How does your skin repair itself when you get a cut?

Why do cells divide? 1.) Growing organisms need more cells – What would happen if your cells stopped dividing? – Skin cells…what would happen if your skin cells stopped dividing?

2.) To replace damaged or worn out cells – Bloody knee – Peeling skin after a sunburn

3.) As cells grow, their volume is far too big for their surface area, and they can’t get nutrients in and waste out fast enough

What is the goal of cell division? To produce two identical cells called daughter cells. PARENT CELL TWO IDENTICAL DAUGHTER CELLS

The Cell Cycle 2 Major Phases of Cell Division 1.) Interphase G 1 Stage – primary growth phase S Stage- synthesis; DNA replication G 2 Stage – secondary growth phase 2.) Cell division (M-Phase) M – Mitosis C - Cytokinesis

Interphase – G 1 Stage 1 st stage after cell division Cells mature by making more cytoplasm and organelles Cell carries on its normal, everyday metabolic activities *This is the longest stage of the cell cycle

Interphase – S Stage Synthesis stage DNA is copied or replicated -Two identical copies of DNA - Each new cell is identical to the parent cell PARENT DNA *Why is it important that each new cell is IDENTICAL to the parent cell?

Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules PARENT DNA DNA replication occurs in S stage in the parent cell

Interphase – G 2 Stage 2nd Growth Stage Occurs after DNA has been copied All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized Everything must be in order for the cell to divide **Critical Checkpoint

Cell Division M-Phase (Mitosis and Cytokinesis) Mitosis (division of the nucleus) – Divided into 4 stages – 1.)Prophase – 2.)Metaphase – 3.)Anaphase – 4.)Telophase Cytokinesis evenly divides the cytoplasm

So how does your skin repair itself when you get a cut? Cellular division! When you cut your skin, the cells at the edge of the injury are stimulated to divide rapidly....interphase begins!

Cells where mitosis occurs in YOUR body Lifespan life span = 2 weeks life span = 4 months life span = days life span = 4-5 days Cell Type -Skin Cell -Red Blood Cell -Liver Cell -Internal linings (Intestines)

In your groups discuss… 1.) How do cancer cells grow? 2.) How does chemotherapy fight cancer (and what cause negative side effects?)

behave-differently-from-healthy-ones-george- zaidan