Most plants that grow in a desert environment have the ability to retain water in leaves or paddles ( if cactus ) and have deep roots to collect water that is deep in the ground i hope this helps <span />
The cactus is the best example of a plant that has adapted very well to the desert.
The first adaptation has to do with water storage. Thanks to the long roots it has, it can absorve water from very deep areas. The water stored is stored in adapted vacuoles. The cells of the cactus are adapted to transpirate as little as possible, no to loose water in evatranspiration process.
The second adaptation has to do with it´s thorns. Big, rigid and pointy thorns are the perfect defense tolive in the dessert. Animals will tend to eat plants which will not harm them at all. This is why, thorns are a great protection against hungry eaters.
Oils and fats, which in science are called lipids, are known as amphipathic molecules. These molecules have two distinct ends to them: a water-loving (hydrophilic) side and a water-fearing (hydrophobic) side. While the hydrophilic sides of a lipid will associate with the water in a solution, the hydrophobic sides of the lipid all cluster together to 'hide' from the water. Lipids therefore cluster together and form spheres where the hydrophobic sides are in the center away from the water while the hydrophilic sides are on the outside, associating with the water.
The ability of the atoms within a group to form hydrogen bonds with the water molecules around them makes them hydrophilic. Oxygen and nitrogen atoms readily form hydrogen bonds with water molecules, so any organic molecules that have oxygen or nitrogen atoms bound to their carbon skeletons will be hydrophilic.
For example, if we take the molecule for cholesterol, we see the OH group on the left is hydrophilic and will form hydrogen bonds with water, while the ring structures, which only consist of hydrogen and carbon atoms, are hydrophobic and will not associate with the water.
There are many different kinds of lipids with different functions. Lets start by examining phospholipids, which compose the cell membranes of animals. They form lipid bilayers, with one set of hydrophilic heads facing the exterior of the cell membrane and the other set facing the interior (as you can see on the diagram on screen). The hydrophobic portions of the lipid bilayer - the lipid tails - face towards one another, which allows them to hide away from the water inside and outside of the cell.
So,the right answer is option A "amphipathic molecules".
