It's actually pretty easy to estimate the first number - all you have to know is the apparent angular size of the sun and moon in the sky (about half a degree each) and the the time it takes the moon to orbit the earth (about one month).
Eukaryotic Organelles. 1  Nucleus-a membrane bound structure that contains the cell's hereditary (DNA) information and controls the cell's growth and reproduction. 2  It is commonly the most prominent organelle in the cell.
Cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. The basic function of the cell membrane is to protect the cell from its surroundings.