Biology Topic 2

• Eukaryotic cells

  Cells that have a true nucleus and membrane-bound organelles
• 10 organelles to know in detail

  • Cell membrane
  • Rough endoplasmic reticulum
  • Golgi apparatus
  • Cytoplasm
  • Lysosomes
  • Mitochondria
  • Ribosomes
  • Vacuole
  • Chloroplasts
  • Cell wall
• Steps for each organelle

  1. Describe the structure

  2. Explain the function
• Cell membrane

  Single phospholipid bilayer with embedded proteins, cholesterol, and glycoproteins
• Cell membrane

  • Controls what can enter and exit the cell
  • Lipid-soluble substances can diffuse through, others need transport proteins
• Rough endoplasmic reticulum (rER)

  Folded membranes with ribosomes attached, site of protein synthesis
• Smooth endoplasmic reticulum (sER)

  Folded membranes without ribosomes, site of lipid and carbohydrate synthesis and storage
• Golgi apparatus

  Curved, folded membranes that process, package, and modify proteins into vesicles for transport
• Cytoplasm

  Jelly-like substance inside the cell where chemical reactions occur
• Lysosomes

  Membrane-bound sacs containing digestive enzymes that break down pathogens, dead cells, and other materials
• Mitochondria

  Double membrane organelle with inner folds (cristae), site of aerobic respiration and ATP production
• Ribosomes

  Small organelles made of proteins and rRNA where protein synthesis occurs
• Vacuoles

  Large, fluid-filled sacs in plant cells that provide structural support, store substances, and digest waste
• Chloroplasts

  Double membrane organelle with internal folded membranes (thylakoids), site of photosynthesis
• Cell wall

  Rigid structure outside the cell membrane in plants and fungi, provides structural support
• Cell walls are made of cellulose in plants and chitin in fungi
• Animal cells do not have cell walls
• The nucleus contains the genetic material (DNA) which controls all cellular activity
• Endoplasmic reticulum is involved in protein synthesis and transport
• Golgi apparatus modifies proteins and packages them into vesicles
• Magnification

  How many times larger the image that you look at is compared to the actual size of the object
• Resolution/Resolving power

  The minimum distance between two objects which they can still be viewed as separates
• Types of microscopes

  • Optical/light microscope
  • Transmission electron microscope
  • Scanning electron microscope
• Optical/light microscope


  • Uses a beam of light
  • Lower resolution
  • Lower magnification
  • Can view living samples
  • Produces color images
• Electron microscopes

  • Uses a beam of electrons
  • Higher resolution
  • Higher magnification
  • Cannot view living samples
  • Produces black and white images
• Optical microscopes cannot see the inside of organelles in detail and some small organelles cannot be seen at all
• Electron microscopes require the sample to be in a vacuum
• Transmission electron microscope

  Beam of electrons passes through the specimen
• Cell fractionation is a technique used to break open cells so you can then isolate the different organelles and examine their structure and function
• Cell fractionation

  1. Homogenization

  2. Ultracentrifugation
• Scanning electron microscope

  Beam of electrons scatters and reflects off the surface of the specimen
• Homogenization

  The process of breaking open or homogenizing the cells
• Ultracentrifugation

  The process of separating the organelles in the filtrate according to their density
• The solution the cells and organelles are prepared in must be cold, isotonic, and buffered
• Converting units

  Millimeters to micrometers: multiply by 1000

  Micrometers to millimeters: divide by 1000
• Calibrating the eyepiece graticule

  Place stage micrometer on stage

  Line up eyepiece graticule with stage micrometer

  Count how many eyepiece graticule divisions fit into one stage micrometer division

  Use this ratio to determine the value of one eyepiece graticule division
• Cold solution

  • Reduces enzyme activity to prevent damage to organelles
• Isotonic solution


  • Prevents osmosis and organelles from shriveling or bursting
• Buffered solution


  • Prevents sudden changes in pH that could damage organelles
• The actual size of a structure remains the same at different magnifications, only the value of one eyepiece graticule division changes