In addition to oxygen and carbon dioxide, the circulatory system is the primary delivery system for?

Me the formula cacl2 represents the compound

According to theories of how life began, how did early organic molecules begin to separate from the outside world? a: specialized enzymes were required b: chains of amino acids created a barrier c: formation of microspheres or vesicles d: rna catalyzed the formation of membranes

What characteristic makes a cell membrane selectively permeable