The lac operon is responsible for the production of a regulatory molecule polypeptides that permit e. coli to use a specific sugar as a carbon source for metabolic energy. the lac operon acts as a genetic switch to begin sugar break down, but only if
(1) lactose is present in the cell; and
(2) all glucose has been depleted.

Drag each tile to the correct box. the body monitors the levels of oxygen in the blood to regulate breathing. isabel is running in a marathon and is near the finish line. she feels out of breath. how will her nervous system work to generate a reaction? arrange the tiles in chronological order. isabel's breathing rate increases. sensory receptors in the arteries detect low oxygen levels. the brain sends signals through motor neurons. sensory neurons generate an impulse. the central nervous system relays an impulse to certain brain regions.