Name ____________________________________________
Ms. Boehm
Date _____________
Block ___________
Cellular Respiration Packet
Introduction:
Cells need energy to survive and do work. Cell “work involves things such as movement, making new
molecules, cell reproduction, etc. Nearly all cells get their energy from such carbohydrates as starches and
sugars. These compounds are first digested, or broken down, into glucose that can diffuse into cells. Inside
cells, glucose molecules are taken apart. The energy stored in the chemical bonds of glucose is released
gradually. The energy is stored in a special energy-carrier compound. The stored energy is then available for
later use by the cell.
1. Where do cells get their energy?
2. What small molecules are linked together to form starch? (This is a recall question. The answer is not in the
paragraph above)
ATP & Respiration:
The process of breaking molecules apart to release energy is called cell respiration. During cell
respiration the energy in glucose is released. This energy is stored in energy carrier molecules called Adenosine
Triphosphate, or ATP. When the cell needs this energy, ATP is changed to a molecule called Adenosine
Diphosphate, or ADP. This reaction (ATP  ADP) releases energy for the cell to use. In the next activity you
will learn more about the ATP molecule.
Constructing an ATP molecule:
An ATP (adenosine triphosphate) molecule is made up of 1 ribose molecule, 1 adenine molecule, and 3
phosphate groups.
3. What does the prefix “tri-“ in triphosphate mean?
Detach the last sheet of paper in this packet and locate Figure 1. You will need a pair of scissors and some
colored pencils for this portion of the activity.
 Color the model of adenine yellow, the ribose green, and the phosphate groups blue.
 Cut out the models of adenine, ribose, and phosphate group you have just colored. Be sure you cut
along the solid lines only.
 Attempt to join the adenine and ribose molecules together as you would join puzzle pieces.
4. What end parts must first be removed from each molecule in order for adenine and ribose to fit together?

Remove these parts. The adenine and ribose molecules can now be chemically joined. New points of
attachment or chemical bonds are formed.
5. What molecule can be formed from the parts you removed from the adenine and ribose?



Examine the phosphate group molecule
Attach one of the 3 phosphate groups to the ribose molecule by removing an H from the phosphate
group molecule and an OH from the ribose
Attach the remaining phosphate groups one at a time to the phosphate group already attached to the
ribose.
6. What did you have to remove to make these connections?
You have now built an ATP molecule
7. List the 5 “building blocks” that are needed to form an ATP molecule:
VERY IMPORTANT – READ THIS: The process of adding phosphate groups onto the ribose takes energy.
In the cell this energy comes from the breakdown of glucose. The cell actually stores some of its energy in the
ATP molecule.
Gaining Energy from ATP as it changes to ADP:
When the cell needs to use some of the stored energy it breaks a phosphate group off of the ATP
molecule. The process of breaking the phosphate group off the ATP molecule releases energy.
 Remove one phosphate group from the end of your ATP molecule
8. How many phosphate groups are still attached to the original molecule?
9. This new compound with one fewer phosphate groups than before is call Adenosine Diphosphate (ADP).
What does the prefix “di-“ mean?
10. List the “building blocks” that are needed to form 1 molecule of ADP:
11. Explain how an ATP molecule is changed into an ADP molecule:
Changing ADP to ATP:
VERY IMPORTANT – READ THIS AGAIN: The process of adding phosphate groups onto the ribose takes
energy. In the cell this energy comes from the breakdown of glucose. The cell actually stores some of its
energy in the ATP molecule. To be more accurate we can say that this energy is stored in the bond that holds
the phosphate group onto the ATP molecule.
 Construct an ADP molecule (or use the one you have from before)
 Attach a phosphate group to the ADP model. This forms an ATP molecule. In the cell this would
require energy and this energy comes from the breakdown of glucose.
 Using a type of shorthand, this change can be written as follows:
ADP + phosphate group + E  ATP
12. What might the letter E in the above equation be an abbreviation for?

Tape your completed ATP molecule in the space below:
Cellular Respiration:
Definitions:
o Aerobic – requires oxygen
o Anaerobic – no oxygen required
In the previous activity you learned how the cell can make an energy carrier, known as ATP. You also
learned that it takes energy to make this molecule. In this part you will learn how the cell gets that precious
energy from the glucose molecule so it can store it in the ATP molecule. The process of cellular respiration can
be divided into 3 stages: Glycolysis, Kreb’s Cycle, and the Electron Transport Chain.
Glycolysis
The first steps in cell respiration, or glycolysis, occur in the cytoplasm.
They can take place with or without oxygen, therefore, they are considered
anaerobic. The glucose molecule is broken down into 2 molecules of pyruvate
as shown in Figure 2. Two molecules of ATP are produced from ADP and
P (phosphate) along the way. What happens next depends on whether or not
oxygen is present.
Kreb’s Cycle & Electron Transport Chain
Most cells complete the breakdown of glucose in the presence of oxygen.
This process is called aerobic respiration and includes stages called the Kreb’s
Cycle and the Electron Transport Chain. In this series of reactions, pyruvate is
converted to carbon dioxide and water as shown in Figure 3. An additional 34
molecules of ATP are eventually formed from products of these reactions.
We can write a chemical equation to show what happens during cellular respiration:
36 ADP + 36 P + C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP
The part of cellular respiration that occurs after glycolysis actually occurs in a series of reactions, each
requiring a specific enzyme. These processes, which includes a complex series of reactions called the Kreb’s
Cycle and the Electron Transport Chain, require oxygen. These reactions take place in the mitochondria. Once
the reactions are complete the mitochondria releases the ATP, water and carbon dioxide into the cytoplasm.
Fermentation
In some cases, the breakdown of glucose is completed without using oxygen
in a process known as fermentation. In this process, pyruvate is converted to carbon
dioxide and either alcohol or lactic acid (as shown in Figure 4). No additional
energy is produced. Therefore, the total energy yield from the breakdown of a
molecule of glucose in the absence of oxygen is the 2 molecules of ATP produced
during glycolysis. Compared to aerobic respiration, fermentation is relatively
inefficient.
Some organisms, such as bacteria, obtain all of their energy from fermentation.
There are a variety of commercial uses for these bacteria. Production of wine and beer
depend on the alcohol that is formed during fermentation. Some cells, such as muscle
cells, revert to fermentation when oxygen is in short supply, such as during intense exercise. When the
bloodstream cannot supply oxygen to muscle cells fast enough, the muscle cells begin producing energy without
oxygen. The product of this is lactic acid, which is the reason your muscle can ache the day after strenuous
exercise.
13. Where, in the cell, does glycolysis occur?
14. What is cellular respiration?
15. Examine the chemical equation on the previous page. Rewrite it using words instead of symbols.
16. When glucose is broken down, energy is released. Where does that energy end up?
17. Find a picture of a mitochondria organelle, either in your book or from your notes. Use the space below to
draw a mitochondria organelle. Include and label the following parts: Outer membrane, Inner membrane,
Cristae, & Matrix.
18. How do ADP and ATP differ in the:
o number of phosphate groups? _____________________________________________________
o number of ribose molecules? _____________________________________________________
o number of adenine molecules? ____________________________________________________
19. Why do you think you could run faster, jump higher, etc if you could get more oxygen to your muscle cells
during strenuous exercise?
20. How is energy stored and released by ATP?
21. How do cells use the energy released from ATP?