Download Cellular Respiration

Why is photosynthesis important?
Try to imagine a world without plants. The world would
certainly look different, and its atmosphere would also
be different. How would humans or other animals get the
oxygen they need?
Plants help maintain the atmosphere you breathe.
Photosynthesis produces as much as 90 percent of the
oxygen in the atmosphere. Without green plants, humans
would not have enough oxygen to breathe.
ACADEMIC VOCABULARY
energy
(noun) usable power
Reading Check
6. Name Which cellular
process converts food energy
into usable energy?
Cellular Respiration
All organisms require energy to survive. Energy is in the
chemical bonds in food molecules. A process called cellular
respiration releases energy. Cellular respiration is a series of
chemical reactions that convert the energy in food molecules into a
usable form of energy called ATP.
Releasing Energy from Sugars
Glucose is the sugar produced by photosynthesis. Glucose
molecules break down during cellular respiration. Much of
the energy released during this process is used to make ATP.
ATP is an energy storage molecule.
Cellular respiration occurs in the cytoplasm and
mitochondria of cells. This process requires oxygen and
produces water and carbon dioxide as waste products.
Key Concept Check
7. Explain What is cellular
respiration?
If your body did not break down the food you eat, you
would not have energy to do anything. All organisms must
break down their food to produce energy. Plants produce
their own food—glucose—during photosynthesis. Without
cellular respiration, plants could not grow, reproduce, or
repair tissues.
Comparing Photosynthesis
and Cellular Respiration
Photosynthesis requires light energy and the reactants
carbon dioxide and water. Reactants are substances that react
with one another during the process.
Oxygen and glucose are the products, or end substances,
of photosynthesis. Glucose is a molecule of stored energy.
Most plants, some protists, and some bacteria carry on
photosynthesis.
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Why is cellular respiration important?