CELL GROWTH Do living things grow because it cells get larger and larger, or because they produce more and more cells? Because they produce more and more cells. LIMITS OF CELL GROWTH Surface area of a cell regulates the speed of exchange of water, oxygen, and food in a cell and wastes out of the cell. Cell volume regulates how quickly food and oxygen are used up and wasted are produced. See fig. 8-2: AS cell size increases, the volume increases faster than the surface area. This causes problems for the cell. Much like an office building. Materials have problems entering and leaving the cell.

LIMITS OF CELL GROWTH When the cell is small, DNA stored in the nucleus makes mRNA for proteins. As cell growth occurs mRNA increases. If the cell keeps growing, it can’t make enough mRNA and is inefficient, so cell division must occur. RATES OF CELL GROWTH Example is E.coli. Only takes 30 minutes if favorable conditions. CONTROLS OF CELL GROWTH Can be turned on and off as needed. Ex. Heart vs. skin Grow until they come in contact with other cells Growth can be stimulated for rapid or slow growth UNCONTROLLED CELL GROWTH Cancer: cells can’t control growth so they use up nutrients.