You have a different rock with a volume of 30cm3 and a mass of 60g. What is its density? Density is mass divided by volume, so that the density is 60 g divided by 30cm3, which is 2.0 g/cm3.
The RYR1 gene is responsible for producing the protein ryanodine receptor 1. This protein transport calcium ions to the cells for muscle contraction. When this receptor remains open for a long time, you would expect an excess of calcium ions which would result to muscle rigidity. The excess calcium ions would also increase body temperature and produce excess acid.
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".
Phospholipids are lipids that contains a phosphate group, which forms the "head" of the molecule and is hydrophilic (water loving). The "tail" of phospholipids is made of two fatty acids which are hydrophobic (water fearing). The phospholipid in the cell membrane acts as a selectively permeable barrier that regulates what goes in and out of the cell <u>thereby protecting the cell from some external molecules and ions</u>.
