B1: Cell Biology

• Cells


  Organisms can be Prokaryotes or Eukaryotes
• Prokaryotes


  • Made of single cell
  • No true nucleus
• Eukaryotes


  • Made of cells with true nucleus
  • Membrane-bound organelles
• Plant and Animal Cells have Similarities and Differences
• Subcellular structures in cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  Contains genetic material that controls the activities of the cell
• Cytoplasm


  Gel-like substance where most of the chemical reactions happen
• Cell membrane


  Holds the cell together and controls what goes in and out
• Mitochondria


  Where cellular respiration takes place to transfer energy the cell needs
• Ribosomes


  Where proteins are made in the cell
• Additional structures in plant cells

  • Rigid cell wall
  • Permanent vacuole
  • Chloroplasts
• Cell wall


  Made of cellulose, supports and strengthens the cell
• Permanent vacuole


  Contains a weak solution of sugars and salts
• Chloroplasts


  Where photosynthesis occurs, contain chlorophyll to absorb light
• Bacterial Cells Are Much Smaller
• Bacterial cells


  • No true nucleus, have single circular DNA strand
  • May have plasmids
• Cells can be studied using microscopes
• Electron microscope


  Uses a beam of electrons instead of light to form an image, has higher resolution
• Resolution


  Ability to distinguish between two nearby objects
• Electron microscopes allow us to see much smaller things like viruses and plasmids
• Calculating magnification


  Image size / Real size
• Cells can be prepared for microscopy by staining and mounting on a slide
• Using a light microscope

  1. Place slide on stage

  2. Select low power objective

  3. Focus coarse adjustment

  4. Focus fine adjustment

  5. Switch to higher power objective
• Drawings of microscope observations should be neat, labelled, and proportional
• Cell differentiation is the process by which a cell becomes specialised for its function
• Most differentiated animal cells lose the ability to differentiate further, but plant cells often retain this ability
• Examples of specialised cells

  • Sperm cells
  • Nerve cells
  • Muscle cells
  • Root hair cells
  • Phloem and xylem cells
• Sperm cells


  • Long tail and streamlined head to swim to egg
  • Many mitochondria for energy
• Nerve cells


  • Long to cover distance, branched connections to form network
• Muscle cells


  • Long to contract, many mitochondria for energy
• Root hair cells


  • Long "hairs" to increase surface area for absorbing water and minerals
• Phloem and xylem cells


  • Long and joined end-to-end to form tubes for transporting substances
• Chromosomes contain the genetic information in the nucleus
• Chromosomes


  Coiled up lengths of DNA that carry genes
• Humans have 46 chromosomes, 23 pairs
• The cell cycle


  1. Growth and DNA replication

  2. Mitosis
• Mitosis


  The stage of the cell cycle when the cell divides
• Stages of mitosis


  1. Chromosomes line up

  2. Chromosomes pulled apart

  3. Nuclei form

  4. Cytoplasm divides
• Mitosis produces two genetically identical daughter cells
• Binary fission


  The process by which prokaryotic cells replicate