A scientist is examining the role of an element found in fats and carbohydrates of living things. This element makes up 65% of h
uman body mass. Which statement describes the element he is studying? He is studying oxygen, which can also be found in proteins. He is studying oxygen, which is the most abundant element in the atmosphere. He is studying nitrogen, which can also be found in proteins. He is studying nitrogen, which is the most abundant element in the atmosphere.
Answer : Option A) He is studying oxygen, which can also be found in proteins.
Explanation : A scientist is examining the role of an element found in fats and carbohydrates of living things. Oxygen is the element which makes up to 65% of human body mass. This is also found in proteins inside the body.
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".
