The lock-and-key mechanism refers to
a. the complementary shapes of an enzyme and a substrate.
b. the attractive forces between an enzyme and a substrate.
c. the ability of an enzyme to lower the activation energy of a reaction.
d. the ability of an enzyme to “unlock” the products of a reaction.

I believe it would be A =) 
good luck and i hope i helped 

Mitochondria is the cell organelle that produced the energy that is needed in the body system in form of atp, that is why it is called the power house of the cell. energy is needed by the living organisms to carry out the activities which sustain life.  if the mitochondria is destroyed atp will not be produced. if the mitochondria is destroyed, energy production will stop and the affected living organism will not have the energy to carry out the necessary life processes; this will lead to the death of the organism.