The Importance of Surface Area Size as a limiting factor • Within each cell there are a variety of molecules and organelles Size as a limiting factor • Cells are limited in size due to the surface area/volume ratio • The larger the cell the more energy it needs the higher the rate of metabolism • Higher metabolism increased fuel needs • However, due to increased size, the rate of diffusion is slower Size as a limiting factor • As cells increase in size, they become less efficient because the surface area/volume ratio decreases • There are not enough doorways to transport the needed amount of molecules into the cell • The molecules that enter the cell have too far to travel • Your cells can’t wait 2 hours for ATP, they need it now! Cell division • Cells divide when they become too large to effectively carry out metabolic functions • Smaller cells have the following advantages: • • • • Faster rate of diffusion & osmosis Adequate resources such as RNA Greater differentiation of jobs Faster travel (think sperm) SA/V ratio not just limited to cell size small intestine mitochondria brain Oooooh! Form fits function! Implications of the SA/V Factor • Keeping cells smaller, keeps the rate of diffusion fast Implications of the SA/V Factor • Limiting size helps cell carry out life functions efficiently • Cells can specialize • Characteristics are designed for specific functions • i.e. muscle cells with multiple mitochondria to carry out cellular respiration • Multicellular organisms can show emergent properties • Cells of the organism interact as a whole rather than individually • Multicellular organisms often have cells organized into tissues, organs, and organ systems. Any Questions??