Cell Growth and the Cell Cycle Boy there are a lot of cycles: carbon cycle, ATP cycle, Calvin cycle, Krebs cycle…..

Cell Growth Recall that the cell membrane encloses the cell Cell size is limited due to the mathematical relationship between surface area and internal volume Volume increases as a cube function Surface area increases as a square function Why are small cells more efficient: recall the discussion on diffusion. Diffusion is faster over shorter distances

The math of it For a sphere: –area is 4  r 2 ; –volume is 4  /3 ( r 3 ) For a cube: –area is L(W) x 6; –volume is LWH

Cell Cycle Once cells reach a certain size they divide The cell cycle is a regular process of growing and dividing; the period of time between the beginning of one cell division to the beginning of the next cell division Thousands of events happen during the cell cycle but two are used as landmarks:

Cell Cycle There are four phases in the cell cycle Named with abbreviations for the phases: –G1 (first gap) most of the cells growth and activity in this phase –S (synthesis) cell duplicates its chromosomes –G2 (second gap) cell prepares for cell division –M (mitosis) cell divides

Cell Cycle One is cell division: cell divided into two independent cells (called daughter cells) –In eukaryotic cells this process is called mitosis Second landmark is the duplication of the chromosome

Thought experiment: Take a cube cell 1 um x 1 um x 1 um and double it to 2 um x 2 um x 2 um Calculate how the volume changes relative to the surface area.