Food – Our Body’s Source of Energy

At this point in our study of enzymes and digestion, students have learned how plants capture the energy in sunlight and store it as chemical potential energy in glucose molecules.  Animals (and plants!) metabolize glucose using cellular respiration, transferring the chemical potential energy from glucose to ATP (adenosine triphosphate), the energy currency of cells.  Photosynthesis takes place in chloroplasts, while cellular respiration occurs in mitochondria.

In The Breath of Life reading, students learned how the respiratory system of humans enables gas exchange, with the lungs inhaling oxygen and exhaling carbon dioxide.  The gas exchange occurs within the alveoli, thin-walled sacs inside the lungs.  The reading introduced the concept of feedback systems, focusing on the special nerve cells in the cardiovascular and nervous systems that can sense changes in pH.  As carbon dioxide builds up, the blood becomes more acidic, and the lungs are forced to exhale to rid the body of carbon dioxide which then brings the pH back to normal levels.

For today’s lesson, we once again turned to our textbook and students were instructed to read pages 328-332 and complete the associated worksheet.  The assigned reading was titled Food: Our Body’s Source of Energy and Structural Materials.  Now that students understand the link between photosynthesis (chemical potential energy stored in glucose), cellular respiration (glucose metabolized to transfer the energy in glucose to ATP), and the larger connection with the respiratory and cardiovascular systems, it is time to learn more about how the digestive system makes use of the variety of foods available to us.  It is time to think beyond glucose.


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