Section 10-1 & 10-2

Learning Target: Know the reasons for why cells divide. Learning Outcome: I will know limitations to cell growth and structure of chromosomes.

Cells divide rather than get larger because……. 1. Demands on DNA would be too great. 2. Cell would have trouble moving food and waste across the cell membrane.

Volume increases faster than surface area.

 Each organism has a specific number of chromosomes.  During cell division chromatin condenses into chromosomes.  In order for each cell to get the right number the chromosomes have to double

 Therefore, since cells can not become too large they need to divide into “daughter cells”  To do this the DNA first copies itself so each daughter cell receives exact copies of the genetic info needed for the cell  Also the ratio of surface area to volume increases which is a very good thing!

Learning Target: Know the phases of mitosis. Learning Outcome: I will complete the “Mitosis Flipbook.”

 Cell cycle – The series of events that cells go through as they grow and divide.

 G1 – Growth phase #1. Cells increase in size and make new proteins and organelles.  S – Synthesis. Chromosomes are replicated.  G2 – Growth Phase #2 Cell division organelles are produced. Short phase.

Cell division is made up of 2 parts. 1. Mitosis – division of the nucleus. Divided into 4 phases. 2. Cytokinesis – division of the cytoplasm.

 Chromosomes are visible.  Centrioles separate  Spindle fibers form  Nuclear membrane breaks down.

 Chromosomes line up in the middle of the cell

 Chromosomes are pulled apart/away from each other.

 The opposite of prophase occurs.  Chromosomes disappear back to chromatin  Nuclear membrane reforms  Spindle fibers break apart and disappear

 Cytokinesis occurs right after Mitosis and is the division of the cytoplasm.