WWLPT Biology Institute: Motion
Electron Transport System Made
Fun and Easy:
The Movement to ATP Energy
This activity corresponds with the following National Science Education
Standards: Content Standards A, C, and G;
Teaching Standard A; Assessment Standards A
Recognize and analyze alternative explanations and models (A); developing
student understanding including the cell and matter, energy, and organization
in living systems (C); historical perspectives (G)
Select science content and adapt and design curricula to meet the interests,
knowledge, understanding, abilities, and experiences of students (A)
Authentic assessment opportunities (A)
Target Age or Ability Group Audience
Materials & Equipment Needs
Background [Prior Knowledge
or vocabulary necessary to complete activity]
The Student Role Play
Method of Evaluation/Assessment
Science Education Standards
Cell respiration is a fundamental function of aerobic organisms.
The concepts of glycolysis, Krebs cycle and electron transport system (oxidative
phosphorylation) are important yet challenging. The example for role
playing electron transport provides both the principles and chemical activities.
Students will be able to:
identity the components of electron transport system through role play.
explain the role of intermediate energy carriers to the production of ATP
describe the relationship of electron transport system to Krebs Cycle and
glycolysis as it relates to cellular respiration.
anaylze the understanding of cellular respiration to other types of mechanisms
for obtaining energy.
Target Audience or Age Group
Grades 9 - 12: Biological courses
Notes to the Teacher:
The use of biology coloring book illustrations are helpful when explaining
or modeling the steps for cellular respiration.
Another resource which reinforces the concepts of glycolysis, oxidative
decarboxylation, Krebs cycle and electron transport is the video
series "Cellular Respiration". Video tapes are in 10 minute segments
to compliment instruction. http://188.8.131.52/kn/itv/cellular.sht
The diagram below is a suggested setup for the classroom to role play the
electron transport system component:
Materials & Equipment
Needs to top
Two-Sided Signs (as many as needed)
ATP/ADP + P
4 tennis balls (electrons)
Five rows of chairs or desks
Teacher workstation or desk
~26-28 balloons with ribbon (tie balloon pairs together by color,
i.e., blue, green)
I.Metabolism - sum of all chemical reactions
Cell Respiration Overview
- involves everything to produce "life"
A.Catabolism - all reactions that break large molecules down
into smaller ones to trap the energy from them.
1. Example: simple organic molecule (like glucose)
---> breaks down to C02 + H20 + small "inorganic"
molecule + chemical
energy (ATP) + heat energy
2.Cell respiration - example of catabolism
- stepwise oxidation (loss of electrons) of high energy food molecules
to low energy molecules + C02 +
H2O such as:
C6 H1206 (glucose) + 02
---> C02 + H2O + energy
-glucose breakdown into eventually two pyruvic acids (pyruvate) occurs
in cytoplasm of cell some amino acids can be
broken down by this pathway after amino (NH2) groups are removed
--- > gets converted into one or another of
the intermediate compounds which eventually gets oxidized in the same way
- pyruvate (pyruvic acid) gets converted to acetyl coenzyme A
- occurs in the matrix of mitachandria
c.Krebs Cycle (Citric Acid
Cycle or (TCA cycle) Tricarboxylic acid)
- series of catabolic reactions metabolizing pyruvate into intermediate
energy carriers (NADH2 and FADH2) + C02
d.Electron Transport System
-final process of converting intermediate energy carriers (NADH2
and FADH2) into lots of ATP
-02 is needed (at this point) to pick up a pair of electrons
to form H2O
Chart for the comparison of aerobic and anaerobic catabolism.
B.Anabolism - uses chemical energy (ATP) to recombine simple
organic molecules into complex organic molecules
1. Complex molecules such as: proteins, carbohydrates,
lipids, DNA, etc.
