cell biology

• Eukaryotes

  Cells that have a nucleus and membrane-bound organelles
• Prokaryotes

  Cells that lack a nucleus and membrane-bound organelles
• Components of animal and plant cells

  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Components of bacterial cells

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• Structures in animal and plant cells

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

  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Structures in bacterial cells

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single circular strand of DNA
  • Plasmids
• Cell specialisation

  The process where cells gain new sub-cellular structures to be suited to their role
• Specialised animal cells

  • Sperm cells
  • Nerve cells
  • Muscle cells
• Specialised plant cells

  • Root hair cells
  • Xylem cells
  • Phloem cells
• Cell differentiation

  The process where stem cells switch on/off genes to produce different proteins and acquire new sub-cellular structures
• In animals, most cells differentiate early and lose ability to differentiate, but some like red blood cells are replaced by adult stem cells
• In plants, many cell types retain ability to differentiate throughout life
• Light microscope

  Has two lenses (objective and eyepiece), illuminated from underneath, max magnification x2000, resolving power 200nm
• Electron microscope

  Uses electrons instead of light, two types (scanning and transmission), max magnification x2,000,000, resolving power 10nm (SEM) and 0.2nm (TEM)
• Calculating magnification of light microscope

  Magnification of eyepiece lens x magnification of objective lens
• Calculating size of object

  Size of image / magnification = size of object
• Culture medium

  Contains carbohydrates, minerals, proteins and vitamins to grow microorganisms
• Growing microorganisms in nutrient broth solution

  Make suspension of bacteria, mix with sterile nutrient broth, stopper with cotton wool, shake regularly
• Standard form

  Multiplying a certain number by a power of 10 to make it bigger or smaller, with the 'number' being between 1 and 10
• Culturing microorganisms

  Growing many microorganisms in the lab using nutrients
• Components of culture medium

  • Carbohydrates
  • Minerals
  • Proteins
  • Vitamins
• Growing microorganisms in nutrient broth

  1. Make suspension of bacteria

  2. Mix with sterile nutrient broth

  3. Stopper flask with cotton wool

  4. Shake regularly to provide oxygen
• Growing microorganisms on agar gel plate

  1. Pour hot sterilised agar jelly into sterilised Petri dish

  2. Allow to cool and set

  3. Inoculate with microorganism using sterilised loop

  4. Seal plate and incubate
• Reasons for sterilisation

  • Prevents contamination with other microorganisms
  • Prevents competition for nutrients and space
  • Prevents introduction of harmful microorganisms
• Reasons for sealing plate

  • Stops airborne microorganisms from contaminating
  • Allows oxygen to enter but prevents anaerobic bacteria
• Reasons for incubating at 25°C

  • Prevents growth of bacteria harmful to humans
• Bacteria can multiply by binary fission every 20 minutes
• Formula to calculate bacterial population growth

  Bacteria at beginning x 2^(number of divisions) = bacteria at end
• Testing antibiotic effectiveness

  1. Soak paper discs in antibiotics and place on agar plate with bacteria

  2. Leave plate to incubate

  3. Measure size of inhibition zone around discs
• Inhibition zone

  Clear area around antibiotic disc where bacteria have died
• Chromosomes

  Contain coils of DNA and carry genes
• Number of chromosomes

  46 in body cells, 23 in gametes
• Cell cycle and mitosis

  1. Interphase: cell growth, organelle increase, DNA replication

  2. Mitosis: chromosomes line up and separate

  3. Cytokinesis: cytoplasm and cell membrane divide to form two daughter cells
• Importance of mitosis

  • Growth and development
  • Replacing damaged cells
  • Asexual reproduction
• Stem cells

  Undifferentiated cells that can divide to produce more similar cells, some of which can differentiate
• Types of stem cells

  • Embryonic
  • Adult (e.g. in bone marrow)
  • Meristems in plants
• Therapeutic cloning

  Producing an embryo with the same genes as the patient to obtain stem cells for treatment
• Benefits and problems of stem cell research

  • Benefits: Replace damaged/diseased body parts, use unwanted embryos
  • Problems: Differentiation process not fully understood, ethical concerns, risk of contamination, money could be better spent
• Diffusion


  The spreading out of particles in a solution or gas, resulting in net movement from higher to lower concentration