bio 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
• Additional parts of a plant cell


  • Chloroplasts
  • Vacuole
  • Cell wall
• 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 in prokaryotes, no nucleus in prokaryotes
• Cells change size, shape and internal structures to carry out specific functions - these are called specialized cells
• Examples of specialized plant cells


  • Root hair cells
  • Xylem
  • Phloem
• Examples of specialized animal cells


  • Sperm cells
  • Nerve cells
  • Muscle cells
• Cell differentiation


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


  Undifferentiated cells that can differentiate into different cell types
• Plant cells can differentiate throughout life, animal cells mostly differentiate early and then just divide by mitosis
• Optical/light microscope


  Magnifies images using lenses and light, 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 lowest power lens and focus

  7. Increase magnification
• Chromosomes


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


  Process of cell growth, DNA replication, and cell division (mitosis)
• Types of stem cells


  • Embryonic
  • Adult
  • Plant (meristems)
• Therapeutic cloning can produce stem cells genetically identical to the patient
• There are ethical issues around using embryonic stem cells
• Diffusion


  Net movement of particles from high to low concentration
• 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
• Factors affecting rate of diffusion


  • Concentration gradient
  • Distance to travel
  • Temperature
  • Surface area of membrane
• Exchange surfaces have adaptations to maximise the rate of diffusion, such as thin walls, large surface area, and good blood/air supply
• Examples of exchange surfaces


  • Alveoli in lungs
  • Villi in small intestine
  • Leaves in plants