Compare and contrast the roles of the positive cell-cycle regulators negative regulators.

Positive regulators helps in completion or progression of cell cycle while negative regulators are responsible for inhibiting cell cycle.

Explanation:

There are certain regulators at the internal check points of cell cycle division which controls the following

a)  cell replication

b)Apoptosis

c)uncontrolled cell division  

d)Detection and repairing of damaged DNA.

These regulators are known as cell cycle regulators and are two types positive and negative regulators. The ones which help in the progression of cell cycle to its next stage and then to its completion are known as positive regulators while the ones which inhibits the progression of cell cycle are called as negative regulators. For example –  

Positive Regulators - cyclins and cyclin-dependent kinases (Cdks)

Negative regulators - etinoblastoma protein (Rb), p53, and p21

i believe the answer is a or 1

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.