Cell Biology

• Eukaryotes


  Animals and plants
• Animal cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
• Plant cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Sap vacuole
  • Chloroplast
• Prokaryotes


  Usually bacterial cells with no nucleus or subcellular structures with membranes
• Approximate sizes: Animal cell 10 micrometers, Plant cell 50 micrometers, Prokaryote 5 micrometers
• Nerve cell


  • Cell body
  • Dendrites
  • Axon
  • Insulating sheath
  • Axon terminals
• Sperm cell


  • Mid piece with mitochondria
  • Tail
  • Acrosome
• Muscle cell


  • Fibers for contraction
  • Mitochondria
  • Glycogen store
• Xylem cell


  • No end plates
  • No cytoplasm
  • Rings of lignin
• Phloem cell


  • Little cytoplasm
  • End plates with pores
  • Companion cells
• Root hair cell


  • Large surface area
  • Many mitochondria
• Microscopes


  Simple microscopes have low magnification and low resolving power

  Electron microscopes have high magnification and high resolving power
• Calculating magnification


  Magnification = Size of image / Size of real object
• Magnification calculations


  • Root hair cell image 5 mm, real size 20 μm, magnification 250x

  Sperm cell image 10 mm, magnification 2000x, real length 5 μm
• Culturing microorganisms


  Binary fission for rapid division

  Provide nutrients like glucose and amino acids

  Incubate at 25°C to encourage growth
• Growing uncontaminated cultures


  Sterilise equipment and work area

  Use inoculating loop to transfer bacteria to agar gel

  Seal petri dish to prevent contamination

  Incubate at 25°C
• Testing antibiotics/antiseptics


  Place antibiotic/antiseptic discs on agar with bacteria

  Measure area of dead bacteria around discs

  Control variables: disc area, concentration, volume
• Cell cycle and mitosis

  Stage 1: Cell growth and DNA replication

  Stage 2: Chromosomes line up and separate

  Stage 3: Cytoplasm and cell membrane divide
• Stem cells


  Undifferentiated cells that can develop into specialised cells
• Cell growth and division

  1. Cell grows and increases number of subcellular structures

  2. DNA replicates to form two copies of each chromosome

  3. Chromosomes line up along center and are pulled to each end of cell

  4. Cytoplasm and cell membranes divide to form two genetically identical cells
• Mitosis


  The process of cell division described above
• Embryonic stem cells


  Undifferentiated cells from the fertilized egg that can differentiate into most other cell types
• Adult stem cells


  Stem cells found in tissues like bone marrow that can differentiate into various cell types
• Plant stem cells


  Found in meristem tissue in root and shoot tips, can differentiate into any plant cell
• Therapeutic cloning


  Process of inserting a patient's body cell nucleus into an enucleated egg cell to produce stem cells for medical treatment
• Therapeutic cloning


  • Avoids rejection of tissues by patient
  • Potential to transfer viral infections
  • Some moral/religious objections
• Diffusion


  The spreading out of particles in a solution or gas, with a net movement from an area of higher concentration to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Active transport


  The movement of particles from an area of lower concentration to an area of higher concentration, requiring energy
• Active transport examples


  • Sugar absorption in small intestine
  • Mineral ion uptake in plant root hair cells
• Surface area to volume ratio

  Ratio of the surface area to the volume of an organism, decreases as organism size increases
• Adaptations for exchange in larger organisms

  • Villi and microvilli in small intestine
  • Alveoli in lungs
  • Stomata in leaves
  • Gill filaments in fish
• Osmosis


  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Investigating effect of solutions on plant tissue mass

  1. Prepare solutions of different concentrations

  2. Cut equal-sized plant tissue samples

  3. Immerse samples in solutions

  4. Measure mass before and after

  5. Calculate percent change in mass

  6. Plot results on graph
• Potato loses mass


  Solution outside is more concentrated than inside, so water moves out by osmosis
• Potato gains mass


  Solution inside is more concentrated than outside, so water moves in by osmosis