1. Chapter 4: Energy Clicker Questions
by Kristen Curran, University of Wisconsin, Whitewater 1

2. Which answer is an example of potential energy?
Heat from a fire
Sledding down a hill
A candy bar
Walking to your car
Answer: 3 2

3. In which process would you expect that the conversion of a form of potential energy into heat might be useful?
The mitochondria produce heat during cellular respiration which maintains body temperature.
In the winter, some of the heat produced by combustion can be used to maintain the temperature in the passenger compartment of your car.
The increased cellular respiration when exercising creates heat and you begin to sweat.
1 and 2
All of the above 4 3

4. Which letter in the diagram below is an example of potential energy?
A and C
B and D A D B
Answer: 5
This question can begin a discussion of high and low potential energy as well as that both the formation and breakdown of bonds is kinetic energy. C 4

5. When a plant in a pot gains weight, which input into the photosynthesis pathway added to the weight of the plant?
Carbon harvested from carbon dioxide
Oxygen harvested from carbon dioxide
Hydrogen harvested from water
Oxygen harvested from water
Answer: 1 5

6. Which wavelength of light would you expect is NOT absorbed by chlorophyll a or b?
Red
Yellow
Blue
Green
Purple 4 6

7. What do chlorophyll and fireworks have in common?
Classroom Catalyst
What do chlorophyll and fireworks have in common?
Fireworks are made up of various metal salts that go through oxidation and reduction reactions, producing great heat that causes electrons to move from their usual level around the nucleus (ground state) up to a higher position further away from the nucleus (excited state). The energy from heat has been imparted to the electron(s), which now has more potential energy. These excited electrons move almost instantaneously back down to their ground state, releasing their stored potential energy in the form of light. The greater the electrons movement away from the nucleus to the excited state, the more potential energy it has and the more energy it will release.
It should be pointed out that chlorophyll absorbs light energy, specifically its electrons, and this energy is used to pump protons instead of producing light. This proton gradient in turn is used to produce ATP, which along with other energized electrons are transferred to the Calvin cycle.
(For more information, see Activity Four of the Chapter 4 Instructor’s Manual, found on the Instructor’s Resource DVD or Faculty Lounge.)

8. What do chlorophyll and fireworks have in common?
You have seen that chlorophyll is made up of pigments that absorb light energy at specific wavelengths. How is the absorption of energy by the electron in the pigment and the firework the same? Are they different?
If harnessed in a different way, could the energy possessed by the excited electrons in the fireworks be used by plants to make food?
What are the energy sources for each?
As you answer the following questions, refer to Chapter 4, sections 4-7 through 4-10
You have seen that chlorophyll is made up of pigments that absorb light energy at specific wavelengths. How is the absorption of energy the by the electron in the pigment and the firework the same? Are they different?
Answer: Energy, in the same form, is energy. The quantity and form can vary. The energy source is different, and the amount of energy required to move an electron from ground state to an excited state is going to be different depending on what atom the electron is in.
If harnessed in a different way, could the energy possessed by the excited electrons in the fireworks be used by plants to make food?
Answer: Yes, but obviously major modifications would have to be made. But the energy, if at the same wavelength, is the same and therefore can be harnessed to do work.
What are the energy sources for each?
Answer: Plant pigment—light; firework—heat
(For more information, see Activity Four of the Chapter 4 Instructor’s Manual, found on the Instructor’s Resource DVD or Faculty Lounge.)

9. Follow up question: In the cell, excited chlorophyll a molecules:
return to the normal state after releasing the energy in the form of light.
return to the normal state after passing on electrons to another molecule.
return to the normal state after releasing the energy to directly form ATP.
remain in the normal state after passing on the energy to chlorophyll b
Answer: 2 9

10. Review: Which answer is an example of a molecule with high potential energy?
NADPH
NADP+
H2O O2
Both 1 and 2
Answer: 1
Both 1 and 2 are technically potential energy. 2 would be low potential energy. 10

11. Why does NADPH have a high potential energy?
Because it is used for electron transport
Because it is equivalent to ATP
Because it stores energy that is used to make G3P
Because it contains phosphate that can be put on ADP to form ATP
Answer: 3 11

12. What is the cost associated with a plant using C4 or CAM photosynthesis?
More energy is used to form sugars.
More CO2 is required to form sugars.
The harvest of light energy and carbon fixation are temporally separated.
Less water is lost in hot, dry climates.
Answer: 1 12

13. Review: The energy used by plants and animals ultimately comes from…
food
soil
sun
air
Answer: 3 13

14. If glycolysis is very inefficient, why do it?
Because pyruvate can be metabolized to yield more water
Because pyruvate can be metabolized to yield more CO2
Because pyruvate can be metabolized to absorb more electrons
Because pyruvate can be further metabolized to yield more energy
Answer: 4 14

15. Energy is obtained from a molecule of glucose in a stepwise fashion
Energy is obtained from a molecule of glucose in a stepwise fashion. Why would this method of harvesting energy be beneficial to the cell/organism?
It is more efficient to form sugars a little bit at a time rather than all at once.
It is more efficient to release energy a little bit at a time rather than in one giant explosion.
It is more efficient to make ATP from ADP than to make it from scratch.
All of the above.
Answer: 2 15

16. Plants have both chloroplasts and mitochondria. Why?
The mitochondria also synthesize sugars.
The mitochondria are used to convert oxygen to carbon dioxide for the plant.
The mitochondria break down sugars produced by photosynthesis to provide energy for the cellular work of the plant.
The mitochondria break down fat produced by photosynthesis to provide energy for the cellular work of the plant.
Answer: 3 16

17. Which process below uses anaerobic respiration?
Running 10 miles
Swimming 1 mile
Sprinting 100 meters
Making beer
3 and 4
Answer: 5 17