Chapter 4: cells j the working units of life. N cell theory has three important implications: studying cells is similar to studying life, life is continuous, origin of life marked by the origin of first cells. N cells are generally small (exceptions: eggs of birds and neurons) N as the cell increases in size, its chemical activity grows faster than the rate it can transfer molecules in and out j which results in waste build up. N also the cell must transfer materials from one end of the cell to another, smaller cells achieve this better. N things are grouped together via various factors: structure, organization, methods of acquiring energy, reproduction and gene sequence of cells www. notesolution. com. N bacteria: single-celled, lack double membrane bound organelles, have either no cell walls (gram negative) or a cell wall containing peptidoglycan (gram- positive) N archaea: single-celled organisms, lack double membrane bound organelles, have cell walls but none with peptidoglycan.