B1 Cell biology

• Animals


  • Multicellular
  • Heterotrophs
  • Reproduce sexually
• Plants

  • Multicellular
  • Autotrophs (get energy from sun via photosynthesis)
  • Do not consume other organisms
• 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
• Aerobic respiration in mitochondria releases energy for cells
• Characteristics of living things (organisms)

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Acronym for characteristics of living things

  Mrs gran
• 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 between units of length

  1. Divide by 1,000 to convert to a larger unit

  2. Multiply by 1,000 to convert to a smaller unit
• 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
• 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
• 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 microscope

  Microscope that uses light, small, easy to use, relatively cheap
• Resolution of light microscope

  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 microscope

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

  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
• Comparing light and electron microscopes

  Electron microscopes have 2000 times better resolution than light microscopes
• You are often asked to compare the pros and cons of light and electron microscopes
• Diffusion


  The net movement of particles from an area of higher concentration to an area of lower concentration
• Diffusion


  1. Molecules move about randomly

  2. Molecules spread out over time

  3. Molecules become evenly distributed