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


  Used for moving/swimming
• Plasmids


  Small extra loops of DNA that often 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 change size, shape and internal structures to carry out specific functions - these are 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
• Muscle cell function


  Provide energy to contract
• Cell differentiation


  Process where different genes are turned on/off to change cell shape and structures
• Stem cells


  Undifferentiated cells that can differentiate into specialized cells
• Plant cells can differentiate throughout their life, animal cells mostly differentiate early and can't change
• Microscopes magnify images to allow us to see small 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

  3. Stain with iodine

  4. Lower cover slip

  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 broth or agar plates

  2. Incubate at right temperature

  3. Prevent contamination with aseptic technique
• Observing bacterial growth


  Look for clear zones around antibiotic discs to measure antibiotic effectiveness
• Chromosomes


  Coiled structures containing DNA, arranged in pairs in the nucleus
• Cell cycle


  Process of cell growth, DNA replication and division through mitosis
• Mitosis


  Cell division to form two genetically identical daughter cells