Metabolism
Class Work
1. Define metabolism.
2. Define catabolic pathway.
3. Define anabolic pathway.
4. Give an example of a living system and its surroundings.
5. State the first law of thermodynamics.
6. Give an example of an endothermic system.
7. Give an example of an exothermic system.
8. Define entropy.
9. True of False: Spontaneous reactions occur quickly but only in one direction.
Explain
Homework
10. What role do enzymes play in metabolic pathways?
11. True of False: The energy of the Universe is not constant. Explain.
12. Give an example of a nonliving system and its surroundings.
13. Define endothermic.
14. Define exothermic.
15. As entropy decreases in an organism, what happens to the entropy of the
Universe?
16. State the second law of thermodynamics.
17. What is a spontaneous reaction?
Class Work
18. Do endergonic reactions have a positive or negative ∆G?
19. Which type of reaction occurs spontaneously? Exergonic or endergonic.
20. Does a spontaneous reaction increase or decrease the entropy of the
universe?
21. What is the ∆G of a reaction that occurs spontaneously?
22. What is the ∆G of a reaction that does not occur spontaneously?
Homework
22. Describe how Gibbs Free Energy and the spontaneity of reactions are related.
23. Do exergonic reactions have a positive or negative ∆G?
24. Which type of reaction does not occur spontaneously? Exergonic or
endergonic.
25. Which type of reaction releases energy? Exergonic or endergonic.
26. In which kind of reaction do the products have more free energy than the
reactants? Exergonic or endergonic.
Class Work
27. How are biological systems able to get endergonic reactions to occur?
28. What is the ∆G of a coupled reaction?
29. Name one type of energy used in living organisms?
30. How many phosphate groups are in one molecule of ATP?
31. When ATP is changed to ADP, is Gibbs Free Energy raised or lowered?
32. What type of endergonic reactions does ATP power?
Homework
33. Do endergonic processes always directly follow exergonic processes?
34. What are the three types of work done by cells?
35. When changing from AMP to ADP to ATP is energy consumed or released?
Explain why.
36. What process is used to break the bond between the second and third
phosphate group?
37. True or False: Life is not in equilibrium. Explain.
Free Response
1. The constant flow and exchange of materials is one of the driving forces that
allow life to proceed.
a. Explain how the terms enthalpy, endothermic, and exothermic are
related.
b. Give an example of an exothermic system.
2. Gibbs free energy is a defining factor in whether or not a reaction will occur
spontaneously.
a. Explain the relationship between ∆G and the spontaneity of a reaction.
b. Explain why living organisms need to couple reactions.
3. ATP is the currency of energy in living things.
a. Explain the process of formation of ATP from ADP.
b. Explain how ATP is used to provide energy for other reactions in the
cell.
Metabolism- Answer Key
1. All the chemical reactions that
happen in living organisms to
maintain life.
2. Break down complex
molecules into simpler ones by
releasing energy
3. Build complex molecules from
simpler ones while consuming
energy
4. Multiple answers acceptable.
Ex. System: plant
Surroundings: dirt, air, sun
5. Energy is neither created nor
destroyed.
6. A turkey in the oven
7. A cup of hot coffee sitting on a
table.
8. Measure of disorder
9. False: Spontaneous does not
mean quickly, but means
without outside intervention.
Spontaneous reactions do only
occur in one direction though
because in the other direction
the reaction is not
spontaneous.
10. Enzymes catalyze the
individual reactions in a
metabolic pathway
11. False: The energy of the
universe is constant; this is the
first law of thermodynamics.
12. System: a tea kettle
Surroundings: stove, air,
kitchen
13. Heat is absorbed by the system
14. Heat is released by the system
15. The entropy of the universe
increases; the second law of
thermodynamics
16. The entropy of the universe is
continually increasing
17. A reaction that occurs without
outside forces
18. Positive
19. Exergonic
20. Increase
21. ∆G is negative
22. ∆G is zero or positive
23. When Gibbs free energy is a
negative value, then the
reaction is spontaneous. When
Gibbs free energy is zero or
positive, then the reaction does
not occur spontaneously.
24. Endergonic
25. Exergonic
26. Endergonic
27. By coupling spontaneous
exergonic reactions with
endergonic reactions so that
the total Gibbs Free Energy
between the two reactions still
has a negative value.
28. A negative value
29. ATP
30. Three
31. Lowered
32. Phosphorylation reactions
33. No, the energy from exergonic
processes can be stored to
power endergonic reactions at
a later time.
34. Mechanical, transport,
chemical
35. Energy is consumed because it
takes work to overcome the
repulsion of the negative
charges on each phosphate
group in order to add another
phosphate group.
36. Hydrolysis
37. True: Life is not in equilibrium.
Life requires a constant flow
and exchange with the
environment making it an open
system.
Free Response Answers
1.
a. Enthalpy is the measure of heat in a system. When heat is
absorbed by the system, or the enthalpy increases, the process is
endothermic. When heat is lost by the system, or the enthalpy
decreases, the process is exothermic.
b. Multiple answers are acceptable: Mug of hot chocolate placed on
the table.
2.
a. If Gibbs free energy or ∆G is negative for a particular reaction, then
the reaction will occur spontaneously. If ∆G is positive or zero,
then the reaction will not occur spontaneously.
b. Living organisms have specific endergonic reactions that they
need to perform. Since these endergonic reactions do not occur
spontaneously, the endergonic reaction will couple with a
exergonic reaction therefore using the energy released from the
exergonic reaction to power the endergonic reaction. In these
coupled reactions the total ∆G is negative indicating that the
coupled reactions occur spontaneously or without the input of
other outside energy.
3.
a. ADP is a molecule that has only two phosphates; in order to form
ATP, which has three phosphates, energy is put into the reaction.
Energy is needed to overcome the electrostatic repulsion provided
by the negative charge that each phosphate group carries. ADP
undergoes phosphorylation to form ATP.
b. When ATP is hydrolyzed to form ADP and a phosphate, energy is
released. This energy can then be used to power endergonic
reactions in the cell.