Chapter 4: Enzymes and Energy

Which of these represents an endergonic reaction? ADP + Pi -> ATP ATP -> ADP + Pi glucose + O2 -> CO2 + H2O CO2 + H2O -> glucose

ADP + Pi -> ATP and CO2 + H2O -> glucose

Which of these statements about ATP is true? The bond joining ADP and the third phosphate is a high-energy bond. The formation of ATP is coupled to energy-liberating reactions. The conversion of ATP to ADP and Pi provides energy for biosynthesis, cell movement, and other cellular processes that require energy. ATP is the "universal energy carrier" of cells.

All of these are true.

Which of these statements about lactate dehydrogenase is true? It is a protein. It oxidizes the lactic acid. It reduces another molecule (pyruvic acid).

All of these are true.

Which of these statements about enzymes is true? Most proteins are enzymes. Most enzymes are proteins. Enzymes are changed by the reactions they catalyze. The active sites of enzymes have little specificity for substrates.

Most enzymes are proteins.

Which of these statements about enzyme-catalyzed reactions is true? The rate of reaction is independent of temperature. The rate of all enzyme-catalyzed reactions is decreased when the pH is lowered from 7 to 2. The rate of reaction is independent of substrate concentration. Under given conditions of substrate concentration, pH, and temperature, the rate of product formation varies directly with enzyme concentration up to a maximum, at which point the rate cannot be increased further.

Under given conditions of substrate concentration, pH, and temperature, the rate of product formation varies directly with enzyme concentration up to a maximum, at which point the rate cannot be increased further.

In an inborn error of metabolism,

a genetic change results in the production of a defective enzyme; intermediates produced prior to the defective step accumulate; alternate pathways are taken by intermediates at branch points that precede the defective step

According to the law of mass action, which of these conditions will drive the reaction A + B <-> to the right?

an increase in the concentration of A and B AND a decrease in the concentration of C

Enzymes increase the rate of chemical reactions by

decreasing the activation energy of the reactants

When oxygen is combined with 2 hydrogens to make water,

oxygen is reduced AND the molecule that donated the hydrogens becomes oxidized

In a metabolic pathway,

the product of one enzyme becomes the substrate of the next