Learn more about how carbon cycles through the Earth in Earth and Space 22.2
Only some organisms photosynthesise, but all organisms respire. Photosynthesis and respiration help control the balance between carbon dioxide and oxygen in the atmosphere.
The equations that describe both processes are almost the reverse of one another: z The reactants of respiration (glucose and oxygen) are the products of photosynthesis.
z The products of respiration (water and carbon dioxide) are the reactants of photosynthesis.
ENERGY STORED C6H12O6 + 6O2 ENERGY STORED respiration photosynthesis ENERGY RELEASED 6CO2 + 6H2O SUNLIGHT
z Photosynthesis is a building reaction. This means that it temporarily stores energy.
z Respiration is a breaking reaction. This means that it releases stored energy.
Confirming that living organisms respire and dead organisms do not respire
1. Plan, design, carry out and write up an investigation to show that respiring organisms release energy as heat. This set-up should also allow you to confirm if carbon dioxide is produced as a waste product by respiring organisms.
Before you start this investigation, consider the following:
a. What should you use as a control? b. What chemical is used to test for the presence of carbon dioxide? What is the positive result for this test? Ask your teacher if there are carbon dioxide sensors in the school laboratory that could be used.
