B2: Cell organisation

• Organism


  A living thing made up of cells
• Large Multicellular Organisms


  • Made up of organ systems
• Cell specialisation


  The process by which cells become specialised for a particular job
• Differentiation


  The process by which cells become specialised during the development of a multicellular organism
• Organisation of cells in organisms

  1. Cells

  2. Tissues

  3. Organs

  4. Organ systems
• Tissues


  • Groups of similar cells that work together to carry out a particular function
  • Can include more than one type of cell
• Organ


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

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


  A group 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
• Enzyme


  A biological catalyst that increases the speed of a chemical reaction without being changed or used up in the reaction
• Enzymes


  • They are all proteins made up of chains of amino acids folded into unique shapes
  • Their unique shape allows them to catalyse specific reactions
• Active site


  The unique shape on an enzyme that the substrate fits into
• Substrate fits enzyme's active site

  Enzyme can catalyse the reaction
• Substrate doesn't fit enzyme's active site

  Enzyme cannot catalyse the reaction
• Enzymes


  • They have an optimum temperature and pH at which they work best
  • Temperatures or pH outside the optimum can denature the enzyme
• Investigating effect of pH on enzyme activity

  1. Add iodine solution to wells

  2. Heat water bath to 25°C

  3. Add amylase and buffer solution

  4. Add starch solution

  5. Sample every 30 seconds and test for starch with iodine

  6. Repeat with different pH buffers
• Rate of reaction


  A measure of how much something changes over time
• Calculating rate of reaction

  • Rate = 24 cm³ / 50 s = 0.48 cm³/s
• Carbohydrases


  Enzymes that break down carbohydrates into simple sugars
• Examples of Carbohydrases

  • Amylase
• Proteases


  Enzymes that break down proteins into amino acids
• Proteases


  • Pepsin, enzymes from pancreas and small intestine
• Lipases


  Enzymes that break down lipids into glycerol and fatty acids
• Lipases


  • Enzymes from pancreas and small intestine
• Bile


  • Produced in the liver, stored in the gall bladder, released into the small intestine
  • Neutralises stomach acid and emulsifies fats
• The body makes use of the products of digestion to make new carbohydrates, proteins and lipids
• Enzymes used in the digestive system are produced by specialised cells in glands and in the gut
• Different enzymes catalyse the breakdown of different food molecules
• The stomach produces hydrochloric acid to kill bacteria and provide the right pH for protease enzymes
• The pancreas produces protease, amylase and lipase enzymes which are released into the small intestine
• The small intestine is where the digested food is absorbed into the blood
• The large intestine absorbs excess water from the food leaving faeces
• Digestion


  1. Digested food is absorbed out of the digestive system into the blood

  2. Faeces (made up mainly of indigestible food) are stored before they are expelled through the anus
• Lungs


  • Located in the thorax
  • Separated from lower body by diaphragm
  • Air goes through trachea, bronchi, bronchioles to alveoli
• Alveoli


  Small air sacs in the lungs where gas exchange takes place
• Gas Exchange


  1. Oxygen diffuses from alveoli into blood

  2. Carbon dioxide diffuses from blood into alveoli

  3. Oxygen and carbon dioxide transported to and from body cells
• Calculating Breathing Rate


  1. Count breaths in a set time period

  2. Divide total breaths by time to get breaths per minute
• Circulatory System


  • Double circulatory system - one circuit for deoxygenated blood, one for oxygenated blood
  • Heart contracts to pump blood around the body