BIOLOGY
UNIT 3: Cellular Energetics
NAME _____________________________
Date _______________ Period _______
Cellular Respiration Worksheet
Directions: Read each paragraph and then answer the follow-up questions. All answers can be
found in the readings.
PART ONE: Mitochondria
Mitochondria are known as the powerhouses of the cell. They are
organelles that act like a digestive system that takes in nutrients, breaks
them down, and creates energy for the cell. The process of creating
cellular energy is known as cellular respiration. Most of the chemical
reactions involved in cellular respiration happen in the mitochondria. A
mitochondrion is shaped perfectly to maximize its efforts.
1. What is a nickname for the mitochondria? _________________________
2. What is the function (job) of the mitochondria? _____________________
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3. What is a good analogy (similar comparison) for the mitochondria? ___________________________
4. What is cellular respiration? __________________________________________________________
5. Where does the process of cellular respiration occur? ___________________________
PART TWO: Cellular Respiration
Organisms, such as plants and algae, can trap the energy in sunlight through
photosynthesis and store it in the chemical bonds of carbohydrate molecules. The principal
carbohydrate formed through photosynthesis is glucose. Other types of organisms, such as
animals, fungi, protozoa, and a large portion of the bacteria, are unable to perform this
process. Therefore, these organisms must rely on the carbohydrates formed in plants to
obtain the energy necessary for their metabolic processes. This means they must eat plants
and other animals in order to gain energy. Organisms that must consume food for energy
are called heterotrophs. In other words, heterotrophs cannot perform photosynthesis.
6. Where do organisms that perform photosynthesis store energy? ______________________________
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7. What carbohydrate is formed during photosynthesis? ________________________
8. What do we call organisms that cannot perform photosynthesis? _____________________________
9. How do organisms that cannot perform photosynthesis obtain energy? ________________________
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10. What are some examples of organisms that cannot perform photosynthesis? ___________________
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Cells take the carbohydrates into their cytoplasm, and through a complex series of
metabolic processes, they break down the carbohydrates and release the energy. The
energy is generally not needed immediately; rather it is used to combine adenosine
diphosphate (ADP) with another phosphate to form adenosine triphosphate (ATP)
molecules. The ATP can then be used for processes in the cells that require energy, much as
a battery powers a mechanical device. The formula for cellular respiration is:
(reactants)
(products)
C6H12O6 + O2  CO2 + H2O + Energy (ATP)
In order for respiration to occur, the mitochondria needs glucose (C₆H₁₂O₆) and oxygen
(O₂). This process then produces carbon dioxide (CO₂), water (H₂O), and cellular energy in
the form of ATP. Animals release this carbon dioxide while exhaling during the breathing
process. The inhalation of oxygen and exhalation of carbon dioxide is control by the
respiratory system. The carbon dioxide that is given off during the process of cellular
respiration can then be used by plants during photosynthesis to form new carbohydrates.
11. What happens to carbohydrates during cellular respiration? ________________________________
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12. What is the chemical energy in the cell called? _________
13. What do cells use ATP for? __________________________________________________________
14. What is a good analogy (similar comparison) for ATP? ____________________________________
15. What is needed for respiration to begin? ________________________________________________
16. What is produced by cellular respiration? _______________________________________________
17. How do animals get rid of the carbon dioxide? ______________________________
18. What body system is involved with removing this waste? __________________________
19. Fill out the chart below comparing the processes of photosynthesis and cellular respiration:
PROCESS
WHAT IS
NEEDED
WHAT IS
PRODUCED
LOCATION
PHOTOSYNTHESIS
CELLULAR
RESPIRATION
20. Explain the relationship between photosynthesis and cellular respiration. Be sure to include the main
purpose of both and where they occur inside the cell.
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