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Introduction to cells


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Introduction to cells

  1. 1. Introduction to Cells
  2. 2. Cell Theory <ul><li>As we learned in the first week of school, having or being made of cells is one of the six basic requirements for life. </li></ul><ul><li>Even though it may seem common knowledge to us now, people didn’t always know that cells even existed. </li></ul><ul><li>It wasn’t until 1665 that Robert Hooke first described these building blocks of life, after examining dead cork tissue under a microscope. </li></ul><ul><li>Hooke called them cells because they reminded him of the rooms that monks lived in at a monastery. </li></ul><ul><li>Cells from Hooke’s Micrographia </li></ul>
  3. 3. Size Matters! <ul><li>While the majority of cells are too small to see with the naked eye, some are actually quite large. </li></ul><ul><li>For example, human egg cells are about the size of a grain of salt </li></ul><ul><li>Ostrich eggs are larger than baseballs! </li></ul>
  4. 4. Cell Theory (cont’d) <ul><li>Over the next 150 years, scientists solidified cell theory into the following three hypotheses: </li></ul><ul><ul><li>All living things are made up of one or more cells </li></ul></ul><ul><ul><li>Cells are the basic units of structure and function in an organism </li></ul></ul><ul><ul><li>Cells come only from the reproduction of existing cells </li></ul></ul>
  5. 5. Cell Size (cont’d) <ul><li>As stated earlier, the vast majority of cells are very small. </li></ul><ul><ul><li>Why do cells have to be so small? </li></ul></ul><ul><li>The reason cells are small boils down to the ratio of surface area to volume . </li></ul><ul><li>r=C/2 π SA= 4π r 2 V = (4/3) π r 3 </li></ul>
  6. 6. What Just Happened? <ul><li>As the balloon is more and more inflated, the volume of the air inside increases faster than the surface area of the elastic in the balloon. </li></ul><ul><li>Try to think of it in terms of how many more breaths you need to make the balloon look significantly bigger. </li></ul><ul><li>When the surface area to volume ratio is too low (or the volume to surface area ratio is too high), it’s difficult for the cell to get as many nutrients as it needs to support everything that makes up that volume, and then it dies. </li></ul>
  7. 7. What’s it Mean? <ul><li>Well, there are only so many available places where materials can pass either in or out of the cell through the membrane. </li></ul><ul><li>If the surface area to volume ratio is too low, it’s difficult for the cell to get as many nutrients as it needs to support everything that makes up that volume, and then it dies. </li></ul><ul><li>Bottom line: Large surface area to volume ratio good , small surface area to volume ratio bad ! </li></ul>
  8. 8. Shape Matters Too! <ul><li>Just like proteins and carbohydrates, the shape of a cell is directly tied to its function. </li></ul><ul><li>Nerve cells have long extensions that allow it to have a greater reach in the body and more efficiently transmit or receive impulses. </li></ul><ul><li>Red blood cells have their particular shape to have the largest surface area possible to carry and deliver the maximum amount of oxygen to other cells. </li></ul>
  9. 9. Organelles <ul><li>Just like how our bodies have specialized organs to carry out different functions necessary for life, individual cells have organelles , each carrying out a specific purpose. </li></ul>
  10. 10. Types of Cells <ul><li>Eukaryotes </li></ul><ul><li>Cell is surrounded by an outer cell membrane. </li></ul><ul><li>Has a nucleus , which is a membrane bound organelle that controls the cell and houses most of its genetic material. </li></ul><ul><li>Contains a wide array of membrane bound organelles that carry out many different functions </li></ul><ul><li>Prokaryotes </li></ul><ul><li>Cell is surrounded by an outer cell membrane. </li></ul><ul><li>Contains no nucleus. A prokaryote’s genetic material stays in the center of the cell, but there is no actual membrane surrounding it </li></ul><ul><li>Contains no membrane bound organelles </li></ul>