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Bio 100 Lecture 8
Energy for organisms
 Plants
 Animals
How do cells get energy for work?
 Cellular respiration
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Bio 100 Lecture 8
Cells use energy released in exergonic reactions to fuel endergonic reactions
(Energy coupling)
Adenosine triphosphate (has 3 phosphate groups)
 ATP has high potential energy

Glucose + O2 ➞ CO2 + H2O + ATP
Redox Reactions
Because an electron transfer requires a donor and an acceptor, oxidation and
reduction always go together.
Transfer of Electrons
An important player in the process of oxidizing glucose is a coenzyme called NAD+
and FAD+ which
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Bio 100 Lecture 8
Oxidized (missing an H) form– NAD+/FAD+
Reduced (gained an H) form – NADH/FADH
Electron Transport Chain
Stages of Cellular Respiration
1. Glycolysis
Without oxygen – Fermentation
With oxygen – Cellular Respiration
The pyruvate formed in glycolysis is transported from the cytoplasm into a
mitochondrion where the citric acid cycle and oxidative phosphorylation will
occur.
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Bio 100 Lecture 8
Energy banked so far (stored in ATP):
Glycolysis
2 NADH
2 ATP
Pyruvate Oxidation
2 NADH
2. Citric Acid/Krebs Cycle
2 ATP,
6 NADH
2 FADH2
Energy banked so far:
Glycolysis
2 NADH
2 ATP
Pyruvate Oxidation
2 NADH
Citric Acid Cycle
2 ATP
6 NADH
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Bio 100 Lecture 8
2 FADH2
Total:
10 NADH, 2 FADH2, 4 ATP
3. Oxidative phosphorylation
How is ATP produced?
Overview of Cellular Respiration:
1. Glycolysis
a. In the cytoplasm
b. Breaks glucose into two pyruvate molecules
2. Pyruvate oxidation
a. Readies pyruvate for citric acid cycle
b. Makes Acetyl CoA
3. Citric Acid Cycle
a. Occurs in mitochondria
b. Produces CO2
c. Supplies electrons to the next stage through NADH and FADH2
4. Oxidative Phosphorylation
a. Occurs in the cristae of mitochondrial inner membrane
b. Transfers electrons to oxygen
c. Energy released fuels H+ pumps
d. Chemiosomosis of H+ drives ATP synthase
How does food become fuel?
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Bio 100 Lecture 8
Food is broken down by enzymes into molecules that can enter cellular
respiration at some step.
Study Questions
1. What is needed for cellular respiration?
2. What molecule powers the cell?
3. What is the main storage of energy in the cell?
4. In a redox reaction if a H+ is lost is this reduced or oxidized?
5. What is the first step of cellular respiration and what is produced?
6. What is the second step?
7. How many ATP are produced through cellular respiration?