ACTIVITY 9.2: Modeling cellular respiration: How can cells convert the energy in glucose into ATP?
Draw the overall process of cellular respiration starting with glucose and ending up with ATP production in the
mitochondria. Include the steps of glycolysis, the citric acid cycle and oxidative phosphorylation
Be sure to include the following in your pathway:
Glucose
O2
CO2
Pyruvate
Acetyl coA
NAD+
NADH
FAD
FADH2
ADP and Pi
ATP
Water
Electron transport chain complexes I  IV
Mitochondria and its membranes, cristae and matrix
H+ and H+ gradients
Electrons (e-)
Chemiosmosis & Oxidative phosphorylation
ATP synthase
Substrate level phosphorylation
Use your pathway diagram to answer the following:
1. The summary formula for cellular respiration is
C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat)
At what stage(s) in the overall process is each
of the reactants used?
C6H12O6
6 O2
At what stage(s) in the overall process is each of the products
produced?
6 CO2
6 H2O
Energy
Glycolysis
Transition
Kreb’s
Electron transport chain
(ETC)
ETC
Glycolysis – ATP
Kreb’s – ATP
ETC - ATP
2. In cellular respiration, the oxidation of glucose is carried out in a controlled series of reactions. At each step or
reaction, a small amount of the total energy produced is released. Some of this energy is lost as heat but the rest
is converted into other forms that can be used by the cell to make ATP or to drive an endergonic reaction
What is/are the overall function(s)
of glycolysis?
What is/are the overall function(s) of
the Kreb’s Cycle
What is/are the overall
function(s) of oxidative
phosphorylation?
Production of:
1. Pyruvate (2)
2. ATP (2)
3. NADH (2)
4. CO2 (2) (transition step)
5. NADH (2) (transition step)
Production of:
1. ATP (2)
2. NADH (6)
3. FADH2 (2)
4. CO2 (4)
Production of:
1. ATP (32)
2. H20
3.
Are the components listed here
USED or PRODUCED in:
Glucose
Glycolysis?
The Kreb’s Cycle?
used
O2
used
CO2
produced
H20
produced
ATP
used & produced
ADP + Pi
NADH
NAD
Oxidative
phosphorylation?
produced
produced
produced
used
produced
produced
4. If the Kreb’s cycle does not require O2, why does cellular respiration stop after glycolysis when no O2 is
present?
The ETC creates a H+ gradient which allows for the import of pyruvate into the mitochondria – i.e. the H+ gradient
drives the import of pyruvate that happens during the transition step
5. How efficient is fermentation vs. aerobic/cellular respiration. Efficiency is the amount of useful energy (as
ATP) gained during the process divided by the total energy available in glucose. Use 686 kcal as the total
energy available in 1 mole of glucose and 8 kcal as the energy available in 1 mole of ATP
Efficiency in fermentation
2 ATP during glycolysis x 7.3 = 14. 6 kcal of energy
14.6/686 = 2% efficiency
Efficiency in cellular respiration
36 ATP made ( including glycolysis) x 7.3 = 263
kcal/mole
263/686 = 38% efficiency
32 from ETC x 7.3 = 234 kcal/mole
234/686 = 34% efficiency
6. Mitochondria isolated from liver cells can be used to study the rate of electron transport in response to a
variety of chemicals. The rate of electron transport is measured as the rate of disappearance of O2 from the
solution using an oxygen-sensitive electrode. How can we justify using the disappearance of O2 from the
solution as a measure of electron transport?
O2 is the ultimate electron acceptor in the ETC
7. An active college-age athlete can burn more than 3,000 kcal/day in exercise.
a. If conversion of one mole of ATP  ADP + Pi releases about 7.3 kcal, how many moles of ATP need to be
produced per day in order for this energy need to be met?
b. If the molecular weight of ATP is 573, how much would the required ATP weigh in kilograms?
c. Calculate and explain your results below
a. 3000/7.3 = 411 moles of ATP
b. 411 X 573 = 235,503 g = 235 kg