80. Genes that code for repressor or activator proteins that regulate metabolic enzymes.
are usually constitutive and produce
their protein products constantly.
b. are usually regulated by a regulon.
are never seen in prokaryotic cells.
d. are always seen in prokaryotic cells but
never in eukaryotic cells.
e. None of the above are true.
​

many phylogenetic trees have a single lineage at the base representing a common ancestor. a lineage that evolved early from the root and remains unbranched is called basal taxon. when two lineages stem from the same branch point, they are called sister taxa.

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explanation:

b. to discover aspects of the natural world.

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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.