are components of cell membranes. Phosphatidylethanolamine is found primarily in the inner leaflet of membranes. Modify the molecule below by replacing the "X" to show a phosphatidylethanolamine. You may need to add or remove atoms or bonds. If you make a mistake, you can reset the molecule by clicking on the two red arrows. Phospholipids are present in cell membranes. Phosphatidic add is a minor constituent of cell memt but it is an important intermediate in lipid biosynthesis. Modify the molecule below by replacing the "X" to show a phosphatidic acid (phosphatidate). You may need to add or remove atoms or bonds. Identify the fatty acid at position 1 of glycerol (the "top" fatty acid) in this example.