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
• Bacteria are unicellular organisms, each individual cell is a whole organism
• 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
• Microscopy


  The use of microscopes
• How light microscopes work

  1. Light from the room hits the mirror

  2. Reflected upwards through the object

  3. Passes through the objective lens

  4. Passes through the eyepiece lens

  5. Into the eye
• Object

  The real object or sample that you're looking at
• 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
• Higher resolution

  More details can be seen, less blurry the image
• The images have the same magnification (100x) but different resolutions
• 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

  Really big, very expensive, hard to use, only used by scientists in laboratories
• Resolution of electron microscopes

  Maximum resolution of 0.1 nanometers, 2000 times better than light microscopes
• What electron microscopes can be used to study

  • Sub-cellular structures like mitochondria
• Electron microscopes can give images with much higher magnifications without going blurry
• Light microscopes

  Pros: small, easy to use, relatively cheap. Cons: limited resolution
• Electron microscopes

  Pros: very high resolution. Cons: big, expensive, hard to use
• 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
• Converting 6 millimeters

  • 6 millimeters = 0.006 meters = 0.000006 kilometers
  • 6 millimeters = 6,000 micrometers = 6,000,000 nanometers
• To convert between non-adjacent units, convert in steps
• • Naked eye can see down to 100 micrometers
  • Light microscope can see down to 500 nanometers
  • Electron microscope can see down to 0.1 nanometers
• Centimeters

  10 millimeters, 100 centimeters in a meter
• Converting centimeters

  1. To meters: divide by 100

  2. To millimeters: multiply by 10
• Converting 30 centimeters

  • 30 cm = 300 mm = 300,000 micrometers = 300,000,000 nanometers
• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development and repair
• The process through which these cells are generated is known as the cell cycle
• Cell cycle

  1. Growth

  2. DNA replication

  3. Mitosis and division (cytokinesis)
• DNA

  Usually spread out in long strings when cell is not dividing, condenses into chromosomes when cell starts to prepare for division