Cell membranes are semi-permeable. That is why they can allow only some substances to enter the cell. It basically depends on the size of the molecules. Smaller atoms like water can easily pass through. However, macromolecules such as sugars, oils and proteins cannot easily pass because they contain a long chain of monomers.
Charles Darwin predicted that tetrapods evolved from... to basically sum it up into one word. fish.
We use Uranium in nuclear power plants. Uranium can be recycled by using the waste from fission to build nuclear bombs or to use for fission in nuclear power plants.
Look up photo of heart labeled, I would do it for you but I’m taking a test of my own right now
