Movement of Molecules

Movement of Molecules

1. Dissolved Substances

   • Active transport
     • Goes against concentration gradient and requires energy from respiration.
       • Enables cells to absorb ions from dilute solutions.
   • Water moves by osmosis
     • Through a partially permeable membrane from a high concentration to a low concentration.
       • This is called a concentration gradient.
   • Sports Drinks
     • Contain waiter, sugar and ions.
       • The sugars replace sugars lost during energy release while exercising.
       • The water and ions replace the water and ions lost while sweating.
       • If not replaced, there is an inbalance and cells cannot work properly.
   • Effectiveness
     • Large Surface Area
       • In the lungs; alveoli.
       • In the small intestine; villi.
         • Extensive network of capillaries to absorb the products of digestion.
     • Thin walls
     • Efficient blood supply

2. Gaseous Exchange

   • Lungs are protected by the ribcage.
   • Breathing takes air in and out of the body so that oxygen can diffuse into the bloodstream and carbon dioxide out.
     • Air moves in when the diaphragm contracts and the ribcage expands.
     • Air moves out when the diaphragm relaxes and the ribcage moves back.