Bio Task 1

• Osmosis is the movement of water molecules through a semi-permeable membrane from an area of high water concentration to an area of low water concentration.
• Three domains of life

  • Eukaryota
  • Archaea
  • Bacteria
• Six kingdoms of life

  • Archaea
  • Bacteria
  • Protista
  • Fungi
  • Plantae
  • Animalia
• Archaea


  • Differ from bacteria in the composition of their cell membrane and wall, the structure of their ribosomes and their metabolism
  • Most Archaea are extremophiles - organisms that can live under extreme conditions
  • Thermophiles (high temperatures)
  • Acidophiles (love acidic environments)
  • Halophiles (love salty environments)
  • Environments that lack oxygen and light
• Prokaryotic cells


  Unicellular, no membrane-bound organelles or nucleus, only organelle is ribosomes, can have cell wall, single circular chromosome, may have plasmids, can have appendages like pili and flagella
• Eukaryotic cells


  Much more complex and larger (10-100μm) than prokaryotic cells, have membrane bound organelles, can be unicellular or multicellular, include Animalia, Plantae, Fungi, Protista
• Features of animal cells

  • Cell Membrane
  • Cytoplasm
  • Nucleus
  • Nucleolus
  • Endoplasmic reticulum
  • Ribosomes
  • Centrioles
  • Lysosomes
  • Golgi Bodies
  • Mitochondria
• Features of plant cells

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Vacuoles
  • Chloroplasts
  • Nucleus
  • Mitochondria
  • Ribosomes
  • Endoplasmic Reticulum
  • Golgi apparatus
• Types of microscopes


  • Light Microscope
  • Fluorescence Microscopy
  • Phase Contrast Microscope
  • Transmission electron microscope
  • Scanning electron microscope
• Light microscope


  Uses a series of lenses to magnify a specimen, total magnification is eyepiece magnification x objective lens magnification, provides resolution, magnification, and contrast
• Electron microscope


  Uses a beam of electrons instead of light, TEM produces 2D black and white images, SEM produces 3D black and white images
• Fluid mosaic model of cell membrane

  Two layers of phospholipids, hydrophobic tails inwards, hydrophilic heads outwards, allows fluidity and movement of proteins
• Components of cell membrane

  • Phospholipids
  • Proteins
  • Cholesterol
  • Carbohydrates
• Phospholipids


  Consist of a phosphorus head and two fatty acid tails, are amphiphilic
• Proteins in cell membrane

  Integral proteins are permanent, peripheral proteins are temporary, transmembrane proteins span both layers
• Cholesterol


  Gives stability to membrane without affecting fluidity, reduces permeability to small water-soluble molecules
• Carbohydrates


  Usually linked to protruding proteins or lipids, help in recognition and adhesion between cells, recognition of antibodies, hormones and viruses
• Freeze-fracture electron microscopy is used to demonstrate that proteins are embedded in cell membrane
• Substances needed by cells

  • Gases (O2 and CO2)
  • Nutrients (sugars, amino acids, glycerol and fatty acids)
  • Water (main solvent)
• Substances removed by cells

  • Waste (urea, uric acid and excess CO2)
  • Products secreted by cell to coat outside (mucus) or may pass to other cells (hormones)
• Permeability of different molecules

  • Small, uncharged (O2, CO2)
  • Lipid soluble, non-permeable (Alcohol, Steroids)
  • Small, polar (H2O, urea)
  • Small ion (K+, Na+, Cl-)
  • Large, polar, water soluble (C6H12O6)
• Factors affecting movement of substances across cell membranes

  • Chemical factors (Charge, Solubility, Hydrophobic/hydrophilic)
  • Physical factors (Diffusion, Osmosis, Active transport)
• Substances needed by cells

  • Gases (O2 and CO2)
  • Nutrients (sugars, amino acids, glycerol and fatty acids)
  • Water (main solvent)
• Substances removed by cells

  • Waste (urea, uric acid and excess CO2)
  • Products secreted by cell to coat outside (mucus) or may pass to other cells (hormones)
• Permeability of different molecules

  • Small, uncharged (O₂, CO₂) - Permeable
  • Lipid soluble, non-permeable (Alcohol, Steroids) - Permeable
  • Small, polar (H2O, urea) - Permeable or Semipermeable
  • Small ion (K+, Na+, Cl-) - Impermeable (Protein channels)
  • Large, polar, water soluble (C6H12O6) - Impermeable (Protein channels)
• Factors affecting movement of substances across cell membranes

  • Chemical factors (Charge, Solubility, Hydrophobic/hydrophilic)
  • Physical Factors (Shape and size)
• Concentration gradient


  Amount of substance on either side of the membrane
• Surface area to volume ratio

  Larger SA to volume ratio = faster rate of diffusion
• Diffusion


  The movement of any molecule from a region of high concentration to low concentration until equilibrium is reached
• Diffusion


  • Movement is down concentration gradient → passive
  • Difference in concentration, temperature and practical size affect the rate of diffusion until equilibrium is reached
  • When equilibrium is reached, the molecules still move randomly but there is net movement in any particular direction
• Simple diffusion


  Movement of molecule without help of transport proteins
• What molecules pass via simple diffusion?

  • Small uncharged molecules
  • Lipid soluble substances (e.g oxygen, carbon dioxide, alcohol, urea)
• Facilitated diffusion


  • Movement is facilitated by proteins in the membrane
  • More rapid than simple diffusion
  • Each protein that acts as a membrane transporter is specific to one or a few solutes
  • Allows larger charged molecules to pass through
• Types of facilitated diffusion

  • Through channel proteins
  • Through carrier proteins
• Channel Protein


  • Formed by protein that spans the whole cell membrane and allows for direct passage from one side to the other
  • Works like a gate that has open and closed states depending on electrical signals
  • Faster form of transport
  • Transports ions
• Carrier protein


  • Binds with a solute, then the protein changes shape to move the solute to the other side
  • Once released it returns to its original shape
  • Can become saturated and slower
  • Slower than channel proteins but quicker than simple diffusion
• Active transport


  • Movement of molecules from an area of low concentration to an area of high concentration
  • Requires ATP and carrier proteins
• Osmosis


  • The movement of water molecules for a region of high water concentration (high water potential) to a region of low water concentration (low water potential)
  • Does not require energy
  • Moves passively through aquaporins
  • Moves until equilibrium is reached
• Hypertonic, Isotonic, Hypotonic


  • Hypertonic: A solution that has a greater concentration of solutes compared to the inside of a cell
  • Isotonic: A solution that has an equal concentration of solutes compared to another solution or inside normal body cells
  • Hypotonic: A solution that has a lower concentration of solutes compared to another solution inside normal body cells
• Plasmolysis


  A cell that has lost its water because it's in a hypertonic solution/environment