Starter crossword burning food

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Across
  1. 1. The process of releasing energy from glucose in cells. (11)
  2. 3. The sugar broken down in respiration to release energy. (7)
  3. 5. The muscle that helps with breathing by contracting and relaxing. (9)
  4. 7. A structure in the heart that prevents backflow of blood. (5)
  5. 9. Tiny air sacs in the lungs where gas exchange occurs. (7)
  6. 10. A blood vessel that carries blood away from the heart. (6)
  7. 11. The lower chamber of the heart. (9)
  8. 12. The process of burning something to release energy. (10)
Down
  1. 2. Gas required for both burning food and respiration. (6)
  2. 4. a unit used to measure energy in food. (7)
  3. 6. The rhythmic throbbing of arteries caused by the beating of the heart. (5)
  4. 8. The element found in all food that is released as dioxide during respiration. (6)
  5. 10. The upper chamber of the heart. (6)
  6. 11. A blood vessel that carries blood toward the heart. (4)