Final answer:
Aquaporins are regulated by vasopressin, facilitate water transport across membranes, are not dependent on ATP for this function, are transmembrane proteins, and are present in many organisms, not just bacteria.
Step-by-step explanation:
Aquaporins are integral membrane proteins that facilitate the transport of water across cell membranes. Answering the question posed, aquaporins can be regulated by the hormone vasopressin (also known as antidiuretic hormone, or ADH). When ADH binds to receptors on the cells of the collecting tubule in the kidney, it results in the insertion of aquaporins into the plasma membrane, thereby allowing water to be reabsorbed from the urine back into the bloodstream. This helps to concentrate the urine and conserve water in the body, especially under dehydration conditions. Aquaporins do not prevent the passage of water; in fact, they facilitate it. They are not directly dependent upon energy from ATP but can be indirectly affected by ATP when it is used in other cellular processes that regulate their function. Unlike ion channel proteins that can be energy-dependent for active transport, aquaporins facilitate passive transport of water. Aquaporins are not lipid-anchored but are transmembrane proteins. Furthermore, aquaporins are not only present in bacterial cells; they are found in a wide range of organisms including humans, where at least 10 types are known, with six types being identified in the kidney alone. Different aquaporins can also be allosterically regulated and have the ability to transport other molecules such as glycerol, urea, ammonia, carbon dioxide, and even ions in addition to water.