What do you, an octopus and a large oak have in common????? All made up of cells about trillion actually Cell Division: Mitosis

I. Cells Divide A. The Cell Theory States: 1. Cells come from cells 1 cell becomes 2 cells that then become 4 cells ect. Increasing the amount of cells allows an organism to grow.

II. Limits to Cell Growth A. 2 main reasons why a cell divides rather than continue growing indefinitely 1. More demand placed on its DNA (muscle cells paramecium) 2. Surface area to volume ratio: in order to move enough nutrients & waste across the membrane cells need a lot of surface area

III. The Cell Cycle A. Cells grow & then wear out or get damage so they need to be replaced to form 2 new daughter cells this happens during the cell cycle. The cell cycle begins at one division and ends at the next. B. All cells go through a life cycle, the time for each cell varies. 1. Some embryo cells take up to 20 minutes 2. Skin cells go through cycle within seconds (at age 18 you have a whole new layer of skin every few weeks)

III. The Cell Cycle cont. C. Consists of 3 main parts: 1.Growth & Development (Interphase: G 1,S,G 2 ) DNA copies itself, Cell grows and prepares for division 2.Mitosis (P.M.A.T.) 3.Cytokinesis (Cytoplasm divides)

IV. Interphase ( between) A. Divided into 3 parts: 1. G 1 (gap/growth): growing stage increase in size & replicate proteins and organelles 2. S (synthesis): replication of chromosomes (DNA) Every cell needs all the DNA to carry out all life functions 3. G 2 : organelles & materials for cell division are produced B. All of these are regulated by check points and special proteins called cyclins & cyclin- dependent kinases (CDKs)

Checkpoints G 1 – checkpoint is known as restriction point (R) if it goes through this checkpoint cell will most likely divide if not cell will be arrested in G 0 phase. Cyclin-dependent kinases (CDKs) are activated by binding to the protein cyclin which exposes an active site of the CDK (allosteric regulation) Each different CDK has a specific cyclin protein to bind with. Cyclin is only produced at certain times. (can be synthesized by growth factors signals) Growth factor  Cyclin synthesis  CDK activation  Cell cycle events

V. Mitosis A. Mitosis: process during which the nucleus divides to form 2 identical nuclei. Involved with growth, repair & asexual reproduction. B. Steps of Mitosis: Prophase Metaphase Anaphase Telophase

VI. Steps of Mitosis A. Prophase (longest phase in M)- 1. Chromosomes (DNA) duplicate coil tightly into thickened strands called chromatids and the nucleus disintegrates. 2. Centrioles (made up of microtubules) move to opposite sides and form spindle fibers that will attach at the kinetochore which is part of the centromere

VI. Steps of Mitosis B. Metaphase- 1. The chromatids line up across the equatorial plane or metaphase plate of the cell 2. Centromeres (center of chromatids) at the kinetochore attached to spindle fibers

VI. Steps of Mitosis C. Anaphase- 1. The centromeres separate the 2 sister chromatids and move to opposite poles as microtubules continue pulling them apart. 2. Anaphase ends when the chromosomes stop moving 3. Non-kinetochore microtubules elongate cell

VI. Steps of Mitosis D. Telophase- 1. Spindle fibers start to disappear 2. Chromosomes uncoil and a new nucleolus & nuclear membrane form

VII. Division of Cytoplasm : Cytokinesis A. Cell membrane pinches in the middle and cytoplasm divides at the cleavage furrow. Creating 2 identical daughter cells. Contact inhibition or density dependent inhibition B. In Plant cells the appearance of a cell plate shows cytoplasm division as a cell wall begins to appear

IIX. Results of Cell Division A. Produces two new identical nuclei Both new cells have the same exact DNA, but they may not use all of the same DNA becoming two different types of cells

IX. Asexual Reproduction A. Asexual reproduction- new organism is produced from one parent. 1. The offspring will be identical to the parent (clone) 2. Examples: potatoes, strawberries, sunflowers

B. Budding & Regeneration Budding- new organism grows off already existing one Regeneration- whole body parts can grow back