<span>Cells that are in multicellular organisms are suited to do specific jobs and work together to help the organism stay alive. Single celled organisms have to perform all the actions themselves in order to stay alive. :) </span>
Most models can't incorporate all the details of complex natural phenomena. For example, when measuring distances around the Earth it's convenient to model the Earth as a sphere, but this doesn't incorporate variations in distance because of mountain ranges, valleys and other topological features the traveler must traverse. Incorporating these additional details would make the model too complex for easy use. Since models must be simple enough that you can use them to make predictions, they often leave out some of the details.
ALSO.
The conformation of molecules are based on probability. It fails to take into account the electronegativity of individual atoms. And it is ineffective in showing inorganic interactions with metals and such.
Each enzyme is comprised of covalently linked amino acids...enzymes are proteins
Skin prevents the body from getting infections