<< Back to Lessons Index

# 6th Grade Science / Lesson 10 - Cell Size

 Cell Size What will we be learning today? In this lesson, we are going to learn all about what limits cell size.

 What Limits Cell Size? Cells in your body are growing all the time. How does this happen? Food molecules enter a cell through its membrane. A cell uses these substances to form new cell material. As a result it grows. Eventually it divides.

 As a cell grows, the space it takes up--or volume--increases much faster than its outer surface, the cell membrane. Cells cannot grow so large that their outer surface is too small to allow in enough needed materials and to allow wastes to be removed quickly enough. After reaching a certain size, the cell divides into two smaller cells.

 After a cell divides, substances that enter or leave the new cells have a greater cell surface area for moving in and out. The volume of the first cell is eight times larger than that of the second cell, just as the bigger cube has a volume eight times that of the small cube. Is the surface area of the bigger cell or cube eight times larger than that of the small cell or cube? Less than eight times larger? How does the surface area compare with the volume?

 While many cells in your body are growing and dividing, some are wearing out and dying. Worn-out cells on the surface of your skin peel off, such as cells on the palm of your hand. You may lose cells from a cut or scrape. In time cells divide and cover the cut with fresh skin.

 Let's Review What We Learned Today! Now complete your worksheet!