Cellular respiration involves three main stages - glycolysis, the citric acid cycle, and oxidative phosphorylation. Glycolysis breaks down glucose into pyruvate, producing a small amount of ATP. The citric acid cycle further oxidizes pyruvate and produces more ATP and reducing agents. During oxidative phosphorylation, ATP is extensively produced as electrons are transferred through an electron transport chain with oxygen as the final electron acceptor.

1. CONTENT STANDARD
The learners demonstrate a understanding of how organisms obtain and utilize energy
PERFORMANCE STANDARD
The learner shall be able to make a poster that shows the complementary relationship of
photosynthesis
and cellular respiration.
1. Let your students recall that energy from sunlight is transformed to chemical energy stored in
macromolecules such as sugars through the process of photosynthesis.
2. For this lesson inform your students that they will learn how the energy stored in sugars is used to
produce ATP which is the energy currency of the cell.
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Inquiry-based Activity 10 mins
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Inquiry-based Activity
1. Ask your students the following:
a. what they ate for breakfast or lunch
b. what activities they performed after eating breakfast or lunch
2. Let them recite their answers.
TI P
Lecture 135 mins
0 REMIXES
1. Discuss that cellular respiration is a catabolic pathway
a. Catabolic pathways – release energy by breaking down complex molecules to simpler
compounds; ex. glucose broken down to CO2 and H2O
2. Review what reduction – oxidation (redox) reactions are
a. Reduction – gain of electrons
b. Oxidation – loss of electrons

2. 3. You may use the following diagram:
4. Describe the nature of ATP. You may use the following diagram to do this.
5. Give examples of the different types of cell work which all require energy in the form of ATP
a. mechanical – beating of cilia; contraction of muscle cells; cytoplasmic flow
b. transport – active transport
c. chemical – synthesis of polymers from monomers
6. Give an overview of the three major stages of cellular respiration and mention that they should
occur in the given order.
a. Glycolysis is the breakdown of glucose to pyruvate where small amounts of ATP are produced.
This process occurs in the cytoplasm of the cell.
b. Citric acid cycle or tricarboxylic acid cycle or Krebs cycle degrades pyruvate to carbon dioxide,
water, ATP and reducing power in the form of NADH, H+. This stage happens in the matrix of the
mitochondria.
c. Oxidative phosphorylation which includes electron transport chain and chemiosmosis generates
high amounts of ATP. This stage occurs in the inner membrane of the mitochondria.
7. Discuss glycolysis in more detail
a. Describe the ten steps. You may also give the enzyme that catalyzes each step.
b. A molecule of six-carbon glucose is broken down into two molecules of three-carbon pyruvate.
c. Point out that ATP is required in the first and third steps for a total of 2 ATP.

3. d. Explain that for every glucose molecule that is broken down, four ATP molecules are produced via
substrate level phosphorylation. Two molecules are produced from step 7 and two more from step
10. The net ATP produced is 2.
e. Show that two molecules of NADH, H+ are produced from step 6.
8. Summarize glycolysis by showing this diagram:
9. Discuss citric acid cycle in more detail
a. Describe the oxidation and decarboxyation of pyruvate producing acetyl CoA and CO2. This
step also produces NADH, H+. For every pyruvate, one molecule of CO2, one molecule of acetyl
CoA and one molecule of NADH, H+ are produced.
b. Acetyl CoA enters the citric acid cycle. Describe the eight steps. You may also give the
enzyme that catalyzes each step.
c. Show that NADH, H+ are produced from steps 3, 4 and 8; FADH2 is produced from step 6 and
ATP from step 5.
d. Show that CO2 is released from steps 3 and 4.
e. Explain that for every acetyl CoA that enters the cycle, three molecules of NADH, H+, one
molecule of FADH2, one molecule of ATP, and two molecules of CO2 are produced.
10. Summarize citric acid cycle by showing this diagram:
11. Discuss oxidative phosphorylation in more detail
a. Describe the electron transport chain. Show that the electrons from the oxidation of NADH, H+
are passed from one electron carrier to another in the electron transport chain.
b. Emphasize that the NADH,H+ and FADH2 produced from the previous stages are the electron
donors in this stage and that the final electron acceptor is oxygen.
c. Describe that ATP is produced by ATP synthase via chemiosmosis.

4. d. Discuss that for every molecule of NADH, H+ which is oxidized via oxidative phosphorylation,
three molecules of ATP are produced and that for every molecule of FADH2, two molecules of A
12. Summarize cellular respiration by discussing its general equation:
The six-carbon sugar such as glucose is oxidized and oxygen is reduced forming carbon dioxide,
water and energy.
13.Discuss the relationship of photosynthesis and cellular respiration. You may use the following
diagram to emphasize the relationship of these two major cellular processes.
14. The cellular respiration process that has so far been discussed involves oxygen, thus it is also
referred to as aerobic respiration. But you may also discuss that some cells are capable of producing
ATP in the absence of oxygen through fermentation or anaerobic respiration.
There are two types of fermentation process:
a. ethanol fermentation – pyruvate from glycolysis loses carbon dioxide and is converted to
twocarbon compound acetaldehyde which is then reduced to ethanol; this step also produces
NADH, H +. Wine is produced by some bacteria through this process.
b. lactic acid fermentation – pyruvate from glycolysis is reduced to lactate coupled with the
oxidation of NADH, H+. When oxygen is scarce, human muscle cells may switch to anaerobic
respiration leading to the accumulation of lactate.
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Class Presentation 45 mins
0 REMIXES
Class Presentation

5. 1.Divide the class into three groups. Assign (or draw lots) the three major stages to each group.
Each group will have a discussion and has to think of an analogy of the stage assigned to them. The
analogy could be like an everyday story. It could be a story of love, friendship, family, war, peace or
even of current events.
2.Ask your students to present their analogy/story to the class for five minutes each group. They
should indicate how the story is parallel or analogous to the stage of cellular respiration.
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Quiz 40 mins
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Quiz
Here are sample questions on this topic:
1. The following are the different stages of cellular respiration except
A. Calvin cycle
B. citric acid cycle
C. glycolysis
D. oxidative phosphorylation
E. oxidation and decarboxylation of acetyl CoA
2. The following is(are) true of glycolysis
A. Glycolysis is the breakdown of six-carbon glucose to two molecules of three-carbon pyruvate.
B. Glycolysis produces a net total of four molecules of ATP via substrate level phosphorylation
and two molecules of NADH,H+.
C. Glycolysis occurs in the mitochondrial matrix.
D. A and B are correct.
E. A, B, and C are correct.

6. 3. Citric acid cycle produces
A. ATP
B. NADH, H+
C. CO2
D. A and B only
E. A, B, and C
4. The electron donor(s) during oxidative phosphorylation is(are)
A. ATP
B. FADH2
C. NADH, H+
D. A and B
E. B and C
5. The final electron acceptor during oxidative phosphorylation is
A. AATP
B. carbon dioxide
C. oxygen
D. NADH, H+
E. FADH2
6. ATP as the energy currency of the cell is used in the following

7. A. synthesis of polymers from monomers
B. active transport
C. beating of cilia
D. contraction of muscle cells
E. all of the above