Cell Respiration Guided Notes
We will complete the following tutorial detailing cell respiration:
http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
1. What is the overall purpose of cell respiration?
2. What kinds of organisms perform cell respiration?
3. Complete the following chart for the inputs and outputs of respiration:
Inputs
Outputs
4. From the inputs and outputs above, write the overall equation for cell respiration:
5. Compare the equations for cell respiration and photosynthesis in terms of:
a. Inputs:
b. Outputs:
c. Energy required/produced:
d. Although not listed in the video, compare which types of organisms undergo:
i. Respiration:
ii. Photosynthesis
6. What are the three major steps of cellular respiration?
a.
b.
c.
Glycolysis
1. What is the POINT of glycolysis?
2. Where does glycolysis take place in the cell?
3. How does glycolysis fit into the process of cell respiration for many organisms?
4. What are the phases of glycolysis?
a.
b.
5. How does the metaphor of a bicyclist compare to the two phases of glycolysis? How
does this compare to the activation energy needed in exergonic chemical reactions?
6. Investment phase
a. What is the input in glycolysis that allows for the breakdown of glucose?
b. What is the result of phosphorylating the glucose molecule in glycolysis?
7. Payoff phase
a. What is the effect of adding additional phosphates to the broken-down
glucose?
b. What is transferred from the broken-down glucose to NAD+? What will these
products will be used for later?
c. Compare NAD+ and NADH in terms of their oxidation and reduction states
and in terms of the amount of energy each carries.
d. What is generated by the addition of phosphates?
e. What else is generated in glycolysis?
f. Which molecules are the broken-down glucoses converted to?
8. ATP Yield
a. How much ATP is invested in glycolysis?
b. How much is produced total?
c. What is the NET ATP production in glycolysis?
d. In the last steps of glycolysis, where did the P come from to make ATP? This
process is known as ‘substrate-level phosophorylation.’ Based on your
observations, define substrate-level phosphorylation:
Summarize glycolysis below:
Inputs
Outputs
From the inputs and outputs above, write an equation for glycolysis below:
What is the net energy yield from glycolysis?
ATP
Electron Carriers
9. Glycolysis summarization and reflection:
a. Glycolysis literally means ‘breaking sugar.’ If glucose is C6H12O6, and no
carbons have been lost, how many carbons are likely found in each pyruvate?
b. Why don’t most organisms end cell respiration with glycolysis?
c. Glycolysis takes place in the cytoplasm, whereas the rest of aerobic cell
respiration (Krebs Cycle; ETC) takes place in mitochondria in eukaryotes and
in specialized infoldings of the cell membrane in prokaryotes. Which do you
think evolved first: glycolysis or the Krebs Cycle and ETC? Why?
d. The enzyme phosphofructokinase is an allosteric enzyme that is regulated by
products produced from glycolysis, the citric acid cycle, and oxidative
phosphorylation. Considering the overall result of glycolysis, would you
expect an excess of ATP to stimulate or inhibit the activity of this enzyme?
What type of feedback cycle would this be considered? Explain
Krebs Cycle
1. What do pyruvate molecules retain from glucose?
2. Where does glycolysis take place? Where does the Krebs cycle take place?
3. How is pyruvate modified so that it can be transported into mitochondria?
a. Production of CO2
b. Modification with Coenzyme-A
c. Reduction of NAD+
What are the inputs and outputs of the modification (oxidation) of pyruvate?
How many acetyl-CoA, CO2 and NADH molecules are produced per molecule of pyruvate?
Per initial molecule of glucose?
Inputs
Outputs
From the inputs and outputs above, write an equation for the oxidation of pyruvate below:
What is the net energy yield from the oxidation of pyruvate?
ATP
Electron Carriers
Label the following to show the oxidation of pyruvate to acetyle-CoA.
Krebs Cycle (aka The Citric Acid Cycle)
1. What is the acetyl-CoA added to? How many carbons are in acetyl-CoA? In OAA? In
the newly formed molecule?
2. What happens to the 6-carbon molecule using water?
3. How is CO2 produced? What ultimately happens to that CO2?
4. What is produced along with CO2?
5. How is ATP formed during the Krebs cycle?
6. How is FADH2 formed during the Krebs cycle?
7. How else is NADH produced?
8. What is regenerated at the end of the Krebs cycle?
9. What happens when the cycle repeats? Why is the cycle repeated?
10. What is the fate of all the carbons in the original glucose by the end of the second
round of the Krebs cycle?
11. What happens to the reduced electron carriers following the Krebs cycle?
12. What does the ETC produce large amounts of?
13. What does the Krebs Cycle and ETC depend on? What happens if this is not present?
14. What is the benefit of producing more mitochondria in muscle cells?
List the inputs and outputs of the Krebs Cycle below.
Inputs
Outputs
