Cell Structure

• Prokaryotic cells have a cell wall
• Prokaryotic cells do not have a nucleus
• Genetic material in a prokaryotic cell

  A single DNA loop and a plasmid
• Common parts of animal and plant cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Further features of a plant cell

  • Chloroplasts
  • Permanent vacuole (filled with cell sap)
  • Cell wall
• Function of the nucleus


  Controls the activities of the cell and contains the genetic information of the cell
• Function of the cytoplasm


  The location of most chemical reactions
• Function of the cell membrane


  To control what is allowed into and out of the cell
• Function of the mitochondria

  Where aerobic respiration occurs to release energy
• Function of the ribosomes


  Protein synthesis (to make proteins by joining amino acids together)
• Function of the chloroplasts


  The location of photosynthesis
• Function of the permanent vacuole


  A storage area for cell sap, including ions and water, sometimes pigments
• Definition of a cell


  The individual unit of an organism
• Definition of a tissue


  Cells of the same type working together to perform a specific function
• Definition of an organ


  A structure made from multiple tissue types working together to perform a specific function
• Definition of an organ system


  Multiple organs working together to perform a specific function
• Sperm cell specialisation


  • Mobile due to flagellum; many mitochondria to allow high energy release for movement; streamlined head; digestive enzymes in head to break down egg membrane
• Nerve cell specialisation


  • Many mitochondria to provide lots of energy for active transport; many proteins embedded in cell membrane to allow ion movement; many branches to connect to other neurones
• Muscle cell specialisation


  • Many mitochondria to provide lots of energy for contraction; many ribosomes to synthesise proteins
• Root hair cell specialisation

  • Elongated shape to increase surface area for ion absorption; many mitochondria to provide lots of energy for active transport
• Xylem cell specialisation


  • Little cell contents to allow easy movement of water and ions through each cell
• Phloem cell specialisation


  • Needs a companion cell to work optimally; have sieve plates between cells to allow ease of transport of the sugar
• Cell differentiation


  The process of a stem cell dividing and becoming a specialised cell
• Animal cells differentiate at an early stage of development
• Plant cells retain the ability to differentiate throughout life
• Cell differentiation in mature animals

  Repair of tissues and replacement of old/damaged cells
• Advantages of electron microscopes over light microscopes

  • Increased magnification
  • Increased resolution
• What can be seen with an electron microscope

  Finer detail; more subcellular structures
• Resolution or resolving power of a microscope


  The ability to determine two close objects as separate images
• Magnification formula


  Magnification = Image size / Real size
• 1340000 nm expressed in standard form is 1.34 x 10^6 nm
• 0.0000001 µm expressed in standard form is 1 x 10^-7 µm
• The difference between mm, µm and nm is a factor of 1000
• Bacterial cell division process


  Binary fission
• Bacterial cells can divide around every 20 minutes if provided with enough nutrients and a suitable temperature
• Ways bacteria can be grown in a laboratory

  • In a nutrient broth solution
  • On an agar gel plate/petri dish
• Contaminant


  An unwanted species of microorganism growing in your culture
• Petri dishes and culture media should be sterilised at high temperature before use to kill contaminants
• Inoculating loops should be passed through a Bunsen burner flame before use to sterilise them and kill unwanted microbes
• Petri dishes should be stored upside down with tape securing the lid to stop drops of condensation falling on to the agar's surface and to stop unwanted microbes from the air entering