Biology paper 1

• Animal cell structure


  Need to be able to label a basic animal cell and know what all the parts do
• 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 by containing cell sap
• Cell wall function


  Provide structural support, 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 (some)
  • Plasmids
  • Ribosomes
  • Chromosome (no nucleus)
• Flagellum function


  Used for moving/swimming
• Plasmid function


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


  Provides structure and protection, not made of cellulose
• Differences between prokaryotic and eukaryotic cells: no mitochondria/chloroplasts, no nucleus in prokaryotes
• Similarity between plant cells and prokaryotic cells: both have a cell wall
• Cells change size, shape and internal structures to carry out specific functions - specialized cells
• Examples of specialized plant cells

  • Root hair cells
  • Xylem
  • Phloem
• Root hair cell function

  Absorb water and mineral ions from the soil
• Xylem function


  Transport water
• Phloem function


  Transport sugars and amino acids
• Examples of specialized animal cells

  • Sperm cells
  • Nerve cells
  • Muscle cells
• Sperm cell function


  Swim to the egg
• Nerve cell function


  Transmit electrical impulses over long distances
• Muscle cell function


  Provide energy to contract
• Cell differentiation


  Process where different genes are turned on/off to specialize cells
• Stem cells


  Undifferentiated cells that can become specialized
• Plant cells can differentiate throughout life, animal cells mostly differentiate early and cannot change
• Microscopes magnify images to allow us to see smaller structures
• Optical/light microscope


  Uses light and lenses 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 (e.g. onion skin)

  3. Stain with iodine

  4. Lower coverslip

  5. Place on microscope stage

  6. Start at low power, focus, then increase magnification
• Binary fission


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

  1. Use sterile broth or agar plates

  2. Incubate at right temperature

  3. Prevent contamination using aseptic technique
• Antibiotic resistance testing


  Measure clear zones around antibiotic discs to determine resistance
• Chromosomes


  Coiled structures containing DNA, arranged in pairs