Cellular Respiration Packet
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Preview
Cellular Respiration: Breaking down Energy
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 cell 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 process happens in the mitochondria?
2. What is the purpose of the process in #1 (what does it create)?
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.
3. Some organisms perform photosynthesis to produce energy. Other organisms cannot do photosynthesis.
What can they do in order to generate energy?______________________________________________________
______________________________________________________________________________
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4. Animals and other organisms obtain the energy available in carbohydrates through the process of cellular
respiration. What is the purpose of cellular respiration? _________________________________________
______________________________________________________________________________________________________________________
______________________________________
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. During the process of cellular respiration, carbon dioxide is given off. Plant cells
can use this carbon dioxide during photosynthesis to form new carbohydrates.
5. What happens to carbohydrates during cellular respiration? _____________________________________
______________________________________________________________________________________________________________________
______________________________________
6. What is the chemical energy in the cell called? _________
7. What does ATP stand for? ________________________________________________________
8. What is one product of cellular respiration? ________________
9. How do animals get rid of the carbon dioxide? ______________________________
10. What body system is involved with removing this waste? __________________________
Also in the process of cellular respiration, oxygen gas is required to serve as an acceptor of electrons. This
oxygen is identical to the oxygen gas given off during photosynthesis.
11. (Circle one) Oxygen is a
or released?)
PRODUCT
OR
REACTANT
of respiration? (In other words, is it needed
Energyproducing
process
Reaction
Location in cell
Photosynthesis
12. ______________________________________________
Chloroplast
Cellular
respiration
13. __________________________
Note Taking Guide
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What kind of organisms can get energy from eating food?
How is a calorie measured?
Why does the energy stored in each macromolecule different?
What is cellular respiration?
Write the cellular respiration equation.
What is required for cellular respiration?
What are the pathways called that require oxygen?
What are the pathways called that does not require oxygen?
There are 3 stages of cellular respiration. List those stages.
What happens during glycolysis?
What is the net gain of ATP after glycolysis?
What is the product of glycolysis?
Is glycolysis aerobic or anaerobic?
What happens during the Krebs cycle?
What is another name for the Krebs cycle?
How is acetyl-CoA made?
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How many times will 1 glucose molecule turn the Krebs cycle?
How many places in the Krebs cycle do electron carriers accept a pair of high-energy electrons?
What happens during the electron transport chain?
What happens every time 2 high-energy electrons are passed down the electron transport chain?
When hydrogen ions build up in the intermediate space, what charge does it have?
What structure is located in the membrane of the mitochondria that produces ATP in the electron transport chain?
How many molecules of ATP are produced at the end of cellular respiration?
Study
Cellular Respiration is a process in all eukaryotes that breaks down sugars and other carbon-based molecules to
make ATP when oxygen is present. Because cellular respiration needs oxygen, it is an Aerobic Process. In
eukaryotic cells, the aerobic parts of the process take place in mitochondria. The step that leads to cellular
respiration takes place in the cytoplasm and is anaerobic, which means it does not need oxygen.
The anaerobic process that leads to cellular respiration is called glycolysis. In Glycolysis, two ATP molecules are
used to split a molecule of glucose into 2 three-carbon molecules, which produces four ATP molecules. Glycolysis
yields a net increase of two ATP molecules. Then, if oxygen is available, the products of glycolysis are used in cellular
respiration. Cellular respiration takes place in two general stages, in two different parts of the mitochondria.

The Krebs cycle is a series of chemical reactions that further breaks down the three-carbon molecules from
glycolysis. The Krebs cycle takes place in the matrix, or interior space, of mitochondria. These chemical
reactions produce carbon dioxide, a small number of ATP molecules, and energy-carrying molecules that are
used in the second stage of cellular respiration.

An electron transport chain uses the energy-carrying molecules from the Krebs cycle to produce a large
number of ATP molecules. Water, which is released as a waste produce, is also formed. The electron
transport chain is in the inner mitochondrial membrane.
The overall simplified chemical equation for the cellular respiration process is:
C6H12O6 + 6O2  6CO2 + 6H2O
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1. What is cellular respiration?
2. What is glycolysis, and why is it an anaerobic process?
3. What happens in the Krebs cycle?
4. What is the function of the electron transport chain?
Cellular Respiration takes place in the mitochondria of eukaryotic cells. Before cellular respiration can occur,
glucose is broken down in a cell’s cytoplasm during an anaerobic process called glycolysis.

During glycolysis, two ATP molecules are used to split a glucose molecule into two three-carbon molecules
that eventually become molecules called pyruvate. Four molecules of ATP (a net increase of two ATP), and
two molecules of an energy-carrying molecules called NADH are formed.
When oxygen is available, the pyruvate and NADH are used for cellular respiration in the mitochondria. The first
part of cellular respiration, including the Krebs cycle, takes place in the mitochondrial matrix. The second part takes
place within and across the inner mitochondrial membrane.

Pyruvate is broken down and is linked to a molecule called Coenzyme A. This molecule enters the Krebs
cycle. In the Krebs cycle, carbon-based molecules are broken down and rearranged to produce NADH and
FADH, which are energy-carrying molecules, two molecules of ATP, and carbon dioxide waste.

