Mastering Biology Chapter 8 Pre-Lecture Assignment

b. a space station orbiting Earth

b. energy cannot be created or destroyed but can be converted from one form to another

b. potential

e. cellular respiration

b. heat, carbon dioxide, and water

3 Phosphate groups attached to a Ribose attached to Adenine

e. hydrolysis

e. the products have less potential energy than the reactants

c. heat has been released to the environment

c. exergonic

e. exergonic

c. endergonic

e. ATP

e. endergonic

d. exergonic

d. It is acquired by a reactant in an endergonic reaction.

e. endergonic

a. exergonic ... uphill

a. the use of energy released from an exergonic reaction to drive an endergonic reaction

a. proteins

c. reducing EA

b. is an organic catalyst

b. substrate

e. is unchanged

a. energy of activation

Most product formed ---> Least product formed reaction catalyzed by enzyme B--->reaction catalyzed by enzyme A--->uncatalyzed reaction Enzymes lower the activation energy of a chemical reaction. This means that a catalyzed reaction is more likely to proceed than an uncatalyzed reaction, and it forms products more rapidly than an uncatalyzed reaction.

Hint: A substrate binds at an enzyme's active site; the enzyme typically recognizes the specific shape of its substrate. A cofactor, such as an inorganic ion or vitamin, may bind to the enzyme and assist in catalyzing the reaction. The reaction environment must be appropriate for catalysis to proceed. An enzyme will denature, or change its shape and lose its biological activity, at too high a temperature or at a pH outside the enzyme's optimal range.

c. region C (In region C of the graph, the reaction rate is independent of substrate concentration.)

c. region C

c. Increase the enzyme concentration. If an enzyme is saturated with substrate, and it is operating at optimum pH and optimum temperature, there is very little that can be done except to increase the enzyme concentration. Some enzymes can be activated further by allosteric activators, in which case one might add some activator to the reaction. But otherwise, increasing the enzyme concentration is the only option.

1. competitive 2. noncompetitive 3. irreversible 4. active site 5. enzyme 6. substrate Competitive inhibitors compete physically and structurally with the substrate for an enzyme's active site; they can be outcompeted by adding extra substrate. Noncompetitive inhibitors do not compete for the active site, but inhibit the enzyme by binding elsewhere and changing the enzyme's shape. Irreversible inhibitors bind directly to the active site by covalent bonds, which change the structure of the enzyme and inactivate it permanently. Most medications are enzyme inhibitors of one kind or another.

b. The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. Because they bind directly to the active site by covalent bonds, irreversible inhibitors permanently render an enzyme inactive. Some drugs are irreversible inhibitors, including the antibiotic penicillin (which inhibits an enzyme involved in bacterial cell-wall synthesis) and aspirin (which inhibits cyclooxygenase-2, the enzyme involved in the inflammatory reaction).

b. Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Competitive inhibition can be overcome by adding more substrate to outcompete the inhibitor. Many drugs used to treat different medical conditions, including hypertension, are competitive inhibitors. It is fairly easy to make a molecule that is similar in structure to a particular substrate because the known enzyme's shape can be used as a model of what the molecule needs to look like. It is more difficult to make a noncompetitive inhibitor because it is less obvious what the noncompetitive inhibitor's shape and structure should be.

c. P4 binds E1 and deactivates it. Many enzymatic pathways are regulated by the feedback inhibition model described here. In fact, it is so common that another name for it is end-product inhibition.