Why is DNA antiparallel? It has double strands complementing each other. The bases in one strand pair with the other bases in the complementary strand. It has a ladder shape. Its double strands run in opposite directions.

DNA is antiparallel because Its double strands run in opposite directions.

Explanation: The antiparallel nature of DNA strands means that as one strand runs in 5'->3' direction, the other strand runs in 3'->5' direction. The two antiparallel DNA strands are not identical in either base sequence or composition rather they are complementary to each other. This means that anywhere thymine base is found in one strand, adenine is present in the other strand and anywhere guanine occurs in one strand, cytosine occurs in the other strand.

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.