2. FADH2 passes 2 H+ + 2 electrons to ETS.
Cell Respiration Steps
I. GLYCOLYSIS (occurs in cellular cytoplasm or cytosol)
Glucose + enzyme 1 --- >glucose 6-phosphate
+enzyme 2 --- > fructose 6-phosphate
(unstable and wants to revert)
Reaction coupling - an ATP immediately enters
to prevent fructose 6-phosphate from reverting to
+ enzyme 3 --- > fructose diphosphate
+ enzyme 4 --- >cleaves into DHAP + PGAL
--- >the DHAP + enzyme 5--->
forms another PGAL
(The 2 PGAL have a higher energy potential than the original 6-carbon glucose
molecule. From this
(3 carbon) point, every molecule
is in duplicate.)
Next, the 2 PGAL + enzyme 6--- > 2
DPGA (diphosphoglycerate) + enzyme 7--->
(NADH2 is an intermediate energy carrier which is used to generate
ATP later in
the process. The electron deficient NAD+ tends to snap
up a pair of electrons plus
H+ from the oxidation of PGAL to DPGA. Then, the NADH2
goes to the ETS.)
2 3-PGA (3-phosphoglycerate) + enzyme 8
to> 2 2- PGA
(2-phosphoglycerate) + enzyme 9 --->
2 PEP (phosphoenol pyruvate) + enzyme 10 ---
> 2 pyruvate or pyruvic acid (3-C molecule)
Three ways that pyruvate can be possibly directed: 1) ethanol + CO2
(fermentation), 2) lactic acid (anaerobic), or
3) cell respiration (aerobic).
INTERMEDIATE STEP - OXIDATIVE DECARBOXYLATION
(This process is the breakdown of pyruvate. Pyruvate moves from the
cytoplasm into the mitochondrial matrix. The following is the AEROBIC
2 pyruvate + enzyme 11 ---> 2
acetyl CoA (2 carbon)---> goes
to the Krebs Cycle
II. KREBS CYCLE (or Citric Acid Cycle or TCA Cycle-Tricarboxylic Acid)
(Double the molecules made in this pathway)
Step 1: acetyl Co A (2 carbon) + oxyaloacetate (4 carbon) + enzyme
Step 2: citric acid + enzyme --->
Step 3: aconitate + water molecule + enzyme
Step 4: isocitrate + enzyme --->
Step 5: oxalosuccinate + enzyme --->
Step 6: ketoglutarate + enzyme + Coenzyme A-SH
Step 7: succinyl Co A + enzyme --->
Step 8: succinate + enzyme --->
(Another kind of intermediate energy carrier which will make more ATP in
Step 9: fumarate + enzyme --->
Step 10: malate + enzyme --->
Then, back to oxaloacetate...
III. ELECTRON TRANSPORT SYSTEM (ETS or Oxidative Phosphorylation)
Background: There is an accumulation of 10 NADH2 and 2 FADH2
in the mitochondrial matrix from the previous steps. ETS occurs in the
1. NADH2 passes 2 H+ + 2 electrons to ETS.
a) 2 electrons make three trips through the cristae membrane dropping off
3 pairs of protons (H+) into the intermembrane space.
b) Each NADH2 will produce 3 ATP's, ultimately.
a) 2 electrons make two trips through the cristae membrane dropping
off 2 pairs of protons into the interrnembrane space.
b) Each FADH2 will produce 2 ATP's, ultimately.
3. At the end of the chain, the "spent" pair of electrons are accepted
by 1 oxygen atom and 2 protons (H+) which are from dissociated
water which will form a new water molecule.
a) Without oxygen (from breathing or ventilation), ETS would get backed
up with electrons. Consequently, no more energy could be obtained from
food via the cellular respiration pathway.
4. Energy is "stockpiled" in the form of a proton gradient found in
the intermembrane space as potential energy.
5. As result of the energy from the proton gradient, a pair of protons
moves back into the mitchondrial matrix through special protein channels
that are connected to ATP synthase enzymes. (See attached C&EN article)
The ATP synthase enzymes catalyze ADP + phosphate to form ATP.
a)ATP synthase + the proton gradient potential provide enough energy
to join ADP + P.
