Biology topic 2

• Multicellular Organisms are Made Up of Organ Systems
• Cell


  Basic building blocks that make up all living organisms
• Differentiation

  The process by which cells become specialised for a particular job
• Specialised cells carry out a particular function
• Differentiation occurs during the development of a multicellular organism
• Specialised cells form tissues, which form organs, which form organ systems
• Multicellular organisms (e.g. humans) have different systems inside them for changing and transporting materials
• Tissue

  A group of similar cells that work together to carry out a particular function
• Examples of tissues in mammals (like humans)

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Muscular tissue

  Contracts (shortens) to move whatever it's attached to
• Glandular tissue


  Makes and secretes chemicals like enzymes and hormones
• Epithelial tissue

  Covers outside and inside of stomach
• Enzymes

  Catalysts produced by living things
• Enzymes

  • They are catalysts
  • They are produced by living things
• Enzyme-catalysed reactions

  Need to be carefully controlled to get the right amounts of substances
• Living things have thousands of different chemical reactions going on inside them all the time
• Increasing temperature


  Can usually make a reaction happen more quickly
• Increasing temperature would speed up the useful reactions but also the unwanted ones too... not good
• There's also a limit to how high temperatures can be before cells start getting damaged
• Catalyst

  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Enzymes reduce the need for high temperatures and we only have enzymes to speed up the used chemical reactions in the body
• Enzymes

  • They have special shapes so they can catalyse reactions
  • They are large proteins made up of chains of amino acids
  • They have an active site with a unique shape that fits onto the substance involved in a reaction
• Enzymes are really picky - they usually only catalyse one specific reaction
• Substrate

  The substance that an enzyme acts on
• Enzyme action

  1. Substrate binding

  2. Induced fit

  3. Catalysis

  4. Product release
• The active site changes shape a little as the substrate binds to it to get a tighter fit. This is called the 'induced fit' model of enzyme action
• Enzymes speed up reactions
• Tissues

  • They are organised into organs
• Organ


  A group of different tissues that work together to perform a certain function
• Tissues in the stomach

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Organs are organised into organ systems
• Organs in the digestive system

  • Glands (eg, the pancreas and salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• Organ systems work together to make entire organisms
• Enzymes

  • They need just the right conditions to work properly
  • They have an optimum temperature and pH that they work best at
• Effect of temperature on enzymes

  1. Increasing temperature increases rate at first

  2. If temperature gets too high, enzyme structure is disrupted (denatured)

  3. Enzyme has an optimum temperature where it is most active
• Effect of pH on enzymes

  1. pH that is too high or too low disrupts enzyme structure (denatures)

  2. Enzyme has an optimum pH where it is most active
• Most enzymes catalyse just one reaction
• Rate of reaction

  Measure of how much something changes over time
• Calculating rate of reaction

  1. Rate = 1000 / time

  2. Units are per unit time (e.g. cm³/s)
• Catalase enzyme catalyses breakdown of hydrogen peroxide into water and oxygen