Cell Growth and Division Chapter 10 Cell Growth Does an adult have bigger cells than a child? Limits to Cell Growth Why do cells divide instead of continuing to grow? 1. DNA overload too much strain on DNA info to run cell. 2. Cell volume increases too rapidly for surface area (cell membrane). Inefficient material exchange. Too much stuff! Solution: Divide or Die! Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume in Cells Section 10-1 What is another reason, other than cell growth, that would cause cell division to occur? (Hint: when do we need to get new cells?) Some cells can readily divide, but some may rarely or never divide. Cell Division What is the necessary material for a new cell to have in order to function? What Are Chromosomes? Strands of DNA Every organism has a specific number of chromosomes. How many do humans cells have? Before cell division occurs, DNA must be copied so each new cell will have DNA instructions. Once copied, the two identical strands (or CHROMATIDS) are held together by a CENTROMERE. centromere Chromosome (uncopied) Chromosome (copied) chromatid s Draw this in your NB! Cell Cycle Life of a Cell Interphase growth period of cell, longest stage of cell life. 1. G 1 phase growth, more organelles 2. S phase DNA duplication 3. G 2 phase preparation for mitosis, last check Cell Division division of the cell into 2 1. Mitosis division of the nucleus 2. Cytokinesis division of the cytoplasm M phase G 2 phase S phase G 1 phase Section 10-2 Study this diagram! Pg. 245 in book Mitosis Prophase - Chromosomes become visible, centrioles move to opposite sides of cell (animal cells only), spindle forms, nuclear membrane breaks down Metaphase - Chromosomes line up in middle, spindle fibers attach to centromeres Anaphase - Sister chromatids are separated into individual chromosomes Telophase - chromosomes gather at opposite sides of cell, new nuclear membranes form Animal Cell Prophase Metaphase Telophase Anaphase Interphase Mitosis Animation Onion root tip active growing regionthis means lots of mitotic cells! Hint: If you see a NUCLEOLUS, it is in interphase. If you can see snake/fingerlike chromosomes, it is in a stage of mitosis. Prophase? Metaphase? Anaphase? Telophase? Cytokinesis Division of the cytoplasm This process starts during telophase In animal cells: cleavage of cell membrane. In plant cells: a cell plate forms midway between the divided nuclei. Cell Plate Forming Cleavage or Pinching in Cell Cycle and Cell Division Animation Animation #2 Question: Will the new cells have the same, more or less chromosomes than the mother cell? What happens if something goes wrong with the cell cycle? Cancer Uncontrolled cell division DNA is damaged by carcinogens or genetically inherited. Cell will not respond to cell cycle regulators. Carcinogens can be radiation, chemicals or viral Stem Cells Cell that have not become specialized. Stem cells can become any type of human cell. Abundant in embryos. Possible uses in science: treating nerve damage, growing organs, treating diseases.