What does the e symbol represent

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

What is the next step in the process after a substrate enters the active site of an enzyme

Identify two examples of chemical reactions that you have encountered during the last week. identify an exothermic and endothermic reaction. explain.