B3: organisation and the digestive system

• Levels of organization in the body

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organisms
• Cells

  Smallest unit of life, made up of organelles like nucleus, cell membrane, cytoplasm, mitochondria, ribosomes
• Tissues

  Similar cells working together to perform a specific function
• Organs


  Collection of tissues working together to perform a specific function, e.g. heart
• Organ systems

  Collection of organs working together to perform a specific overall function, e.g. digestive system
• Organisms

  Any living thing, comprised of multiple organ systems
• Digestive system

  1. Mouth

  2. Esophagus

  3. Stomach

  4. Liver

  5. Small intestine

  6. Large intestine
• Saliva


  Contains digestive enzyme amylase that breaks down carbohydrates
• Stomach

  Contains hydrochloric acid and enzymes to break down food
• Liver

  Produces bile to help break down fats
• Small intestine


  Where most absorption of nutrients takes place
• Large intestine

  Processes and removes waste
• Gallbladder


  Stores bile produced by the liver
• Proteins

  Broken down by protease enzymes into amino acids
• Carbohydrates


  Broken down by amylase enzyme into glucose
• Lipids (fats)

  Broken down by lipase enzyme into fatty acids and glycerol, also emulsified by bile
• Food tests

  1. Biuret test for proteins

  2. Iodine test for carbohydrates/starch

  3. Benedict's test for simple sugars

  4. Ethanol and water test for lipids
• Enzyme mechanism

  Lock and key - enzyme active site binds to specific substrate, changes shape to break it down
• Enzymes

  Biological catalysts that speed up reactions without being consumed
• Enzyme activity

  Affected by temperature and pH, has an optimum range for maximum activity
• Enzymes can become denatured at extreme temperatures or pH levels, losing their activity