School resources - organisation

• Principles of organisation


  • organism
  • organ system
  • organ
  • tissue
  • cell
• Organisms


  • human
  • frog
  • oak tree
  • orchid
• Organism


  A group of organ systems working together
• Organ system


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


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


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


  The smallest structural and functional unit of an organism
• Animal tissues


  • muscle
  • blood
  • nerve
  • epithelial
• Plant tissues


  • xylem
  • phloem
• The human 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


  • Amylase
  • Protease
  • Lipase
• 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" model

  Explains enzyme action - the shape of the active site of the enzyme is specific for each substrate
• The products of digestion are used to build new carbohydrates, lipids and proteins in the body. Some glucose is used in respiration
• Enzyme activity


  Affected by temperature and pH. Specific conditions are needed to keep enzymes working at their best (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
• Acidic conditions


  Enzymes in the stomach work best
• Alkaline conditions


  Enzymes in the pancreas and small intestine work best
• 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
• The heart


  An organ that pumps blood around the body in a double circulatory system
• Double circulatory system


  1. Right ventricle pumps blood to the lungs for gas exchange

  2. Left ventricle pumps blood around the rest of the body
• Coronary arteries supply oxygen rich blood to the heart muscle
• Pacemaker


  Group of cells in the right atrium that control the natural resting heart rate
• Artificial electrical pacemakers are used to correct irregularities in the heart rate
• Lungs


  Where gas exchange takes place - oxygen and carbon dioxide are exchanged in the tiny air sacs (alveoli)
• Arteries


  • Carry blood away from the heart, have thick muscular walls, small lumen, carry blood under high pressure
• Veins


  • Carry blood to the heart, have thin walls, large lumen, carry blood under low pressure, have valves
• Capillaries


  • Connect arteries and veins, one cell thick, carry blood under very low pressure
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Plasma


  Pale yellow fluid part of blood, transports cells, CO2, hormones and waste
• Red blood cells


  Have no nucleus (more room to carry O2), contain the red pigment haemoglobin which carries O2, have a large surface area to volume ratio for faster diffusion of oxygen
• White blood cells


  An important part of the immune system, some produce antibodies and others surround and engulf foreign cells, all have a nucleus
• Platelets


  Tiny fragments of cells (no nuclei), clump together to help form clots, protect the body by stopping/reducing bleeding
• Atherosclerosis


  A cause of coronary heart disease where layers of fatty material build up inside the coronary arteries, narrowing them and reducing blood flow