cell intro

• Cell


  The basic unit of life
• Every minute of the day we lose about 30,000 to 40,000 dead skin cells off the surface of our skin. So just in the time it took you to read this far, you've probably lost about 40,000 cells. That's almost 9 pounds (4 kilograms) of cells every year!
• 70-80 % home dust is our skin
• Lifespan of skin cells is about 2-3 weeks
• Two Dutch lens makers Hans and Zacharias Janssen invented the first compound microscope


  Around the year 1590

  
• English scientist Robert Hooke discovered and came up with the name "cells" while looking through a microscope at a piece of cork


  1665

  
• Cytology


  Study of cells
• Robert Hooke


  • English scientist
  • Used a microscope to examine cork (plant)
  • Called what he saw "Cells"

  
• Zacharias Janssen


  • Invented the telescope and/or the microscope

  
• Dutch scientist Anton Van Leeuwenhoek observed some of the first living cells under a simple (1 lens) microscope


  Not long after Hooke (around 1683)

  
• Animalcules


  Small organisms named by Van Leeuwenhoek, some of which were protozoa
• The discovery of cells would not have been possible without the invention of the microscope
• Compound light microscopes


  • Use glass lenses just like the early microscopes Robert Hooke used
  • Use electricity, a source of light, and can magnify images up to 1000x w/out blurring
• Modern microscopes


  • Transmission electron microscope (TEM) and scanning electron microscope (SEM) can magnify specimens up to 500,000x
  • Disadvantage is that the specimens must be dead
• Cells


  • Come in a variety of shapes and sizes, but all cells share some basic characteristics
  • One thing that all cells have in common is a plasma (cell) membrane
  • The cell membrane is a boundary which allows things into and out of the cell
• Eukaryotes


  Cells with a membrane-bound nucleus and membrane-bound organelles
• Prokaryotes


  Cells without a membrane-bound nucleus and membrane-bound organelles
• Nucleus


  The central organelle of a cell that contains the genetic material (DNA)
• Organelles


  Special structures that perform vital functions necessary to the cell
• Cell size


  • Female egg is the largest cell in the human body, visible without a microscope
  • Most cells are only visible with a microscope
  • Cells are small due to the ratio between their outer surface area and volume, and because the cell's nucleus can only control a certain amount of living, active cytoplasm
• Cell shape


  • Diversity of form reflects a diversity of function
  • The shape of a cell depends on its function
• Prokaryotic cell examples


  • Bacteria
  • Clostridium (genus with bacterial weapons that make them tough pathogens)
• Prokaryotes


  • Can be our friends (normal gut flora) or foes (pathogenic bacteria)
  • Bacteria are everywhere
• Eukaryotes


  • The "mansion" of cells, containing a nucleus and membrane-bound organelles
• Plant cells


  • Have a cell wall, chloroplasts, and large central vacuole
• Animal cells


  • Have centrioles, lysosomes, and no cell wall or chloroplasts
• Plasma membrane


  The boundary of the cell, composed of three distinct layers - two layers of fat and one layer of protein