cell biology

• Scaling prefixes


  Used to convert units and save from writing a lot of 0x
• Scaling prefixes


  • tera (T)
  • giga (G)
  • mega (M)
  • killo (k)
  • deci (d)
  • centi (c)
  • milli (m)
  • micro (μ)
  • nano (n)
• Conversion factor


  The number of times the smaller unit goes into the larger unit
• Converting units


  1. Multiply by conversion factor to go from bigger to smaller unit

  2. Divide by conversion factor to go from smaller to bigger unit
• Units to convert


  • Length: mm, μm, nm
  • Mass: kg, g
  • Volume: m³, dm³, cm³
  • Energy: J, kJ
• Organisms can be Prokaryotes or Eukaryotes
• Eukaryotic cells


  Complex, include all animal and plant cells
• Prokaryotic cells


  Smaller and simpler, e.g. bacteria
• Subcellular structures in animal cells


  • Nucleus
  • Mitochondria
  • Cytoplasm
  • Cell membrane
  • Ribosomes
• Additional subcellular structures in plant cells


  • Rigid cell wall
  • Chloroplasts
  • Permanent vacuole
• Bacterial cells


  • Don't have a 'true' nucleus, instead have a single circular strand of DNA
  • May contain small rings of DNA called plasmids
  • Don't have chloroplasts or mitochondria
• Magnification


  Image size / Real size
• Standard form


  Writing very big or small numbers with a decimal between 1 and 10, and a power of 10
• Preparing a slide


  1. Add water drop

  2. Add specimen

  3. Add stain

  4. Cover with cover slip
• Parts of a light microscope


  • Eyepiece
  • Coarse adjustment knob
  • Fine adjustment knob
  • Light
  • High and low power objective lenses
  • Stage
• Using a light microscope

  1. Clip slide onto stage

  2. Start with lowest power lens

  3. Use coarse adjustment to get in focus

  4. Use fine adjustment to get clear image

  5. Swap to higher power lens if needed
• Drawing microscope observations


  • Use pencil, take up at least half the space, clear unbroken lines, no colour or shading, draw subcellular structures in proportion, include title and magnification
• Cell differentiation


  Process by which a cell changes to become specialised for its job
• Examples of specialised cells


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


  • Undifferentiated cells that can differentiate into specialised cells
• Nerve cells


  • Have extensions at their ends to connect to other nerve cells and form a network throughout the body
• Cell Specialisation


  Muscle Cells are Specialised for Contraction
• Function of a muscle cell

  1. Contract quickly

  2. Be long (so they have space to contract)

  3. Contain lots of mitochondria to generate the energy needed for contraction
• Root Hair Cells


  • Cells on the surface of plant roots, which grow into long "hairs" that stick out into the soil
  • Gives the plant a big surface area for absorbing water and mineral ions from the soil
• Phloem and Xylem Cells


  • Form phloem and xylem tubes, which transport substances such as food and water around plants
  • Cells are long and joined end to end
  • Xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them
• Stem Cells


  Undifferentiated cells that can divide to produce more undifferentiated cells and differentiate into different types of cell depending on what instructions they're given
• Embryonic Stem Cells


  • Can turn into any type of cell
• Adult Stem Cells


  • Can only turn into certain cell types, such as blood cells
• Stem cell research


  1. Grow stem cells in a lab to produce clones and differentiate them into specialised cells for medicine or research

  2. Use stem cells to replace faulty cells in patients (e.g. insulin-producing cells for diabetes, nerve cells for spinal injuries)

  3. Therapeutic cloning to make an embryo with the same genetic information as the patient
• Arguments against stem cell research


  • Embryos are potential human lives and shouldn't be used for experiments
  • Curing existing patients is more important than the rights of embryos
  • Embryos used are often unwanted ones from fertility clinics that would be destroyed anyway
  • Scientists should focus on finding other sources of stem cells
• Plant stem cells


  • Found in the meristems (parts of the plant where growth occurs)
  • Can differentiate into any type of plant cell throughout the plant's life
  • Can be used to produce clones of whole plants quickly and cheaply
  • Can be used to grow crops of identical plants with desired features
• Chromosomes


  Coiled up lengths of DNA molecules that contain genes
• Cell Cycle


  Series of stages that body cells go through to divide and produce new cells for growth, development and repair
• Mitosis


  1. Cell grows and replicates its DNA

  2. Chromosomes line up and are pulled apart to opposite ends of the cell

  3. Membranes form around the sets of chromosomes to create the nuclei of the two new cells

  4. Cytoplasm and cell membrane divide to produce the two new daughter cells
• Diffusion


  The gradual movement of particles from an area of higher concentration to an area of lower concentration
• Cell membranes


  • Allow small dissolved substances like oxygen, glucose, amino acids and water to move in and out by diffusion
  • Don't allow large molecules like starch and proteins to pass through
• Osmosis


  The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• Observing osmosis in plant tissue


  1. Cut potato into cylinders

  2. Place in beakers with different sugar solutions

  3. Measure mass before and after to see if water has been gained or lost by osmosis
• Molde


  Concentration of 1 mol/dm³
• Other concentrations


  • 0.2 mol/dm³
  • 0.4 mol/dm³
  • 0.6 mol/dm³