SI Session 10/03/14
*The less stable you are, the higher free energy you have!!
Chapter 8 Questions
1. Which of the following metabolic processes can occur without a net influx of energy from
some other process?
A) ADP + Pi → ATP + H2O
B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
C) 6 CO2 + 6 H2O → C6H12O6 + 6 O2
D) amino acids → protein
E) glucose + fructose → sucrose
2. According to the first law of thermodynamics,
A) matter can be neither created nor destroyed.
B) energy is conserved in all processes.
C) all processes increase the disorder of the universe.
D) systems rich in energy are intrinsically stable.
E) the universe constantly loses energy because of friction.
3. Choose the pair of terms that correctly completes this sentence:
Catabolism is to anabolism as ________ is to ________.
A) exergonic; spontaneous
B) exergonic; endergonic
C) free energy; entropy
D) work; energy
E) entropy; enthalpy
4. Living organisms increase in complexity as they grow, resulting in a decrease in the
entropy of an organism. How does this relate to the second law of thermodynamics?
A) Living organisms do not obey the second law of thermodynamics, which states that
entropy must increase with time.
B) Life obeys the second law of thermodynamics because the decrease in entropy as the
organism grows is balanced by an increase in the entropy of the universe.
C) Living organisms do not follow the laws of thermodynamics.
D) As a consequence of growing, organisms create more disorder in their environment than
the decrease in entropy associated with their growth.
E) Living organisms are able to transform energy into entropy.
Relate concept of entropy to sugar dissolving in a cup of water then reappearing later when
water evaporates.
Sugar (solid) dissolves in water to become a liquid, meaning entropy is positive, lending to
the 2nd law of thermodynamics; however, when sugar recrystallizes from liquid to solid,
entropy is negative (become more orderly), so how do we explain this? We are told that
water EVAPORATES meaning it goes from liquid to gas, adhering to 2nd law of
thermodynamics (more disorder) and the total reaction follows the law.
5. Which of the following reactions is most likely to be coupled to the reaction ATP + H2O
→ADP + Pi (ΔG = -7.3 kcal/mol)?
A) A + Pi → AP (ΔG = +10 kcal/mol)
B) B + Pi → BP (ΔG = +8 kcal/mol)
C) CP → C + Pi (ΔG = -4 kcal/mol)
D) DP → D + Pi (ΔG = -10 kcal/mol)
E) E + Pi → EP (ΔG = +5 kcal/mol)
Key thing to note: thermal energy (heat) cannot really be harnessed to do cellular work.
6. What would decrease the entropy?
A) dehydration reaction
B) respiration
C) working out in the gym
D) catabolism
E) cutting the grass
7. What is an enzyme? Is it consumed in the reaction? How does it quicken a reaction?
An enzyme is a catalyst that is a protein; it is not consumed, and it lowers the activation
energy of reactions
8. What’s the activation energy of a reaction?
Amout of energy needed to push reactants to top of an energy barrier; molecules absorb
from surroundings and it accelerates the reactants to where they collide more often and
unstable so bonds will break. Unstable condition = transition state.
9. Why is addition of heat inappropriate for biological systems?
1. high temperature denatures proteins and kills cells 2. Heat speeds up all reactions, not
just those needed
T/F Enzymes occasionally change the free energy of reactions.
10. What’s the structure called when an enzyme binds to its substrate?
Enzyme-substrate complex
11. What accounts for enzymes’ high specificities?
3D configurations; shape; amino acid sequence
12. Where does the substrate bind?
Active site
13. Can the enzyme change shapes?
Interactions between substrate chemical groups and chemical groups on side chains of the
amino acids can change the shape that makes an INDUCED FIT that is like a handshake.
14. Know the ways the active site can speed up a reaction.
1) acting as a template for substrate orientation
2) stressing the substrates and stabilizing the transition state
3) providing a favorable microenvironment
4) participating directly in the catalytic reaction
15. Discuss effects of temperature and pH on these enzymes.
16. What are cofactors? Coenzymes?
Nonprotein helpers for catalytic activity; some are inorganic (zinc, iron, and copper); if
cofactor is organic, it’s coenzyme (NAD+, vitamins)
17. Compare and contrast competitive and noncompetitive inhibitors.
Competitive mimics the substrate and blocks substrates; held by weak interactions (can be
overcome by lots of substrate)
Noncompetitive bind allosterically and changes the site of the active site (toxins, poisons,
penicillin)
18. What’s allosteric regulation?
Protein’s function at one site is affected by the binding of a regulatory molecule to a
separate site; inhibition or stiulation.
Composed of two or more subunits; oscillates between two different shapes; activator or
inhibitor binds to regulatory site to stabilize that form
19. What’s cooperativity?
One substrate molecule primes the enzyme to add additional substrate molecules more
readily
20. Discuss feedback inhibition with enzymes.
Molecules and compounds are made through complex pathways; the finalized product can
allosterically bind to the first enzyme needed to inhibit production of the first product.