Cell Biology

• Domains of cell structure

  • Microscopy
  • Specialisation
  • Differentiation
• Light microscope

  • Magnification
  • No nucleus
  • Circular DNA
  • Plasmids
  • Cell wall
  • Binary fission
  • Nuclear envelope present
• Plants

  • Nucleus
  • Eukaryotes
  • Cellulose cell wall
  • Chloroplasts
  • Golgi apparatus
  • Endoplasmic reticulum (Rough, Smooth)
  • Protein synthesis
  • Lipid synthesis
  • ATP synthesis
  • Ribosomes
  • No membrane-bound organelles
  • Permanent vacuole
  • Cell membrane
• Size of image / size of object

  • Resolution
  • Smallest distance between 2 points where they are seen as separate
• Electron microscope

  • Higher magnification
  • Uses electron beam
  • Observes greater detail
  • Limited by packaging and modification for transport
• Plants

  • Contain chlorophyll for photosynthesis
  • Stores cell sap and pigments
  • Controls movement of substances in and out of cells
• Animals

  • Xylem cells
  • Phloem cells
  • Sperm cells
  • Nerve cells
  • Most differentiate at an early stage
  • Many cell types can differentiate throughout a plant’s life
• Aseptic techniques

  1. Sterilise equipment by flaming

  2. Incubate at 25°C to prevent growth of bacteria pathogenic to humans

  3. Petri dish lid should be taped and placed upside-down
• To test the effectiveness of antibiotics

  1. Measure area of zone of inhibition

  2. Involved in protein synthesis

  3. Upside-down to prevent condensation disrupting culture
• Mitochondria

  • Involved in ATP synthesis
• Cell division


  Enables production of large numbers of disease-resistant plants
• Therapeutic cloning

  Produces two genetically identical cells for growth and repair
• Stem cells


  An unspecialised cell that is capable of differentiating into other cell types and of self-renewal
• Meristem cells


  Can differentiate into any kind of plant cell during the plant’s life
• Embryonic stem cells


  Can differentiate into most types of human cells
• Bone marrow stem cells


  Can differentiate into some types of cell e.g. blood cells
• Treatment

  Used for growth and repair e.g. diabetes, paralysis
• Chromosomes

  DNA molecules combined with proteins
• DNA


  A section of DNA which codes for a protein
• Humans have 46 chromosomes (23 pairs)
• Interphase


  Cell grows in size, synthesises new organelles
• Mitosis

  Chromosomes separate to opposite poles of the cell, producing two genetically identical cells
• Cytoplasm division

  Cell Cycle
• Cell division process

  • Interphase
  • Mitosis
  • Cytoplasm division
• Cell types

  • Plant cells
  • Animal cells
• Uses of stem cells

  • Therapeutic cloning
  • Protection of rare species from extinction
• Carry genes
• Diffusion


  Movement of molecules from a region of high concentration to a region of low concentration down their concentration gradient
• Osmosis


  Movement of water molecules from a region of high water potential to a region of low water potential down their water potential gradient
• Active Transport

  Movement of molecules from a low concentration to a high concentration against their concentration gradient
• Concentration gradient


  Difference in concentration of a substance between two regions
• Factors affecting rate of diffusion
• Temperature


  Affects the rate of diffusion by altering the kinetic energy of the particles
• Surface area

  Larger surface area increases the rate of diffusion
• Water potential

  Potential of water to move from one region to another
• Substances

  • Oxygen
  • Carbon dioxide
  • Urea
• Need for mass transport systems

  • Surface area: volume ratio too small
  • Adaptations
  • Requires energy from respiration
  • Passive
• Surface area: volume ratio too small


  As the size of a cell or organism increases, the surface area to volume ratio decreases, reducing the rate of diffusion
• Adaptations

  • Alveoli and cells of the small intestine have a large surface area
  • Thin cell walls of root cells give a short diffusion distance
  • Thin membrane gives a short diffusion path
• Placed in hypotonic solution

  Plant tissue placed in a solution where the water potential of the solution is higher than that of the plant tissue