1. Cell Growth & Mitosis

2.  Cells grow until they reach their size limit. ◦ Stop growing ◦ Divide  What is the cell’s size limit? ◦ The ratio of it’s surface area to volume ◦ Surface area – area covered by plasma membrane ◦ Volume – space inside the cell  How does the amount of surface area change as the cell’s volume increases? *The ratio of surface area to volume decreases as the cell size increases.

3.  Movement of substances is easier in small cells ◦ Plasma membrane – selectively permeable ◦ Diffusion or motor proteins – slower over large distances  Cell size also affects ability of a cell to communicate instructions for cellular functions. ◦ Signals that trigger protein synthesis  Why might a high ratio of surface area to volume benefit a cell? ◦ It makes transporting nutrients easier & more efficient.

4.  Cells reproduce by a cycle of growing and dividing.  3 phases: Interphase, Mitosis, Cytokinesis  Interphase – Cell grows, carries out cell functions, and replicates copies of DNA  Mitosis – cell nucleus & nuclear material divide  Cytokinesis - cell’s cytoplasm divides, creating a new cell  Duration: 8 min – 1 year o normal cell cycle: 12-24 hours

5.  3 stages – G 1, S, G 2  G 1 – cell grows and performs normal functions  S – DNA is replicated ◦ Chromatin (relaxed DNA) condenses to form Chromosomes (contain genetic material passed from generation to generation)  G 2 – cell prepares for division of it’s nucleus

6.  The Cell Cycle is the method that eukaryotic cells used to reproduce.  Prokaryotic cells reproduce by binary fission. ◦ asexual reproduction by a separation of the body into two new bodies