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Photosynthesis and Cellular Respiration Test
Study Sheet
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All living things need a source of energy to carry on their life activities.
Food provides the energy living things need to survive.
Photosynthesis:
 During the process of photosynthesis, plants and other organisms use energy from
sunlight to make their own food.
 The food-making process of plants, some protists, and some bacteria is called
photosynthesis.
 Photosynthesis is the process by which plants and some other organisms convert
carbon dioxide and water into oxygen and organic compounds known as sugars.
 Glucose is a simple sugar produced during photosynthesis.
 Autotrophs are organisms that can make their own food.
 Heterotrophs cannot make their own food. Heterotrophs depend on plants and other
photosynthetic organisms for a food source, or they eat other organisms that eat
autotrophs.
 The process of photosynthesis is powered by sunlight.
 The sunlight is absorbed by a green pigment in leaves called chlorophyll. (A
pigment is a chemical that absorbs some wave lengths of light and reflects others.)
 Structures called chloroplasts contain chlorophyll. It is in the chloroplasts that carbon
dioxide and water are converted into glucose and oxygen. (Water vapor is also
produced during photosynthesis.)
 The raw materials of photosynthesis are water and carbon dioxide.
 Water enters the plant through its roots. It moves upward in the stem to the leaves where photosynthesis occurs.
 Carbon dioxide enters the plant through tiny openings in the leaves called stomata
(singular = stoma). Guard cells surrounding the stomata regulate the amount of
carbon dioxide coming into the leaves. (The guard cells also regulate the amount of
water vapor and oxygen that leave the cell as by-products of photosynthesis.)
 Deciduous trees lose their leaves in winter and their leaves change color in the Fall.
Evergreen trees or conifers do not lose their leaves in winter and keep their green
color in Fall.
 Environmental conditions that cause leaves to stop making food are: the temperatures
become lower (colder), and the day becomes shorter (less daylight).
 Paper Chromatography is used to separate the pigments found in the leaves of
plants. It uses alcohol to separate the pigments found in leaves. Besides chlorophyll,
the other pigments found in the leaves are carotene (orange), xanthophyll (yellow),
anthocyanin (red) and tannin (brown).
Cellular Respiration:
 The process by which organisms get energy from food is called cellular respiration.
 During cellular respiration, cells break down simple organic food molecules such as
glucose and release the energy they contain.
 This process is called cellular respiration because it happens in cells.
 The raw materials of cellular respiration are glucose and oxygen.
 The products of cellular respiration are carbon dioxide, water, and energy (ATP).
 The “waste product” produced by animals during cellular respiration that is used by
plants in photosynthesis is carbon dioxide.
 Energy is food is locked into the chemical bonds which are like links that hold the
atoms of the molecules together.
 The energy created by cellular respiration is stored in a molecule called ATP.
 Fermentation is a kind of cellular respiration that does not require oxygen. This is
called anaerobic respiration.
 Fermentation is an anaerobic process. That means it takes place without oxygen.
(Aerobic means “with oxygen.)
 Fermentation of yeast results in alcohol as a by-product.
 When the human body is involved in strenuous exercise and the lungs cannot provide
the muscles with oxygen fast enough to meet its needs, lactic acid builds up. This is a
type of fermentation called lactic-acid fermentation. Anaerobic respiration is not as
efficient as aerobic respiration. It produces far less energy.
Comparing Photosynthesis and Cellular Respiration:
 The raw materials of photosynthesis are the products of cellular respiration.
 The raw materials of cellular respiration are the products of photosynthesis.
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These two processes are thought of as opposite processes. Together, photosynthesis
and cellular respiration form a cycle that keeps the levels of carbon dioxide and
oxygen fairly constant in the atmosphere.