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Transcript
Cell Growth and Reproduction Cell Size Limitations Cell Size Limitations Although it is the smallest unit of life, a cell still has all of the characteristics of life. A cell is able to grow, but it is limited in how big it can grow because of the necessary functions it carries out…Remember organelles??? Cell Size Limitations The plasma membrane lets nutrients into the cell and allows wastes to leave. Inside the cell, nutrients and wastes move by diffusion. Diffusion limits cell size because it is a fast and efficient process only over short distances. Cell Size Limitations Remember, a cell has a lot of cell parts or organelles to perform specialized functions. In order for them to work together quickly and efficiently, they need to be able to transport things VERY QUICKLY therefore they have to be VERY small. Let’s take a look at our example… Cell Size Limitations Cell Size Limitations Because a cell’s size can slow down the rate of diffusion, cells have to have a way of limiting their growth. Cells divide before they become too big and therefore unable to function well: The cell would either starve to death or be poisoned from the buildup of waste products. Why Divide??? Cells divide in organisms for: 1. 2. 3. Cell repair Cell replacement Growth (lengthening of bones, etc) Cell Reproduction When cells divide, two new cells are produced from one cell. Remember the cell theory? Part 3 of the cell theory stated that all cells come from pre-existing cells. Cell Reproduction - Cell Reproduction, or cell division is the process by which new cells are produced from one cell. - Cell division results in two cells that are identical to the original, called a parent cell. The two new cells are called the daughter cells. When exact copies are made of “body” (not sperm or egg) cells, this is called MITOSIS. Cell Reproduction-Important Structures Organisms could not grow or function properly if the genetic material encoded in DNA was not passed from cell to cell. So when cells reproduce by dividing, they also pass along their DNA. But how??? Cell Reproduction-Important Structures Chromosome: the carrier of the genetic material that is copied and passed from generation to generation of cells; formed during cell division, it is only seen right before and right after cell division. *It has to be accurate (mistakes = mutations) *It is a rod-shaped structure made of tightly coiled DNA and protein Cell Reproduction-Important Structures Chromatin: long strands of DNA coiled in a ball in the nucleus for most of a cell’s lifetime, chromosomes are found in this form (looks like Ramen Noodles) Cell Reproduction-Important Structures Chromatid: half of the chromosome (individual sides). each part is called a sister chromatid Cell Reproduction-Important Structures Centromere: a part of the chromosome that holds sister chromatids together; helps move the chromosome during cell division Centromere Sister chromatids Chromosome Supercoil within chromosome Continued coiling within supercoil Histone DNA Cell Reproduction-Important Structures Chromosome centromere sister chromatids The Cell Cycle (in Eukaryotes) The cell cycle is the sequence of growth and division of a cell. Cell division is ONE stage. A cell will divide many times in its lifetime before it dies and is replaced by a new cell. There are three stages of the cell cycle: 1. The time BETWEEN cell divisions is called interphase. 2. The time OF cell division is called mitosis. 3. When the cytoplasm divides and you officially have 2 new cells, it is called cytokinesis. The Cell Cycle Growth Division 2 New Cells The Cell Cycle (in Eukaryotes) IPeedMadlyAtTheCrapper- Interphase Prophase Metaphase Anaphase Telophase Cytokinesis The cell cycle and Mitosis (in Eukaryotes) Cell division occurs in a series of stages, or phases. The cell cycle and Mitosis (in Eukaryotes) 1st: Interphase Copied Chromatin Sister chromosome Centromere ***Interphase is the longest and busiest phase of the cell cycle. Why do you think chromosomes are copied before cell division happens? The cell cycle and Mitosis (in Eukaryotes) 2nd: Prophase Mitosis Centrioles Spindle fibers: pull apart the sister chromatids. spindle fibers What happens: Chromatin condenses to form chromosomes so this is where chromosomes appear. The cell cycle and Mitosis (in Eukaryotes) 3rd: Metaphase spindles Chromatids What happens: The chromosomes line up in the middle of the cell. The cell cycle and Mitosis (in Eukaryotes) 4th: Anaphase Separate Opposite What happens: Centromeres split and sister chromatids are pulled apart to the opposite sides of the cell. The cell cycle and Mitosis (in Eukaryotes) 5th: Telophase Nuclei Threads Rods Mitosis What happens: Two new nuclei are formed and a double membrane begins to form around them. The cell cycle and Mitosis (in Eukaryotes) 6th: Cytokinesis Daughter Nucleus Chromosomes What happens: The cell’s cytoplasm divides and separates into two new identical cells. Mitosis in a Plant & Animal Cell CELL PLATE CLEAVAGE The Results of Mitosis = Organization Cells working together for the same function are called tissues Similar tissues will form an organ Several organs working together make up an organ system The results of mitosis: Cancer • Cancer is cell reproduction gone wrong: - It occurs when a cell loses control of its division and starts making cells even if they are not needed • Cancer can be caused by 3 major things: 1. UV radiation & radiation (too much sun, radiation exposure) 2. Environmental influences (ex. air pollution, smoking) 3. Viruses (a viral infection can damage genes) Cancer Prevention • Diets low in fat and high in fiber • Daily exercise • Not using tobacco Question 1 The structures in the cell nucleus that contain DNA are __________. A. centromeres B. chromosomes C. genes D. chlorophylls Question 2 Look at the diagram and identify the stage of mitosis that is depicted. Centromere Sister chromatids A. prophase C. anaphase B. metaphase D. telophase Question 3 What is the process by which a cell's cytoplasm divides? A. cytokinesis B. telekinesis C. meiosis D. mitosis Question 4 What is the name of the object that glues/holds sister chromatids together? A. centrioles B. centromeres C. tissues D. cell cycles Question 5 Magnification of a plant cell reveals centromeres that have split and sister chromatids being pulled to opposite poles of the cell. This cell is in which phase of mitosis? A. prophase B. metaphase C. anaphase D. telophase Question 6 Which phase of mitosis is depicted in this diagram? Spindle Fibers Doubled chromosome Disappearing nuclear envelope A. prophase C. anaphase B. metaphase D. telophase Question 7 What is the term used for the period of the cell cycle represented by the red arrow in this graph? A. prophase B. metaphase C. centrophase D. interphase DNA synthesis and replication Centrioles replicate; cell prepares for division Rapid growth and metabolic activity Mitosis Cytokinesis Question 8 What phase of mitosis is shown in this picture? A. Prophase B. Metaphase C. Interphase D. Telophase Question 9 What process is being represented by the blue arrow? (the pinching in of the cell membrane) A. Pinching B. Cleavage C. Cell Plate D. Cheeking Question 10 • What is the sentence we say to remember the phases in order? Please write out the sentence and place the correct phase next to it. Cancer…. • Please write 2 paragraphs on anything about cancer that interest you. – What causes it? – Treatments? – Types? – Etc….