From the inputs and outputs above, write an equation for the Krebs Cycle below:
What is the net energy yield from the Krebs Cycle?
ATP
Electron Carriers
15. ATP Yield
a. What is the net ATP production in the Krebs Cycle?
b. In the ATP-producing steps of the Krebs Cycle, where did the P come from to
make ATP? This process is known as ‘substrate-level phosophorylation.’
Based on your observations, define substrate-level phosphorylation:
16. Oxidation of Pyruvate and Krebs Cycle summarization and reflection:
a. At the end of glycolysis, much of the potential energy from glucose remained
in the carbon-carbon bonds of the pyruvates. What happened to that
potential energy? Which molecules was it transferred to?
b. The oxidation of pyruvate and acetyl-CoA to CO2 is accompanied by the
reduction of which molecules?
c. The Krebs Cycle is a cycle that begins with the addition of a two-carbon
compound (Co-A) to a four-carbon one (OAA) to form citric acid. (Citric acid
may be called citrate in your books. It’s functionally the same.) Describe how
carbons are added, then removed, and how the cycle regenerates its starting
material. You do NOT need to know the names of each compound or the
enzymes in the cycle!
d. Glycolysis is present in almost all organisms, whereas the Krebs (Citric Acid
Cycle) and ETC are present only in organisms that perform aerobic
respiration. Which process likely evolved first: glycolysis or the Krebs/ETC?
What is the likely benefit of performing the Krebs/ETC over simply splitting
glucose into pyruvate?
Electron Transport Chain and Chemiosmosis
1. What is the POINT of the ETC?
2. How does the ATP production in the ETC compare to that of glycolysis and the Krebs
Cycle?
3. What is the energy from the electrons used for the in the electron transport chain?
Fill in the following blanks using the following terms: Electrons, proteins, energy,
protons: Using the __________ of ___________ to make ____________ pump __________.
4. How is a concentration gradient of protons formed?
5. Based on concentration, where do the protons ‘want’ to diffuse to? Based on charge,
where do the protons want to diffuse to?
6. What is the role of oxygen in the electron transport chain? What is the term for
oxygen being ‘electron greedy’?
7. If electrons are being added to oxygen, what else must be added to oxygen in the
reduction reaction? What would this form?
8. What is the diffusion of protons through a membrane protein (ATP Synthase) used
to power?
The following diagram is of H+ ions moving through a protein to power the formation of
ATP from ADP and Pi. Label the diagram.
9. This diffusion of protons is also called chemiosmosis. Based on word roots and prior
knowledge, why is this called chemiosmosis?
10. The diagram on the next page offers an in-depth diagram of what is going on during
the ETC and chemiosmosis. It may help to color-code the diagram or, using
manipulatives, model what is happening during these processes. Label each part of
the diagram and sequence what is happening!
11. What is the effect of a lack of oxygen on the ETC?
12. Where do the oxidized NAD+ go once they have delivered electrons and hydrogen to
the ETC? (Note: You can stop this animation at 3:28.)
List the inputs and outputs of the ETC below.
Inputs
Outputs
From the inputs and outputs above, write an equation for the ETC below:
What is the net energy yield from the ETC?
For each NADH produced during glycolysis, oxidation of pyruvate and the Krebs
Cycle, three ATP can be produced. For each FADH2 produced in the Krebs Cycle two
ATP can be produced.
ATP
17. ATP Yield
a. What is the net ATP production in the ETC?
b. In the ATP-producing steps of the ETC, how is ATP produced? This is known
as oxidative phosphorylation. What is being oxidized in the ETC to power the
phosphorylation of ATP?
c. Compare the ATP yield of the ETC with that of the Krebs Cycle and glycolysis.
Why is performing the ETC energetically advantageous?
Cellular Respiration: An Overview
1. What forms of energy does the energy in glucose take during respiration?


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2. Summarize the overall process of cell respiration on the diagram below.
3. Summarization and Reflection
a. During cell respiration, glucose is oxidized to carbon dioxide, electrons and
hydrogens. Write this as a half-reaction:

b. During cell respiration, oxygen is reduced to water. Write this as an equation.
Remember what must be added to oxygen to produce a half-reaction!

c. What would be the effect hypoxia/anoxia on aerobic respiration? Many
organisms can become what is known as ‘facultative’ anaerobes – meaning
they switch to an alternative form of respiration such as fermentation in lowoxygen environments. At which point in cell respiration would it be most
advantageous to switch to an alternative form of respiration? Why?
d. Imagine if an irreversible inhibitor bound to cytochrome oxidase and
prevented oxygen from receiving electrons from the ETC. What effect would
this have on the ATP levels in an organism? Explain!