Total: 36 ATP from one glucose molecule
"Chemistry Nobel: Researchers from three countries share
prize for ATP synthase discoveries"
|NET GAINS OF:
2 (makes only 2 ATP per NADH2 in ETS)
|Electron Transport System
Borman, Stu. Chemistry and Engineering News. Oct. 20, 1997,
Three researchers received
word last week from the Royal Swedish Academy of Sciences that they had
won the world's most prestigious chemical honor---the 1997 Nobel Prize
One-half of this year's
$1 million prize is being shared by emeritus professor of Biochemistry,
Paul D. Boyer of the University of California. Los Angeles, and senior
scientist John E. Walker of the Medical Research Council Laboratory of
Molecular Biology, Cambridge, England. They are being honored for having
elucidated the enzymatic mechanism by which ATP synthase (ATPase) catalyzes
the synthesis of adenosine triphosphate (ATP), the energy currency of living
The other half of the prize
goes to emeritus professor of biophysics Jens C. Skou of Aarhus University,
Denmark, for his discovery, of the first molecular pump, an ion-transporting
enzyme called Na+-K+ ATPase.
In the late 1970"s, Boyer
proposed the "binding-change hypothesis," a detailed molecular mechanism
for the ATPase-catalyzed synthesis of ATP from adenosine diphosphate (ADP)
and inorganic phosphate in animall mitochondria, plant chloroplasts, and
bacterial cell membranes. Walker verified the mechanism by obtaining the
amino acid sequence of ATPase in the eariv 1980's and the first high-resolution
crystal structure of the enyzme's catalytic domain in 1994. "Walker's work
complements Boyer's in a remarkable manner," savs the academy.
Bover hypothesized that
ATPase's three catalytic sites pass through "loose", "tight," and "open"
conformational states in each of three catalytic cycles. In the first cycle,
ATP synthesis involves binding of ADP and phosphate to an active site in
the loose state, energy-driven conformational conversion of the site to
the tight state, and subsequent synthesis of ATP. ATP is actually
released in the enzyme's second catalytic cycle, when the site converts
from loose to open. In the enzyme's third catalytic cyccle, the site
reverts from open to loose, making it capable of binding substrate once
Walker's crystal structure
showed that at any one moment the conformations of each of ATPase's three
catalytic sites were different, a finding consistent with Boyer's model.
The structure also suggested a way that energy could be coupled to ATP
synthesis by relative rotation of the enzyme's domains. This has been come
out by subsequent research, including a recent study by a Japanese group
in which an ingenious technique was used to visualize the rotation process.
With his prize winnings,
Walker said, "I was thinking I'd buy myself a new bicycle"-a gift in keeping
with the theme of rotatory catalysis. Skou was honored for his discovery,
in the late 1950's, of Na+-K+ATPase, the first enzyme
found to promote directed transport through cell membranes. This specialized
ATPase maintains the proper balance of sodium and potassium ions across
membranes, consuming about one-third of all the ATP produced in the body
in the process. The energy stored in the ion gradients is used to drive
essential cell functions, such as nerve impulse transmission. Numerous
enzymes have since been demonstrated to have related similar functions---including
Ca2+ ATPase, which helps control muscle contraction, and Na+-K+ATPase,
which plays a key role in digestion.
The Student Role Play to
Introduction: Cellular Respiration is critical in aerobic organisms.
The process includes glycolysis, Kreb's cycle, and the electron transport
system. The electron transport system is the aspect of the cellular respiration
process that is the most dynamic in synthesizing ATP energy.
Purpose: The students will kinesthetically learn the electron transport
system (ETS) process.
Procedure: The teacher will model the process with several students,
initially. Then, the students will "act out" ETS. It is recommended
that students switch roles several times.
Observation: After the role play experience, each student will record
their understanding of ETS.
Conclusions: Students can share their findings with the class in the
more traditional fashion or using a cooperative learning strategy such
as "Think-Pair-Share" or "JigSaw". (Kagen)
Methods of Evaluation/Assessment
Each student or teams could summarize the ETS process in the form of a
poem, song, or rap. Have students design a rubric appropriate to the task.
Each student or teams could develop a game or three-dimensional (working,
possibily) model of ETS.
References Including Web Addresses
Kagen Cooperative Learning resource site.
Cellular respiration concept map.
Cellular respiration crossword puzzle.
Teaching aids on cellular respiration.
Cellular respiration terms.