Cell Size Limitation Notes

Cell Size limitations The cell theory (1838) states: The cell is the basic unit of life All living things are composed of cells All cells come from pre existing cells

Remember! Materials are moved in and out of cells through the process of diffusion: Diffusion is the tendency for particles of any kind to spread out spontaneously to regions where they are less concentrated Requires no energy

Cell Size Limitations Getting things into cell at an efficient rate Nutrients Water Oxygen Removing things from the cell quickly wastes DNA limits cell size If cell is too big then DNA cannot make enough proteins to support the cell

Cell Size Limitations Cells divide when the area of their cell membrane becomes too small to service the metabolic needs of the cell Cell size is limited by a surface to volume ratio As a cell gets larger, this ratio gets smaller, resulting in cell death because materials cannot diffuse across the cell membrane efficiently

Limits Lower limits of cell size: Upper limits to cell size: At a minimum, a cell must be large enough to house requires material (DNA, protein) to survive and reproduce Upper limits to cell size: The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of waste

Surface area to volume ratio limits size

What limits the size of cells? Surface Area to Volume Ratio - How much space is on the outside (cell membrane) compared to the space on the inside of the cell. As the surface area of something increases, it’s volume increases faster Surface area = L x W x # of sides (cm2) the surface of an object. The outside covering of a cell. (cell membrane) Volume = L x W x H (cm3) The space inside the cell A small object has a high surface area to volume ratio ex: 6/1 A large object has a small surface area to volume ratio ex: 24/8

It takes more time for the nutrients to reach the center of this cell Large Cell It takes more time for the nutrients to reach the center of this cell

Smaller cell It takes less time for the same nutrients to reach the center of this cell

Answers Not enough nutrients in fast enough As a cell gets larger which increases at a faster rate, the surface area or the volume? Volume If a cell were larger, would it’s interior structures be closer or further from the cell membrane? Further What problems might occur if cells were too large? Not enough nutrients in fast enough

Cell Size Limits Are whale cells the same size as starfish cells? Yes!

Conclusion As cell size increases, the surface area to volume ratio Decreases (small surface area to volume ratio), which can lead to death of a cell. Having a large surface area to volume ratio is important to the functioning of cells since it gets materials, nutrients, O2, & wastes into & out of it faster. Cells divide before they get too big!