Cell Biology

• Cells

  The basic building blocks of life that can replicate independently
• Multicellular organisms like animals and plants contain many cells that divide to grow or replace dead cells, not to create new organisms</b>
• Bacteria are single-celled prokaryotic organisms
• Subcellular structures common to animal and plant cells

  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Plant cells

  • Have a rigid cell wall made of cellulose
  • Contain a permanent vacuole with cell sap
  • Contain chloroplasts for photosynthesis
• Bacterial cells

  • Lack mitochondria and chloroplasts
  • Have a single circular strand of DNA instead of a nucleus
  • May have additional plasmids
  • May have flagella for movement
• Photosynthesis occurs in the chloroplasts of plant cells, using chlorophyll to absorb light energy
• Mitochondria in cells break down glucose through aerobic respiration to provide energy
• Animals

  • Multicellular
  • Heterotrophs
  • Reproduce sexually
  • Estimated 5-10 million species
• Plants

  • Multicellular
  • Autotrophs (get energy from sun via photosynthesis)
  • Estimated 300,000 species
• Fungi

  • Some are multicellular, some are unicellular
  • Heterotrophs (get energy from other organisms)
  • Many use saprotrophic nutrition (secrete digestive enzymes outside body)
  • Some have a mycelium body made of hyphae
• Protists

  • Nearly all are unicellular
  • Some are plant-like (have chloroplasts, photosynthesize)
  • Some are animal-like (consume other organisms)
  • Some are pathogens that can cause disease
• Bacteria

  • Single-celled organisms
  • Some can photosynthesize but don't have chloroplasts
  • Most feed off other living or dead organisms
  • Estimated to have more species than all other kingdoms combined
  • Some are pathogens that can cause disease, but most are harmless or helpful
• Viruses

  • Tiny particles, not cells
  • Have a protein coat surrounding genetic material (DNA or RNA)
  • Can only reproduce by infecting and using other living cells
  • All are considered pathogens as they cause harm to host organisms
• Viruses, bacteria, protists, fungi, plants, and animals are the 6 groups of life, with viruses being the only non-living group
• Animals, plants, fungi, and protists are all eukaryotic organisms, while bacteria are prokaryotic
• Eukaryotic cells have DNA in chromosomes and a nucleus, while prokaryotic cells have loose DNA and no nucleus
• Viruses are 10-100 times smaller than prokaryotic cells
• Microscopy

  The use of microscopes
• How light microscopes work

  1. Light from the room hits the mirror

  2. Light reflected upwards through the object

  3. Light passes through the objective lens

  4. Light passes through the eyepiece lens

  5. Light enters the eye
• Image

  The image that we see when we look down the microscope
• Magnification

  How many times larger the image is than the object
• Magnification = image size / object size
• Resolution

  The shortest distance between two points on an object that can still be distinguished as two separate entities
• Light microscopes

  Microscopes that use light, small, easy to use, relatively cheap
• Resolution of light microscopes

  Limited to 0.2 micrometers, any details less than 0.2 micrometers apart will appear blurry
• What light microscopes can be used to see

  • Individual cells like onion cells
• Electron microscopes can give images with much higher magnifications without going blurry
• Nanometers

  Smallest unit of length you need to know
• Units of length

  • Nanometers
  • Micrometers
  • Millimeters
  • Meters
  • Kilometers
• Each unit is 1,000 times bigger or smaller than the one next to it
• Glucose molecules are about 1 nanometer across
• Viruses are about 100 nanometers across
• Animal and plant cells are 10 to 100 micrometers across
• Human hair is about 100 micrometers wide
• The naked eye can see down to about 100 micrometers
• Light microscopes can see down to about 500 nanometers
• Electron microscopes can see down to about 0.1 nanometers
• Centimeters


  10 millimeters, 100 centimeters in a meter
• Converting centimeters

  1. Divide by 100 to get meters

  2. Multiply by 10 to get millimeters