B1 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
• Orders of magnitude


  A way to understand how much bigger or smaller one object is compared to another
• Prefixes to show multiples of units

  • Centi (0.01)
  • Milli (0.001)
  • Micro (0.000,001)
  • Nano (0.000,000,001)
• 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
• Standard form


  A way to represent very large or small numbers by multiplying by a power of 10, with the 'number' between 1 and 10
• Culture medium


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

  Make suspension of bacteria, mix with sterile nutrient broth, stopper with cotton wool, shake regularly
• Growing microorganisms on agar plates

  Spread bacteria suspension on agar plate, seal, incubate, colonies form
• Culturing microorganisms


  • Microorganisms are very small, so scientists need to grow many of them in the lab using nutrients
• Components of culture medium

  • Carbohydrates for energy
  • Minerals
  • Proteins
  • Vitamins
• Growing microorganisms in the lab

  1. In nutrient broth solution

  2. On an agar gel plate
• Reasons for sterilisation


  To prevent contamination with other microorganisms that could compete for nutrients and space, or be harmful
• If bacteria have nutrients and suitable temperature

  They can multiply by binary fission as fast as every 20 minutes
• Formula to calculate number of bacteria

  Bacteria at beginning x 2^(number of divisions) = bacteria at end
• Bacteria can be used to test effects of antibiotics
• Steps for antibiotic effectiveness test

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

  2. Leave plate to incubate

  3. Measure size of inhibition zone
• Chromosomes


  Contain coils of DNA, with each chromosome carrying many genes
• Number of chromosomes


  23 pairs in body cells, 23 in gamete cells
• Cell cycle and mitosis

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

  2. Mitosis: chromosomes line up and separate

  3. Cytokinesis: two daughter cells form
• 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 that won't be rejected
• Benefits and problems of stem cell research

  • Benefits: Replace damaged/diseased parts, use unwanted embryos, research differentiation
  • Problems: Don't fully understand differentiation, ethical issues, risk of contamination, money/time better spent elsewhere
• Diffusion


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