Cell Cycle & Mitosis Notes Essential What is the relationship of the process of mitosis to the growth of organisms and to Question: repair of damaged cellular materials? Activating Strategy: Quickwrite: when cells multiply they make more of themselves and also when cells divide they make more of themselves What are the 3 limits for cell size? 1. Diffusion-is the fast efficient over short distances but slow and inefficient over long distances. 2. DNA limits cell size-cells need A LOT of proteins to perform critical functions BUT there is a limit to how quickly DNA can be made into proteins. 3. Surface area to volume ratio-as a cells size increases, its volume increases much faster than its surface area. What are the reasons for cell division? a. maintaining optimum cell size b. growth in multicellular organisms c. asexual reproduction of single celled organisms d. to produce dead cells Chromatin vs. Chromosomes Chromatin is long strands of DNA wrapped around proteins Chromosomes coiled strands of DNA that look like X’s; becomes like this just before cell division. Cell Cycle During which phases does a cell spend most of its time? interphase During S the DNA is copied. Mitosis is the process in which a cells nucleus is divided into 2 new nuclei. Each new nuclei have the same kind and number of chromosomes as the parent. This is also called asexual reproduction. The cell cycle follows the following format. 1. Interphase (DNA replication) 2. Mitosis (which is broken into four phases) a. Prophase-nuc.env.dissappears chromosomes b. Metaphase-chromosomes (X’s) line up in the middle of the cell. Spindle fibers attach to the centromere on the chromosomes. Spindle fibers are produced by the centrioles c. Anaphase-spindle fibers begin to pull the chromosomes (X’s) apart. Chromatid (V’s) now move toward opposite ends d. Telophase- chromatid (V’s) reach the poles. Nuclear envelope begins to reappear around the chromatid. In plant cells a cell plate appears down in the middle to divide the cell. In the animal cells a cleavage furrow appears to separate the cell. Mitosis pictures: identify which is each phase: Anaphase Cytokinesis Chromatid Telophase 3. Cytokinesis- the production of 2 new identical daughter cells from the splitting of the cell’s cytoplasm. Mitosis Result is 2 identical daughter cells. It is how unicellular organisms reproduce. In multicellular organisms, cell growth and division results in a group of cells that work together. Cell → tissue → Organ → Organ System → ORGANISMS Cancer Enzyme control each phase of the cell cycle. Enzymes are proteins. Cancer is the result of uncontrolled cell growth. Extra mass of cells is called tumors. Causes of cancer are both genetic and enviromental( UV rays, smoke, and viral infections).