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
• 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
  • 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


  Provides structure and protection, not made of cellulose
• Differences between prokaryotic and eukaryotic cells: no mitochondria/chloroplasts in prokaryotes, no nucleus in prokaryotes
• Similarity between plant cells and prokaryotic cells: both have a cell wall
• Specialized cells


  Cells that change their size, shape and internal structures to carry out specific functions
• Plant specialized cells


  • Root hair cells
  • Xylem
  • Phloem
• Cell differentiation


  Process where different genes are turned on/off in cells to change their shape and structures, allowing them to become specialized
• Stem cells


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


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


  Has much 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, focus, then increase magnification
• Binary fission


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

  1. Use sterile technique

  2. Provide nutrients and oxygen

  3. Incubate at right temperature

  4. Prevent contamination
• Antibiotic resistance


  Measure clear zones around antibiotic discs on bacterial plates to determine resistance
• Chromosomes


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


  Process of cell division, including interphase to prepare and mitosis to divide
• Stem cell types


  Embryonic, adult, plant meristem
• Therapeutic cloning


  Using stem cells genetically identical to patient to grow replacement cells
• Ethical issues around embryonic stem cells: embryo cannot consent, seen as potential life
• 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
• Using embryonic stem cells

  Raises ethical issues as the embryo cannot consent
• Using adult stem cells


  Avoids ethical issues as the person can consent
• Unused embryos being destroyed is not accepted by some people as they view the embryo as potential life