biology paper 1

• Parts of an animal cell

  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Nucleus
  • Mitochondria
• Cell membrane function

  Control the entry and exit of substances into the cell
• Cytoplasm function

  Where chemical reactions happen inside the cell
• Ribosome function

  Protein synthesis - make proteins
• Nucleus function

  Control the cell activities
• Mitochondria function

  Where aerobic respiration happens to provide energy for the cell
• Plant cells also have a nucleus, ribosomes, and mitochondria
• Additional parts of a plant cell

  • Chloroplasts
  • Vacuole
  • Cell wall
  • Cell membrane
• Chloroplast function

  Absorb light energy for photosynthesis
• Vacuole function

  Support the cell structure
• Cell wall function

  Provide strength, made of cellulose
• Both animal and plant cells are classified as eukaryotic cells - have a nucleus
• Prokaryotic cells

  Cells without a nucleus, e.g. bacteria
• Parts of a bacterial cell

  • Cell membrane
  • Cytoplasm
  • Flagellum
  • Plasmids
  • Ribosomes
  • Chromosome
• Flagellum function

  For moving/swimming
• Plasmids

  Small loops of DNA that can contain useful genes like antibiotic resistance
• Bacterial cell wall

  For structure and protection, not made of cellulose
• Differences between prokaryotic and eukaryotic cells: no mitochondria/chloroplasts, no nucleus in prokaryotes
• Cells can be specialized to carry out specific functions
• Plant specialized cells


  • Root hair cells
  • Xylem
  • Phloem
• Cell differentiation


  Process where cells become specialized by turning different genes on/off
• Plant cells can differentiate throughout life, animal cells mostly differentiate early and then just divide by mitosis
• Microscopes magnify images to allow us to see small structures
• Optical/light microscope

  Uses lenses and light to magnify, can see nucleus and mitochondria
• Electron microscope


  Higher magnification and resolution, can see smaller structures like ribosomes
• Preparing a microscope slide

  1. Add drop of water

  2. Add thin piece of tissue

  3. Stain with iodine

  4. Lower coverslip

  5. Place on microscope stage

  6. Start at low power and focus

  7. Increase magnification
• Binary fission


  Rapid division of bacteria, can double every 20 minutes
• Growing bacteria in culture

  1. Use sterile technique

  2. Provide nutrients and oxygen

  3. Incubate at right temperature

  4. Observe colony growth and measure antibiotic resistance
• Chromosomes


  Coiled structures containing DNA, arranged in pairs
• Cell cycle


  Process of cell division, including interphase and mitosis
• Stem cells


  Undifferentiated cells that can become different cell types
• Types of stem cells

  • Embryonic
  • Adult
  • Plant meristems
• Therapeutic cloning

  Using stem cells genetically identical to patient to grow replacement cells
• Ethical issues around using embryonic stem cells
• Diffusion


  Net movement of particles from high to low concentration until evenly spread
• Stem cells

  Cells that can be grown into different types of cells, e.g. blood cells, nerve cells, pancreatic cells
• There are some ethical issues around using embryonic stem cells as the embryo cannot consent, and some view embryos as potential life
• There is a risk of viral infection or cancer when using stem cells, as they can divide rapidly
• Diffusion

  The net movement of particles from an area of high concentration to an area of low concentration, a passive process that does not require energy
• Substances that diffuse into and out of cells

  • Oxygen
  • Glucose
  • Carbon dioxide
  • Urea