Module 1

• Cells are the basis of life
• Cell theory


  • All organisms are made up of one or more cells
  • Cells are the fundamental unit of life
  • All cells come from pre-existing cells
• Prokaryotic cells


  Less complex with no true nucleus or other membrane-bound organelles
• Eukaryotic cells


  Contain a nucleus and membrane-bound organelles
• Differences between prokaryotic and eukaryotic cells

  • DNA storage
  • Membrane-bound organelles
  • Cell wall
  • Size
• Microscopes


  Used to visualise cells and their contents
• Light microscope


  • Uses light to visualise cells
  • Provides magnification and resolution
• Magnification


  Ratio of enlargement (or reduction) of an image
• Resolution


  Ability of the lens to show fine details of the specimen
• Field of view (FOV)


  Area visible when looking through the microscope
• Electron microscope


  • Uses electron beams instead of light
  • Provides increased resolution and magnification
• Scanning electron microscope (SEM)

  Scans the surface of the specimen
• Transmission electron microscope (TEM)

  Produces images of internal organelles
• Staining techniques


  Use dyes to stain different cellular structures
• Lighting techniques


  Such as phase-contrast microscopy, enhance image quality
• Diffusion


  Movement of liquids and gases from high to low concentration
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Cell membrane


  Aids in exchanging materials within the internal and external environment
• Phospholipid bilayer


  Composition of the cell membrane
• Passive transport


  Movement of small, non-polar, and neutral substances through the membrane without requiring energy
• Active transport


  Movement of large, polar, and charged molecules through the membrane, requiring energy in the form of ATP
• Passive transport


  Small, non-polar, and neutral substances including water, oxygen and carbon dioxide can easily move through the membrane via passive transport. Passive transport does NOT require energy in the form of ATP.
• Passive transport


  1. Moves water molecules through osmosis

  2. Moves ions through facilitated diffusion using protein channels embedded within the cell membrane

  3. Substances move down their concentration gradient from high concentration to low concentration areas
• Active transport


  Large, polar, and charged molecules such as lipids and carbohydrates cannot easily cross the cell membrane and therefore move via active transport which requires both the protein channels and ATP. Active transport moves substances up their concentration gradient from areas of low to high concentration.
• Endocytosis


  1. Cells require movement of large amounts of materials into the cells

  2. The plasma protein folds around the extracellular material to form a vesicle that engulfs the material into the inside of the cell

  3. Types: Phagocytosis, Pinocytosis, Receptor-mediated endocytosis
• Exocytosis


  1. Exports materials such as hormones and waste products outside of the cell

  2. The materials are expelled in vesicles that fuse with the membrane to be transported out of the cell
• Because they rely on diffusion and osmosis, the exchange of materials into and out of the cell is limited by the size of the cell. Cells are generally smaller than 1mm in size and if they were to grow beyond that, metabolic wastes would accumulate and nutrients would be inefficiently transported.
• Surface Area to Volume ratio (SA:V)

  Cells must maintain a high Surface Area to Volume ratio to allow efficient exchange of materials
• Metabolic wastes such as nitrogenous wastes must be removed from the organism's body for normal cellular functioning.
• Ammonia


  Highly toxic nitrogenous waste produced from the breakdown of proteins in the cell
• Urea


  Less toxic form of nitrogenous waste that requires less water for excretion, produced in mammals
• Autotrophs


  • Obtain nutrients by performing photosynthesis within their chloroplasts
  • The numerous flattened discs in the chloroplast increases the surface area thus allowing higher rate of photosynthesis to occur
• Heterotrophs


  • Consume other organisms to obtain nutrients
  • Produce chemical energy (ATP) through cellular respiration that occurs in the mitochondria
  • The inner mitochondrial membrane is folded to increase its surface area and thus maximise cellular respiration rate
• Photosynthesis


  1. Light-dependent stage

  2. Light-independent stage
• Cellular respiration


  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain
• Metabolism


  The collection of life-sustaining chemical reactions which involves anabolism and catabolism
• Catabolism


  Breaks down complex nutrients such as glucose in order to release energy for cellular use
• Anabolism


  Synthesis of simple nutrients into more complex ones for energy storage
• Enzymes


  Proteins that catalyse reactions by lowering the energy level required to start the reaction
• Enzyme reaction models


  • Lock and key model
  • Induced fit model