Fat is essential for building the membranes that surround nerves and cell membranes, which are important external parts of all cells. It is important for blood clotting, muscle movement, and inflammation. Some fats are better than others for long-term health. Good fats include monounsaturated and polyunsaturated fats. Proteins are made up of hundreds or thousands of smaller units called amino acids, which are linked together by long chains. There are 20 different types of amino acids that can be combined to make proteins.
Is - two billion dollars is a unit, one unit so it is singular and you use the singular verb think - scientists is a plural, therefore, you must use the plural verb form of think
