biology topic 1

• Eukaryotes


  Animals and plants
• Animal cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
• Plant cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Sap vacuole
  • Chloroplast
• Prokaryotes


  Bacterial cells with no nucleus or subcellular structures with membranes
• Approximate sizes: Animal cell 10 micrometers, Plant cell 50 micrometers, Prokaryote 5 micrometers
• Nerve cell


  • Cell body
  • Dendrites
  • Axon
  • Insulating sheath
  • Axon terminals
• Sperm cell


  • Mid piece with mitochondria
  • Tail
  • Acrosome
  • Nucleus
• Muscle cell


  • Fibers for contraction
  • Mitochondria
  • Glycogen store
• Xylem cell


  • No end plates
  • No cytoplasm
  • Lignin rings for support
• Phloem cell


  • Little cytoplasm
  • End plates with pores
  • Companion cells
• Root hair cell


  • Large surface area
  • Many mitochondria
• Microscopes


  Simple microscopes have low magnification and resolving power

  Electron microscopes have high magnification and resolving power
• Calculating magnification

  Magnification = Size of image / Size of real object
• Bacteria divide by binary fission
• Growing uncontaminated bacterial cultures

  Sterilise equipment

  Inoculate agar plate

  Incubate at 25°C

  Seal plate to prevent contamination
• Testing antibiotics/antiseptics

  Place antibiotic discs on agar with bacteria

  Measure area of bacterial death around discs
• Cell cycle

  Growth and DNA replication

  Mitosis - chromosomes line up and separate

  Cytoplasm and cell membrane divide
• Stem cells


  Undifferentiated cells that can develop into specialised cells
• Cell growth and division

  1. Cell grows and increases number of subcellular structures

  2. DNA replicates to form two copies of each chromosome

  3. Chromosomes line up along center and are pulled to each end of cell

  4. Cytoplasm and cell membranes divide to form two genetically identical cells
• Mitosis

  The process of cell division described above
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells (meristem tissue)
• Embryonic stem cells

  • Undifferentiated
  • Can be cloned
  • Can differentiate into most other cell types
• Adult stem cells

  • Found in bone marrow
  • Can differentiate into many cell types, mainly blood cells
• Plant stem cells

  • Found in meristem tissue in root and shoot tips
  • Can differentiate into any plant cell
• Therapeutic cloning

  1. Patient body cell nucleus removed and inserted into empty human egg cell

  2. Cloned to produce stem cells

  3. Stem cells differentiated to make specialized cells/tissues for treatment
• Diffusion


  Spreading out of particles in a solution or gas, with net movement from higher to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Active transport

  Movement of particles from lower to higher concentration, requires energy
• Examples of diffusion in living things

  • Oxygen diffusing into cells from blood
  • Carbon dioxide diffusing out of cells into blood
  • Urea diffusing out of cells
• Examples of active transport in living things

  • Sugar absorption in small intestine
  • Mineral ion absorption in root hair cells
• Surface area to volume ratio

  • Measure of how much surface area an organism has relative to its volume
  • Smaller organisms have higher ratio, allowing sufficient transport of molecules
• Adaptations for exchange systems in larger organisms

  • Villi and microvilli in small intestine to increase surface area
  • Thin walls for short diffusion distance
  • Many mitochondria for active transport energy
  • Good blood supply to maintain concentration gradient
• Adaptations of alveoli in lungs

  • Large surface area
  • Thin walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Ventilation to maintain oxygen concentration
• Adaptations of leaves

  • Flat and thin to provide large surface area
  • Air spaces between cells to increase diffusion rate
  • Stomata that can open/close to regulate gas exchange
• Adaptations of gills in fish

  • Many gill filaments to provide large surface area
  • Thin capillary walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Fresh water flowing over to maintain oxygen concentration
• Osmosis

  Diffusion of water from a dilute to a concentrated solution through a partially permeable membrane
• Osmosis in plant cells


  Water moves into the cell, making it turgid
• Osmosis in root hair cells


  Water moves into the cell from the dilute soil solution
• Investigating effect of solutions on plant tissue mass

  1. Prepare solutions of different concentrations

  2. Cut equal-sized plant tissue samples

  3. Immerse samples in solutions for set time

  4. Measure mass change of samples
• Potato tissue in concentrated solution


  Water moves out of potato, causing it to lose mass