Cell Biology

• Chromosomes


  DNA molecules combined with proteins
• Chromosomes

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


  • Enables production of large numbers of disease-resistant plants
  • Produces two genetically identical cells
• Therapeutic Cloning


  Embryo cloned with the same genetic makeup as the patient → no rejection
• Stem Cells

  An unspecialised cell that is capable of differentiating into other cell types and of self-renewal
• Types of Stem Cells

  • Embryonic
  • Bone marrow
• 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
• Interphase


  Cell grows in size, synthesises new organelles
• Mitosis

  • DNA replicates
  • Separated to opposite poles of the cell
  • 2 sets of chromosomes
  • Cytoplasm Division
• Plant Cells


  Meristem Cells can differentiate into any kind of plant cell during the plant's life
• Animal Cells

  For growth and repair
• Treatment

  e.g. diabetes, paralysis
• Plant Meristem Cloning


  Protection of rare species from extinction
• Chromosomes carry genes
• Domains

  • Microscopy
  • Specialisation + Differentiation
• Light microscope


  Uses light to create an image
• Eukaryotes

  • Plants
  • Animals
• Prokaryotes


  No nucleus
• Magnification

  Number of times large the image appears compared to the size of the object
• Circular DNA


  Prokaryotes have circular DNA
• Plasmids


  Circular DNA found in prokaryotes
• Cell wall

  Plants have a cellulose cell wall
• Binary fission


  Prokaryotes reproduce by binary fission
• Chloroplasts


  • Contain chlorophyll for photosynthesis
• Ribosomes

  • Involved in protein synthesis
• Permanent vacuole


  • Stores cell sap and pigments
• Cell membrane

  Controls movement of substances in and out of cells
• Resolution


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


  Uses electron beam, observes greater detail
• Electron microscope has higher resolution than light microscope
• Plant cell types

  • Xylem cells
  • Phloem cells
• Animal cell types

  • Sperm cells
  • Nerve cells
• Cell differentiation in plants

  • Most differentiate at an early stage

  Many cell types can differentiate throughout a plant's life
• Aseptic techniques


  • Sterilise equipment by flaming

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

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

  Measure area of zone of inhibition
• Mitochondria


  • Involved in ATP synthesis
• 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, requiring energy from respiration