Organisation and the digestive system

• Levels of organisation in living organisms

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organisms
• Cells


  The basic unit of life, made up of different organelles
• Tissues


  Groups of similar cells working together to perform a specific function
• Organs


  Structures made up of different tissues, which carry out a specific function
• Organ systems


  Groups of organs working together to perform a specific overall function
• Organisms


  A living thing that can function independently
• Organs of the digestive system

  • Mouth
  • Stomach
  • Small intestine
  • Large intestine
  • Liver
  • Gall bladder
  • Pancreas
• Mouth


  Where food is chewed
• Stomach


  Churns food and releases hydrochloric acid to kill pathogens
• Small intestine


  Where digested food is absorbed into the blood
• Large intestine


  Where water and minerals are absorbed into the blood
• Liver


  Produces bile to emulsify fats
• Gall bladder


  Stores and concentrates bile
• Pancreas


  Produces digestive enzymes
• Digestive enzymes


  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrases


  Break down carbohydrates into simple sugars
• Proteases


  Break down proteins into amino acids
• Lipases


  Break down fats into glycerol and fatty acids
• Enzyme


  Large protein that speeds up reactions without being consumed
• Substrate


  The molecule that an enzyme acts on
• Enzymes


  • They are not changed in the reactions they catalyse
  • They have an active site with a specific shape that only fits certain substrates
• How enzymes work (lock and key theory)


  1. Enzyme's active site has a specific shape

  2. Substrate collides with the active site of enzme and becomes attached

  3. Reaction occurs at active site, enzymes can break down molecules or bind them together

  4. Products are released
• As temperature increases


  The rate of enzyme-catalysed reactions increases
• At very high temperatures


  Enzymes become denatured and stop working
• At extremes of pH


  Enzymes become denatured and stop working
• Denatured enzyme


  An enzyme that has lost its 3D shape and can no longer catalyse reactions
• Optimum temperature


  The temperature at which an enzyme works fastest
• Diffusion


  Spreading out of particles in a solution or gas from an area of high to lower concentration
• Factors affecting the rate of diffusion

  • Large surface area=the more particles can get through and diffuse
  • Very steep concentration gradient=rapid diffusion
  • Increase in temperature=more kinetic energy/faster rate of diffusion
  • Thin Surface (one cell thick)=More particles can get through and diffuse because there’s a SHORT DIFFUSION PATHWAY
• Osmosis


  Diffusion of water from a dilute solution to a more concentration solutio, through a partially permeable membrane (allowing certain substances through via cell membrane)
• Osmosis is a passive process


  It relies on kinetic energy of the water molecules
• Osmosis in a plant cell: Hypotonic Solution

  • Cell is turgid: More net movement of water into the cell and less out of cell
  • Cell walls prevent cell from bursting
• Osmosis in Plants: Isotonic solution

  • No Net movement into and out of cell by osmosis
  • Same concentration as cyptoplasm
• Osmosis in Plants: Hypertonic solution

  • Cell is flacid
  • Greater net movement of water out of the cell by osmosis
  • Cell is being plasmolysed
• Osmosis in animal cells: hypotonic solution

  • Greater net movement of water into the cell
  • No cell wall and therefore cell bursts
• Osmosis in animal cells: Hypertonic solution

  • Cytoplasm shrinks
  • Greater net movement of water out of the cell
• Microscopes: Light

  • Inexpensive to buy and operate
  • Has lower resolution
• Microscopes: TEM

  • Provides highest resolution in microscope field
  • Instrument is extremely large and expensive
• Microscopes:SEM

  • Has a large depth field
  • Must be housed in an area free of electrical interference
• RPA: Osmosis in potato tissue

  • As sucrose concentration increased, the mass of the chip decreased