B3-Organisation and the digestive system

• Levels of biological organisation

  • Cell
  • Tissue
  • Organ
  • Organ system
  • Organism
• Cell


  The smallest structural and functional unit of an organism
• Tissue


  A group of similar cells with a similar structure and function
• Organ


  A group of tissues working together to perform a specific function
• Organ system


  A group of organs working together to perform a specific function
• Organism


  A group of organ systems working together
• Tissues


  • Muscle tissue
  • Blood
  • Xylem
  • Phloem
• Organs


  • Heart
  • Stomach
  • Leaf
• The digestive system is an example of an organ system where different organs work together to digest and absorb food
• Digestion


  Where large insoluble molecules are broken down into smaller soluble ones that can be absorbed into the bloodstream
• Digestion occurs in the GUT (tube from the mouth to the anus) and it relies on ENZYMES (biological catalysts)
• Digestive enzymes


  • Salivary amylase
  • Protease
  • Lipase
• Salivary amylase

  Breaks down carbohydrates into simple sugars
• Protease


  Breaks down proteins into amino acids
• Lipase

  Breaks down fats and oils (lipids) into fatty acids and glycerol
• Lock and key theory

  A model to explain enzyme action where the shape of the active site of the enzyme is specific for each substrate
• Enzymes are made of proteins and are biological catalysts - substances that increase the rate of chemical reactions without being used up
• Enzyme activity is affected by

  Temperature and pH
• Specific conditions are needed to keep enzymes working at their optimum conditions
• Enzymes control the chemical reactions in the body, this is known as metabolism
• Increasing temperature


  Initially increases the rate of enzyme reactions due to increased collisions, but if too high the enzyme will denature
• Stomach releases acid


  Enzymes in the stomach work best in acidic conditions
• Enzymes in the pancreas and small intestine

  Work best in alkaline conditions
• Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area
• Alkaline conditions and large surface area


  Increase the rate of fat breakdown by lipase