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

brain

small intestine

mitochondria

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??