Biochem Which elements are most common in living systems? 2. Of the necessary elements, which elements are non-metals? Which are metals? 3. What are the sources of elements for life? 4. List the major classes of biomolecules. 5. What is similar about some of these classes of biomolecules? What is different between them? 6. What features lead to class distinctions? 7. Describe the central dogma of biology. 8. Study the structure of cells. 9. What are the functions of membranes? How is a membrane like a ? (Create your own comparison.) 10. For organelles identify where are they found, the functions. Where are they not found?