B1- cells

• Cells


  All life consists of cells
• Light microscope


  • Can see cells and maybe the nucleus
  • Cannot see subcellular structures
• Electron microscope


  • Allows us to see far finer details
  • Can see an image of the organelles
  • Has better resolving power and higher resolution
• Calculating cell size


  1. Measure the size of the image

  2. Divide by the magnification
• Cell types


  • Eukaryotic cells
  • Prokaryotic cells
• Eukaryotic cells


  • Have a nucleus where their DNA is found
  • Examples: plant and animal cells
• Prokaryotic cells


  • Don't have a nucleus
  • Their DNA is found in a ring called a plasmid
• Subcellular structures


  • Cell membrane
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plant cells)
  • Vacuole (in plant cells)
• Cell membrane


  • Keeps everything inside the cell
  • Semi-permeable, allows certain substances to pass through
• Cell wall


  • Extra structure found in plant cells and most bacteria
  • Made of cellulose
  • Provides a rigid structure
• Cytoplasm


  • Liquid that makes up the cell
  • Where most chemical reactions take place
• Mitochondria


  • Where respiration takes place
  • Releases energy for the cell to function
• Ribosomes


  Where proteins are assembled or synthesized
• Chloroplasts


  • Found in plant cells
  • Contain chlorophyll
  • Where photosynthesis takes place
• Vacuole


  • Found in plant cells
  • Permanent structure
  • Stores sap
• Bacterial multiplication


  1. Binary fission

  2. Number doubles every 10 minutes
• After 1 hour, 1 bacterium becomes 64 bacteria
• After 6 hours, 1 bacterium becomes 6.87 x 10^10 bacteria
• Practical on bacterial culture

  1. Use aseptic technique

  2. Lift lid towards flame to destroy other microbes

  3. Use sterilized equipment

  4. Put drop or spread culture

  5. Add antibiotic spots

  6. Hold lid on with tapers

  7. Incubate at 25°C
• Measuring bacterial culture


  1. Calculate size from initial drop or area where bacteria did not grow/were killed

  2. Use πr^2 or πd^2/4 to calculate area of circles
• Eukaryotic cell nuclei


  • Contain DNA
  • Stored in several chromosomes
  • Humans have 23 pairs (diploid cells)
• Gametes


  Have half the number of chromosomes (haploid cells)
• Cell division (mitosis)


  1. Genetic material is duplicated

  2. Number of ribosomes and mitochondria is doubled

  3. Nucleus breaks down

  4. One set of each chromosome pair is pulled to opposite sides

  5. New nuclei form in the two identical cells
• Cell specialization


  • Cells specialize depending on their function
  • Examples: nerve, muscle, root, xylem, phloem
• Stem cells


  • Haven't yet specialized
  • Found in human/animal embryos and plant meristem
  • Can specialize into blood cells
• Stem cells can be used to combat conditions like diabetes and paralysis
• Cloning plants can be used to prevent species from becoming extinct or produce crops with specific characteristics
• Diffusion


  • Movement of molecules/particles from high to low concentration
  • Down the concentration gradient
  • Passive process, doesn't require energy
• Osmosis


  Diffusion of water across a semi-permeable membrane
• If there is a higher concentration of glucose outside a cell


  Water moves out of the cell, resulting in a decrease in its mass
• Factors affecting rate of diffusion and osmosis

  • Increasing concentration difference
  • Increasing temperature
  • Increasing surface area
• Practical on osmosis


  1. Cut equal size cylinders from potato

  2. Weigh and place in test tubes with varying sugar solution concentrations

  3. After a day, remove, dab excess water, and reweigh

  4. Calculate percentage change in mass

  5. Plot percentages against concentration and find where line crosses x-axis (no change in mass)
• Active transport


  • Carrier proteins use energy to move substances through the membrane
  • Can move substances against a concentration gradient