Metabolism Basics

Catabolic and anabolic pathways are often coupled in a cell because

• the intermediates of a catabolic pathway are used in the anabolic pathway.

• both pathways use the same enzymes.

• the free energy released from one pathway is used to drive the other pathway.

• the activation energy of the catabolic pathway can be used in the anabolic pathway.

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According to the first law of thermodynamics,

• every energy transfer results in an increase in disorder or entropy.

• the total amount of energy in the universe is conserved or constant.

• energy can be transformed or transferred, but disorder always increases.

• potential energy is converted to kinetic energy, and kinetic energy is released as heat.

When a cell breaks down glucose only 34% of the energy is captured in ATP molecules. The remaining 66% of the energy is

• used to increase the order necessary for life to exist.

• lost as heat, in accordance with the second law of thermodynamics.

• used to increase the entropy of the system by converting kinetic energy into potential energy.

• released when the ATP molecules are hydrolyzed.

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A negative delta G means that

• the reactants have more free energy than the products.

• the reaction is spontaneous.

• the reaction is exergonic.

• all of the above are true.

The formation of ATP from ADP and inorganic phosphate

• is an exergonic reaction.

• transfers the phosphate to an intermediate that becomes more reactive.

• produces an unstable energy compound that can drive cellular work.

• involves the hydrolysis of a phosphate bond.

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In an experiment, changing the pH from 7 to 6 resulted in an increase in product formation. From this we conclude that

• the enzyme became saturated at pH 6.

• the enzyme's optimal pH is 6.

• the enzyme was in a more active shape at pH 6.

• this enzyme works best at neutral pH.

When substance A was added to an enzyme reaction, product formation deceased. The addition of more substrate did not increase product formation. From this we could conclude that substance A could be

• a cofactor.

• product molecules.

• a competitive inhibitor.

• a noncompetitive inhibitor.

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Which of the following characteristics is most directly responsible for the specificity of a protein enzyme for its substrate?

• its primary structure.

• its secondary and tertiary structures.

• the shape and characteristics of its allosteric site.

• the R groups of the amino acids in its active site.

An enzyme raises which of the following?

• the free energy of products.

• the free energy of activation.

• the speed of a reaction.

• the delta G.

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In the metabolic pathway A > B > C > D > E, what effect would molecule E likely have on the enzyme that catalyzes A > B to slow the formation of more E?

• allosteric inhibitor

• allosteric activator

• competitive inhibitor

• feedback activator

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