topic 2- organisation

• Some organisms contain loads of cells, but how, you might wonder, do all these cells end up making
• Large Multicellular Organisms

  Made Up of Organ Systems
• Cells


  The basic building blocks that make up all living things
• The process by which cells become specialised for a particular job

  Differentiation
• As you know from page 14, specialised cells carry out apsellesse fusefoo
• Differentiation occurs during the development of a multicellular organism.
• These specialced cells form

  1. Tissues

  2. Organs

  3. Organ Systems
• Large multicelular organisms (e.g. squirrels) have different systems inside them for exchanging and transporting materials.
• Tissues

  Groups of similar cells that work together to carry out a particular function
• Tissues in mammals (like humans)

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Organs


  Groups of different tissues that work together to perform a certain function
• Organs in the digestive system

  • Stomach
  • Pancreas
  • Liver
  • Small intestine
  • Large intestine
• Organ Systems

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

  • Glands (e.g. pancreas, salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• Organ systems work together to make entire organisms
• Chemical reactions are what make you work. And enzymes are what make them work.
• Enzymes

  Catalysts produced by living things
• Living things have thousands of different chemical reactions going on inside them all the time. These reactions need to be carefully controlled to get the right amounts of substances.
• You can usually make a reaction happen more quickly by raising the temperature. This would speed up the useful reactions but also the unwanted ones too... not good. There's also a limit to how you can raise the temperature inside a living creature before its cells start getting damaged.
• Catalyst

  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Enzymes are all large proteins and all proteins are made up of chains of amino acids. These chains are folded into unique shapes, which enzymes need to do their jobs.
• Active site

  The unique shape that fits onto the substance involved in a reaction
• Enzymes are really picky-they usually only catalyse one specific reaction.
• Look and key model


  A simpler model of enzyme action where the active site has a fixed shape that fits the substrate
• Induced fit model

  A more accurate model of enzyme action where the active site changes shape a little as the substrate binds to it to get a tighter fit
• Changing the temperature

  Changes the rate of an enzyme-catalysed reaction
• If it gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme's active site, so the substrate won't fit any more. The enzyme is said to be denatured.
• Optimum temperature


  The temperature where an enzyme is most active
• If the pH is too high or too low

  It interferes with the bonds holding the enzyme together, changing the shape of the active site and denaturing the enzyme
• Optimum pH


  The pH where an enzyme works best
• Pepsin is an enzyme used to break down proteins in the stomach. It works best at pH 2, which means it's well-suited to the acidic conditions there.
• Digestive enzymes

  Enzymes produced by cells and released into the gut to break down food
• Starch, proteins and fats are BIG molecules. They're too big to pass through the walls of the digestive system, so digestive enzymes break these BIG molecules down into smaller ones like sugars (e.g. glucose and maltose), amino acids, glycerol and fatty acids. These smaller, soluble molecules can pass through the walls of the digestive system, allowing them to be absorbed into the bloodstream.
• Carbohydrases


  Enzymes that convert carbohydrates into simple sugars
• Carbohydrases


  • Amylase
• Amylase is made in three places: the salivary glands, the pancreas, and the small intestine.
• Proteases


  Enzymes that convert proteins into amino acids
• Proteases


  • Pepsin (in the stomach), proteases from the pancreas and small intestine
• Lipases


  Enzymes that convert lipids into glycerol and fatty acids
• Lipases


  • Lipases from the pancreas and small intestine