cell biology

• Eukaryotes


  Contain their genetic material enclosed in a nucleus
• Prokaryotes


  Genetic material is not enclosed in a nucleus
• Prokaryotic cells


  • Bacterial cells
  • Much smaller than eukaryotic cells
  • Contain cell wall
  • Contain cytoplasm
  • Contain plasmid
  • Contain loop of DNA
• Order of magnitude


  Every order of magnitude is 10x greater than the one before
• To find the order of magnitude, count the number of zeros
• 100x = 2 orders of magnitude
• Animal cells

  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Specialisation
• Plant cells


  • Regular shape
  • Chloroplasts
  • Cell wall
  • Vacuole
  • Cell membrane
• Adaptations of animal cells


  • Sperm cell
  • Nerve cell
• Adaptations of plant cells

  • Root hair cell
  • Muscle cell
  • Xylem cell
  • Phloem cell
• Using an optical microscope


  1. Place slide on stage

  2. Use lowest power objective lens

  3. Slowly turn coarse focusing dial

  4. Look through eyepiece

  5. Use fine focusing dial
• Magnification


  Multiply magnification of eyepiece lens by magnification of objective lens
• Electron microscopes


  • Much greater magnification
  • Much higher resolution than light microscopes
• Binary fission


  Bacterial cell splits into two bacterial cells
• Bacteria can carry out binary fission once every 20 minutes with enough nutrients and suitable temperature</b>
• Culturing microorganisms


  1. Use agar to grow bacteria

  2. Incubate at 25°C to prevent growth of harmful bacteria
• Investigating effect of antibiotics on bacteria


  1. Clean bench with disinfectant

  2. Flame inoculating loop

  3. Spread bacteria on agar plate

  4. Place antibiotic discs on plate

  5. Incubate at 25°C
• Inhibition zone


  Region around antibiotic disc where bacteria don't grow
• Chromosomes


  Made of DNA, carry genes that determine features
• Cell cycle (mitosis)


  • DNA replicates
  • Cell grows and divides nucleus
  • Cytoplasm and cell membrane divide
• Functions of mitosis


  • Growth and development
  • Repair
  • Asexual reproduction
• Stem cells


  Undifferentiated cells that can divide and differentiate into other cell types
• Adult stem cells can only differentiate into certain cell types, not any cell type
• Mitosis stage 1


  Growth
• Mitosis stage 2


  1. Chromosomes pulled to each end

  2. Nucleus divides
• Mitosis stage 3


  Cytoplasm and cell membrane divide to form 2 identical daughter cells
• Mitosis


  • Essential for growth and development of multicellular organisms
  • Takes place when an organism repairs itself
  • Happens during asexual reproduction
• Stem cells


  Undifferentiated cells which can divide into more cells of the same type and can differentiate to form other types of cells
• Fertilisation


  Sperm cell joins with egg cell
• Embryo formation


  1. Fertilised egg undergoes mitosis to form a ball of cells

  2. Cells begin to differentiate and form specialised cells
• Bone marrow transplant


  1. Patient's existing bone marrow is destroyed using radiation

  2. Patient receives transplant of bone marrow from a donor

  3. Stem cells in donated bone marrow divide and form new bone marrow

  4. Stem cells differentiate and form blood cells
• Donor must be compatible


  Otherwise, white blood cells produced by donated bone marrow could attack patient's body
• Bone marrow transplant


  Risk of viruses being passed from donor to patient
• Embryonic stem cell treatment


  1. Embryo is produced with the same genes as the patient

  2. Stem cells from the embryo can be used to treat the patient without being rejected by the immune system

  3. Once the stem cells are in the patient, they can continue to produce cells that have stopped working correctly

  4. This technique could be useful for several medical conditions like Parkinson's, diabetes, etc.
• Meristem tissue can be used to quickly and cheaply grow a large number of plants from a small sample
• Diffusion


  The spreading out of particles from an area of higher concentration to an area of lower concentration
• Oxygen concentration is higher outside the cell


  Oxygen moves into the cell by diffusion
• Carbon dioxide concentration is higher inside the cell


  Carbon dioxide moves out of the cell by diffusion
• Urea is a waste product produced inside cells


  Urea diffuses out of the cells into the blood plasma and is excreted by the kidneys
• Factors affecting rate of diffusion


  • Concentration gradient (greater gradient = faster diffusion)
  • Temperature (higher temperature = faster diffusion)
  • Surface area (larger surface area = faster diffusion)