Nucleus for what?
Atom? Animal Cell? Plant Cell? Each have different structures.
X is the dominant allele / curly hair , females have two X chromosomes and males have an X and Y
Phospholipid bilayers are critical components of cell membranes. The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the cell. However, an important function of the cell membrane is to allow selective passage of certain substances into and out of cells.
