyme usually goes through conformational change. Since the activity of the enzyme in example is reduced, we call it inhibitor, otherwise it would be activator.

The inhibition shown in example is negative feedback (final product turns off the reaction in the initial site).  

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !

i dont know it at allnow im just getting points at this pint