Download In-Class Student Activity: Fate of carbon atoms during Cellular

In-Class Student Activity:
Fate of carbon atoms during Cellular Respiration: This activity helps
students visualize the fate of the carbon atoms in a glucose molecule as it is oxidized
during cellular respiration. In addition, this activity is designed so students will
distinguish between substrate level phosphorylation and oxidative phosphorylation and
understand which stage of cellular respiration makes the majority of the ATP. It
encourages student collaboration and leads to discussion that will enable the instructor
to address any student misconceptions.
Student Learning Objectives: (PSLO #1 and Course SLO#4)
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Understand the flow of energy during cellular respiration.
Understand the role of NAD+, H+ ions and Electron Transport Chain in the
process of cellular respiration.
Estimated class time:
15 to 20 minutes.
Materials Required:
1. Large poster paper, markers, apples, knives. Can also use pictures of apples,
using scissors to “cut” apples.
Note: Activity can be set up as a “race” between the two groups (as outlined below) or
done with just one large group.
Procedure:
1. Divide the class into two groups, A & B. Subdivide each larger group into four
groups of 2-3 students (A1-A4 & B1-B4).Each sub-group will represent one of the
four stages of cellular respiration:
Subgroup 1: Glycolysis
Subgroup 2: Pyruvate Oxidation
Subgroup 3: Krebs Cycle
Subgroup 4: ETC
2. Give each subgroup a large poster paper.
3. Have each group discuss and write on their poster:
a. The stage of cellular respiration assigned to their group
b. Inputs and outputs of their reaction
(For example A1 & B1. Input: 1 molecule of glucose. Output: 2 molecules
of pyruvate, 2 molecules of ATP.
4. Give groups A1 and B1 an apple and a knife. Have the group model the fate of
the carbons at the end of their stage by cutting the apple (representative of 6
carbons) with a knife.
a. For example, A1 & B1 groups will split the apple in two equal halves
(representative of two pyruvate molecules at the end of glycolysis).
5.
6.
b. The students will then need to pass (throw!) the apple pieces to the next
stage of the cycle where the A2 & B2 students will model pyruvate
oxidation (let them have fun by throwing a third of each half apple into the
air to represent release of CO2!).
By the time the A3 and B3 students have finished, the glucose is completely
oxidized (and apple pieces will be in all corners of your classroom!) and these
groups will have nothing to “pass on” to the A4 and B4 groups, yet only a small
fraction of the ATP molecules that cellular respiration can release from a glucose
molecule undergoing aerobic respiration has been generated.
Have the “A” student groups and “B” student groups get together and discuss
why this.
a. They should understand that at the end of the citric acid cycle, most of the
energy of the glucose molecules has been transferred to NADH/FADH2
and this is what will be “passed on” to the oxidative phosphorylation step.
Students can revisit their poster sheets and add where the NADH/FADH2
have been produced.
b. This is also a good place to introduce the concept of “substrate level
phosphorylation” versus “oxidative phosphorylation”.