Topic 2 - Organisation

• Cells


  Make up all living things. Made up of organelles. For example muscle cells
• Tissue


  A group of specialised cells with a similar structure and function. For example muscle tissue.
• Organs


  Made from a group of different tissues working together to perform a particular function. For example the heart
• Organ systems


  Made from a group of organs with related functions working together to perform body functions. For example the digestive system
• Organelles (Sub cellular structures)


  parts in a cell For example nucleus or mitochondria
• Organism


  Multiple organ systems working together to form an organism. For example a human
• Levels of organisation

  Organelles ➔ cells ➔ tissues ➔ organs ➔ organ systems ➔ Organism
• Digestive system

  An organ system which is made up of different organs working together to break down food in order for it to be in a form which can be absorbed by cells.
• Digestion system is made up of:

  • Salivary glands
  • Pancreas
  • Stomach
  • Small intestines
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Digestion

  A process in which relatively large insoluble molecules are broken down into smaller soluble molecules that can be absorbed into the blood stream and delivered to cells in the body.
• Insoluble

  Can't be dissolved in a liquid
• Soluble

  Can be dissolved in a liquid
• Salivary glands/mouth

  • The teeth chew food which breaks it into smaller pieces
  • The amylase enzymes in saliva starts to digest starch into maltose
  • Lubricates the food in saliva so it's easier to swallow
• Oesophagus

  • The tube that connects the mouth to the stomach.
  • Uses contractions to push the food down - doesn't rely on gravity.
• Stomach

  • Food is digested by contractions from its muscular walls to churn and mix the food.
  • Protease enzymes start to digest proteins into amino acids.
  • Hydrochloric acid is present to kill bacteria in food and provides the optimum pH for enzymes to work.
• Small intestine

  • First section is where the food coming from the stomach finishes being digested by all the digestive enzymes produced in the small intestine.
  • Second section is lined with villi which absorb the digested food molecules takes place.
• Large intestine


  Water is absorbed from the remaining material
• Rectum


  Where faeces is stored after coming out of large intestine
• Anus


  Where faeces is removed from once its come from the rectum
• Pancreas

  • Produces all three digestive enzymes
  • Secretes enzymes in an alkaline fluid for digestion to raise the pH of fluid coming out of the stomach.
• Liver

  • Produces bile to emulsify fats
  • Breaks down amino acids that are not used to make proteins which produces urea.
• Gall bladder


  Stores bile which was produced in the liver.
• Bile


  Produced in the liver and stored in the gall bladder to then be released into the small intestines when needed.
• Bile

  • It is alkaline and used to neutralise the hydrochloric acid from the stomach since the enzymes in the small intestine have a higher optimum pH than the stomach.
  • It emulsifies fats (Breaks down large molecules into smaller molecules) - the larger the surface area (The smaller the molecule) the faster lipase can break down lipids into glycerol and fatty acids.
• Enzymes


  Biological catalysts (Substance which increases the rate of reaction without being used up)
• Enzymes

  • Made from protein
  • Digestive enzymes digest large insoluble food molecules into smaller soluble molecules which can be absorbed.
  • They speed up reactions
  • Each enzyme has a unique active site where a substrate is temporarily bound
  • Enzymes remain unchanged at the end of a reaction
• Digestive enzymes

  Amylase (Carbohydrases)

  Protease

  Lipase
• Amylase


  Breaks down starch into glucose. Produced in the salivary glands, pancreas and small intestine.
• Proteases


  Break down proteins into amino acids. Produced in the stomach, pancreas and small intestine.
• Lipase


  Break down lipids (fats) into glycerol and fatty acids. Produced in the pancreas and small intestine.
• Carbohydrase


  Breaks down carbohydrates into sugar. Produced in the salivary glands, pancreas and small intestine.
• Enzymes require an optimum:

  • Temperature
  • pH
• Enzymes denaturing


  When an enzyme active site changes shape because the temperature or pH has changed so much that the substrate won't be able to fit in the enzyme anymore.
• The lock and key theory

  This is a theory used to explain enzymes. The enzyme is like a lock with the substrate as they key - they can easily fit into the active site of the enzyme being a perfect fit.
• Metabolism


  The sum of all reactions happening in a cell or organism.
• Enzymes and metabolism

  Since enzymes speed up reactions they speed up the rate of metabolism in an organism.
• Enzymes and temperature

  • The optimum temperature of an enzyme in the body is around 37 °C.
  • The rate of the reaction increases as the temperature increases (because there are more successful collisions between enzyme and substrate because of the more energy from higher temperature.)
  • Up until its optimum
  • Then when above, it starts to rapidly decrease until the reaction stops because the enzyme has denatured. (the forces between the chains of amino acids break which changes the shape of the active site meaning the substrate can't fit.)
• Enzymes and pH

  • The optimum pH of an average enzyme is 7.
  • If the pH is too low or high the forces which hold the amino acid chains together will be affected and the enzyme will eventually denature if the pH is too low or high.
  • The closer to the optimum pH the higher the rate of reaction.
• Enzyme pH required practical

  To investigate the effect of pH on the rate of reaction of amylase.
• What is the name of special region of an enzyme that binds to the substrate? 

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