Final answer:
1) amphipathic. Lipids with polar and nonpolar ends are called amphipathic. This property is crucial for forming cellular structures such as the phospholipid bilayer in cell membranes.
Step-by-step explanation:
Lipids with both polar and nonpolar ends are known as amphipathic molecules. This unique characteristic allows them to play a crucial role in cellular structures such as the cell membrane. A common example of an amphipathic lipid is the phospholipid, which has a hydrophilic (water-loving) 'head' and hydrophobic (water-fearing) 'tails'. The polar head region is attracted to water, thus facing the aqueous environments inside and outside the cell, while the nonpolar tails face each other, avoiding water. This organization forms a lipid bilayer, which is essential for the structure and function of cellular membranes, allowing them to separate and protect the cell's internal environment from the external environment. Additionally, this amphipathic nature facilitates the formation of micelles and liposomes, which are important for lipid transport and metabolism.