Cell biology

• Cells


  Basic building blocks of life
• Cells


  Smallest unit of life that can replicate independently
• Bacteria cells


  A whole organism
• Kingdoms of life


  • Animals
  • Plants
  • Fungi
  • Protists
  • Bacteria
• Viruses are not actually living organisms
• Domains of life


  • Eukaryotes
  • Bacteria (Prokaryotes)
  • Viruses
• Eukaryotes


  Cells with a nucleus and membrane-bound organelles
• Prokaryotes


  Cells without a nucleus or membrane-bound organelles, 10-100x smaller than eukaryotes
• Animals


  • Multicellular
  • Heterotrophs - get energy from other organisms
  • Mostly reproduce sexually
• Types of organisms


  • Plants
  • Fungi
  • Protoctists (Protists)
  • Bacteria
  • Viruses
• Plants


  • Multicellular
  • Autotrophs - get energy from the sun (photosynthesis)
• Fungi


  • Mushrooms, mould - multicellular
  • Yeast - unicellular
  • Can't photosynthesise
  • Saprotrophs - most fungi feed using saprophytic nutrition
• Saprophytic nutrition of fungi

  1. Secrete digestive enzymes onto food outside their body

  2. Wait for the enzymes to break down the food

  3. Absorb all the nutrients back into their body
• Protoctists (Proties)


  • Nearly all unicellular
  • Some have chloroplasts (photosynthesize)
  • Amoeba - consume other organisms to get energy
• Bacteria


  • Unicellular
  • Some species can photosynthesise (none have chloroplasts)
  • Most feed off other organisms
• Viruses


  • Tiny particles, don't count as cells
  • Can only reproduce inside living cells
  • All viruses are pathogens
• Mitosis


  1. Cell growth

  2. DNA replication

  3. Cell division (cytokinesis)
• Cell cycle


  3 stages: growth, DNA replication & mitosis, division
• Cell growth


  • Cell grows in size and increases its number of sub cellular structures (mitochondria, )
• DNA replication


  • DNA is duplicated so each new cell will have a full set of DNA
• Cell division


  • Chromosomes line up in the centre, fibres attach and pull them to opposite sides, cytoplasm and cell membrane split to form 2 daughter cells
• Some bacteria can divide once every 20 minutes
• Bacterial cell divides every 30 minutes

  After 3 hours it would produce 64 cells
• Factors affecting bacterial growth


  • Temperature, nutrient availability, moisture, oxygen
• Nutrient broth and agar


  Nutrient-rich substances used to grow bacteria
• Bacterial colony


  Group of bacterial cells
• Aseptic techniques


  Cleaning surfaces, washing hands, sterilising equipment, creating sterile field
• Inoculation


  Transferring bacteria from a culture to an agar plate
• Investigating effects of antibiotics on bacterial growth using filter paper disks soaked in antiseptic solutions
• Stem cells


  Able to divide by mitosis to form more cells, able to differentiate into specialized cell types
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
• Embryonic stem cells


  • Can differentiate into any cell type
• Adult stem cells


  • Can only differentiate into certain cell types, used to replace damaged cells
• Risks of using stem cells include virus transmission and tumour development
• Ethical objection to embryonic stem cells is that they have the potential for human life
• Diffusion


  The net movement of particles from a high concentration to a low concentration
• Factors affecting rate of diffusion

  • Concentration gradient, temperature, surface area
• Osmosis


  The net movement of water molecules across a partially permeable membrane, from an area of higher water concentration to an area of lower water concentration
• Active transport


  Movement of molecules against their concentration gradient, requires energy from the cell
• Surface area to volume ratio


  • As organisms get larger, surface area to volume ratio decreases, making it harder to rely on diffusion alone