Oranginastion

• Cells


  The basic building blocks of all living organisms
• Differentiation


  The process by which cells become specialised for a particular job
• Differentiation occurs during the development of a multicellular organism
• Tissue


  A group of cells with a similar structure, and they work together to carry out a particular function
• Organ


  A group of tissues that work together to perform a specific function
• Organs in the digestive system

  • Stomach
  • Liver
  • Small intestine
  • Large intestine
• Organ system


  A group of organs working together to perform a particular function
• Organs in the digestive system

  • Glands producing digestive juices
  • Stomach and small intestine digesting food
  • Liver producing bile
  • Small intestine absorbing food
  • Large intestine absorbing water
• Enzymes

  Biological catalysts produced by living things that speed up chemical reactions
• Enzymes


  • They are like proteins and are made up of chains of amino acids folded into unique shapes
  • They have an active site with a unique shape that fits the substrate
• Substrate


  The other substance involved in the enzyme-catalysed reaction
• Enzymes usually only catalyse one specific reaction because the substrate has to fit the active site
• Lock and key model

  A simpler model of how enzymes work, where the active site has a fixed shape that the substrate fits into
• Induced fit model


  A more accurate model where the active site changes shape a little as the substrate binds to get a tighter fit
• pH


  The acidity or alkalinity of a solution, which affects enzyme shape and activity
• Enzymes have an optimum pH that they work best at, often around neutral pH 7
• Catalyst


  A substance that increases the speed of a reaction without being changed or used up in the reaction
• As temperature increases


  The rate of an enzyme-catalysed reaction increases
• If temperature gets too high, the bonds holding the enzyme together will break, changing the shape of the active site and denaturing the enzyme
• Enzymes have an optimum temperature that they work best at
• Investigating enzymatic reaction


  1. Put iodine solution in wells

  2. Heat water to 35°C

  3. Add amylase and buffer solution

  4. Add starch solution

  5. Take samples every 30 seconds and test with iodine

  6. Repeat with different pH buffers
• Control variables


  Concentration and volume of amylase, temperature
• Independent variable


  pH level
• Dependent variable


  Time taken for starch to be broken down
• Digestive enzymes


  Convert large food molecules into smaller, soluble molecules that can be absorbed
• Digestive enzymes


  • Carbohydrases (e.g. amylase)
  • Proteases
  • Lipases
• The products of digestion are used to build new carbohydrates, lipids and proteins, and some is used as glucose for respiration
• Bile


  Made in the liver, stored in the gallbladder, and released into the small intestine
• Hydrochloric acid in the stomach

  Makes the pH too acidic for enzymes to work properly
• Bile


  Neutralises the acid and makes the conditions alkaline, which increases the rate of fat breakdown by lipases
• Enzymes used in the digestive system are produced by specialised cells in glands and gut lining
• Preparing a food sample

  1. Grind up food

  2. Add distilled water

  3. Filter to get a solution
• Benedict's test for reducing sugars


  1. Add Benedict's solution to food sample

  2. Heat in water bath for 5 minutes

  3. Colour change indicates presence of reducing sugars
• Biuret test for proteins

  1. Add biuret solution to food sample

  2. Purple colour change indicates presence of proteins
• Iodine test for starch

  1. Add iodine solution to food sample

  2. Blue-black colour change indicates presence of starch
• Sudan III test for lipids


  1. Add Sudan III stain to food sample

  2. Red layer at top indicates presence of lipids
• Lungs


  Large pink spongy organs in the thorax, protected by the rib cage and surrounded by the pleural membrane
• Air flow through the lungs

  1. Trachea

  2. Bronchi

  3. Bronchioles

  4. Alveoli
• The alveoli are surrounded by a network of blood capillaries where gas exchange takes place
• Oxygen and carbon dioxide diffusion in the lungs

  Oxygen diffuses from alveoli into blood, carbon dioxide diffuses from blood into alveoli