Energized electrons are removed from NADH and FADH by proteins in the electron transport chain.
Hydrogen ions are pumped across the inner membrane, then flow through ATP synthase to produce ATP.
1. What happens during glycolysis?
2. Describe the first stage of cellular respiration in mitochondria.
3. What is the function of the electron transport chain in cellular respiration?
4. What are the overall reactants and products in cellular respiration?
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Practice
True or False
Write true if the statement is true or false if the statement is false.
_____ 1. Cellular respiration begins with an electron transport chain.
_____ 2. Cellular respiration that proceeds in the presence of oxygen is called aerobic respiration.
_____ 3. Cellular respiration occurs in the mitochondria.
_____ 4. Just like the chloroplast, the stroma separates the inner and outer membranes of the mitochondria.
_____ 5. The Krebs cycle comes after glycolysis, during cellular respiration.
_____ 6. Cellular respiration begins with the absorption of sunlight by the mitochondria photosystems.
_____ 7. ATP synthase pumps hydrogen ions back into the mitochondria matrix.
_____ 8. The first reaction of the Krebs cycle produces citric acid.
_____ 9. One molecule of glucose holds enough energy to produce up to 36 ATP.
_____ 10. The Krebs cycle produces four ATP.
_____ 11. Two NADPH are made during glycolysis.
Multiple Choice
Circle the letter of the correct choice.
1. Glycolysis
(a) uses 2 ATPs and makes 2 ATPs, 2 NADHs, and 2 pyruvates.
(b) uses 2 ATPs and makes 4 ATPs, 2 NADHs, and 2 pyruvates.
(c) uses 4 ATPs and makes 2 ATPs, 2 NADHs, and 2 pyruvates.
(d) uses 2 ATPs and makes 4 ATPs, 4 NADHs, and 2 pyruvates.
2. Cellular respiration in the presence of oxygen is called
(a)
(b)
(c)
(d)
anaerobic respiration.
glycolysis.
aerobic respiration.
oxygen respiration.
3. The correct order of stages of cellular respiration is
(a) glycolysis - the Calvin cycle - electron transport.
(b) the light reactions - glycolysis - the Krebs cycle.
(c) glycolysis - the Krebs cycle - electron transport.
(d) electron transport - glycolysis - the Krebs cycle.
4. Where are the electron transport chains of cellular respiration located?
(a) in the inner membrane of the mitochondrion
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(b) in the matrix of the mitochondrion
(c) in the intermembrane space of the mitochondrion
(d) in the outer membrane of the mitochondrion
5. The enzyme at the end of cellular respiration that produces ATP is:
(a)
(b)
(c)
(d)
hydrogen.
oxygen.
water.
ATP synthase.
6. The chemical formula of cellular respiration is
(a) 6CO2 + 6H2O → C6H12O6 + 6O2.
(b) C6H12O6 + O2 → CO2 + H2O.
(c)
CO2 + H2O → C6H12O6 + O2.
(d) C6H12O6 + 6O2 → 6CO2 + 6H2O.
7. The chemiosmotic gradient of cellular respiration is an
(a) ion gradient made by the pumping of hydrogen ions across the inner membrane using the energy
of electrons as they are transported down the electron transport chain.
(b) ion gradient made by the pumping of hydrogen ions across the outer membrane using the energy
of electrons as they are transported down the electron transport chain.
(c) ion gradient made by the pumping of oxygen ions across the inner membrane using the energy
of electrons as they are transported down the electron transport chain.
(d) ion gradient made by the diffusion of hydrogen ions across the inner membrane using the energy
of electrons as they are transported down the electron transport chain.
8. In the presence of oxygen, one glucose molecule has the energy to make up to
(a) 4 FADH.
(b) 12 NADH.
(c) 36 ATP.
(d) all of the above
Vocabulary
Match the vocabulary word with the proper definition.
Definitions
_____ 1. channel protein and enzyme that makes ATP
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_____ 2. also known as the Krebs cycle
_____ 3. end product of glycolysis
_____ 4. cellular respiration in the absence of oxygen
_____ 5. energy-carrying compound involved in stage I and stage II of cellular respiration
_____ 6. a greater concentration of hydrogen ions in the intermembrane space than in the mitochondrial matrix
_____ 7. stage II of cellular respiration
_____ 8. glucose splitting
_____ 9. stage III of cellular respiration
_____ 10. cellular respiration in the presence of oxygen
Terms
a.
aerobic respiration
b.
anaerobic respiration
c.
ATP synthase
d.
chemiosmotic gradient
e.
citric acid cycle
f.
electron transport chain
g.
glycolysis
h.
Krebs cycle
i.
NADH
j.
Pyruvate
Fill in the blank with the appropriate term.
1.
The reactions of cellular respiration can be grouped into three stages: ____________, the ____________ cycle,
and electron transport.
2.
Cellular respiration in the absence of oxygen is called ____________ respiration.
3.
The last two stages of cellular respiration occur in the ____________.
4.
Most of the ATP is produced in the ___________ stage of cellular respiration.
5.
During glycolysis, enzymes split a molecule of glucose into two molecules of ____________.
6.
During the Krebs cycle, energy is captured in molecules of ____________, ____________,and FADH.
7.
____________ is the molecule that enters the Krebs cycle.
8.
During glycolysis, ____________ molecules of ATP are used, and ____________ molecules of ATP are made.
9.
____________ is the enzyme that produces ATP during the final stage of cellular respiration.
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10.
In all three stages of aerobic respiration, up to ____________ molecules of ATP may be produced from a
single molecule of glucose.
Quiz
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