Chapter 8 Directed Reading
1. Metabolism is the totality of an organisms chemical reactions.
2. a. catabolic
b. anabolic
c. anabolic
d. catabolic
e. anabolic
f. anabolic
g. catabolic
h. anabolic
3. Kinetic energy is energy associated with the relative motion of object. Potential energy is
energy that matter possessed because of its location or structure.
4. The water behind a dam has potential energy. A mole of glucose has chemical energy.
5. Free energy is the portion of a systems energy that can perform work when temperature and
pressure are uniform throughout the system. Its symbol is delta G.
11. A. The bond will break by the process of hydrolysis.
B. Adenosine triphosphate (ATP) contains the sugar ribose, with the nitrogenous base adenine
and a chain of three phosphate groups bonded to it.
12. 1. Negative 2. -7.3 kcal/mol (-30.5 kJ/mol)
3. Exergonic
13. A. Energy coupling is the use of an exergonic process to drive an endergonic one.
B. phosphorylated
14. You would use up nearly your entire body weight in ATP every day.
15. A catalyst is a chemical agent that speeds up a reaction without being consumed by the
reaction.
16. The activation energy is the initial investment of energy for starting a reaction, the energy
required to contort the reactant molecules so the bonds can break
a) The activation with the enzyme is lower
c) Delta G is unaffected by enzyme
17. 1. Substrates enter active site; enzyme changes shape such that its active sit enfolds the
substrates (induced fit)
2. Substrates are held in active sit by weak interactions, such as the hydrogen bonds and ionic
bonds
3. Substrates are converted to products
4. Products are released
5. Active sit is available for 2 new substrate molecules
18. Induced fit brings chemical groups of the active sit into positions that enhance their ability to
catalyze the chemical reaction. Induced fit is in step of the previous figure.
20. Active site can lower activation energy and speed up a reaction by
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
21. a. initial concentrate of substrate: The higher the substrate concentration the more quickly
product is produced (rate of reaction increases) until enzyme saturation is reached at which time
more substrate has no further effect
b. ph: Enzymes have an optimal level at which they work the best, and anything above or below
that level, their activity begins to slow down until they shut down all together, which is referred
to as denaturing the enzyme.
c. temperature: Drastic changes from optimal temperature agitate the bonds that create an
enzyme and that bind it to the substrate.
22. Raising the temperature will denature an enzyme so that it is no longer functional. Lowering
the temperature will reduce the rate of the reaction so low as to make it seem non-functional.
Altering the pH above or below its optimum pH will also reduce the enzyme’s activity.
23. A human enzyme that functions well in ph 2 is pepsin, and it is found in the stomach.
24. A cofactor is a nonprotein helper for catalytic activity. The cofactors of some enzymes are
inorganic, such as the metal atoms zinc, iron, and copper in ionic form. A coenzyme is a cofactor
that is an organic molecule. Most vitamins act as coenzymes.
25. Competitive inhibitors reduce the productivity of enzymes by blocking substrates from
entering active sites. In contrast, noncompetitive inhibitors do not directly compete with the
substrate to bund to the enzyme at the active site.
26. Allosteric regulation: a case in which proteins’ function at one site is affected by the binding
of a regulatory molecule to separate site.
27. Both change an enzyme’s shape and the functioning of its active site by binding to a site
elsewhere on the molecule, via noncovalent interactions.
28. Allosteric activation stabilizes the shape that has functional active sites while inhibitors
stabilize the inactive form of an enzyme binding.
29. The gills of a fish is an area of high oxygen concentration therefore hemoglobin will have a
greater affinity for oxygen as more binding sites are filled.