The lac operon in e. coli consists of genes that code for enzymes necessary for the breakdown of lactose. when lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. when lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. in the absence of glucose (a preferred energy source for bacteria), the protein cap binds to a regulatory site near the lac promoter to activate transcription of the lac operon.

they absorb it i think

not sure

you

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.