CH 8 Intro to Metabolism Self Quiz

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Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

Self-Quiz Questions

Choose the pair of terms that correctly completes this sentence:

Catabolism is to anabolism as ____ is to ____.

Most cells cannot harness heat to perform work because

a.	heat is not a form of energy.
b.	cells do not have much heat; they are relatively cool.
c.	temperature is usually uniform throughout a cell.
d.	heat can never be used to do work.
e.	heat denatures enzymes.

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 order of the universe.
d.	systems rich in energy are intrinsically stable.
e.	the universe constantly loses energy because of friction.

Which of the following metabolic processes can occur without a net influx of energy from some other process?

If an enzyme has been inhibited noncompetitively,

a.	the G for the reaction it catalyzes will always be negative.
b.	the active site will be occupied by the inhibitor molecule.
c.	raising substrate concentration will increase the inhibition.
d.	more energy will be necessary to initiate the reaction.
e.	the inhibitor molecule may be chemically unrelated to the substrate.

If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is to

a.	add more of the enzyme.
b.	heat the solution to 90°C.
c.	add more substrate.
d.	add an allosteric inhibitor.
e.	add a noncompetitive inhibitor.

If an enzyme is added to a solution where its substrates and products are in equilibrium, what would occur?

a.	Additional product would be formed.
b.	Additional substrate would be formed.
c.	The reaction would change from endergonic to exergonic.
d.	The free energy of the system would change.
e.	Nothing; the reaction would stay at equilibrium.

Some bacteria are metabolically active in hot springs because

a.	they are able to maintain a cooler internal temperature.
b.	high temperatures make catalysis unnecessary.
c.	their enzymes have high optimal temperatures.
d.	their enzymes are insensitive to temperature.
e.	they use molecules other than proteins as their main catalysts.

Which of the following characteristics is not associated with allosteric regulation of an enzyme's activity?

a.	A mimic of the substrate competes for the active site.
b.	A naturally occurring molecule stabilizes a catalytically active conformation.
c.	Regulatory molecules bind to a site remote from the active site.
d.	Inhibitors and activators may compete with one another.
e.	The enzyme usually has a quaternary structure.

10.

In the following branched metabolic pathway, a dotted arrow with a minus sign symbolizes inhibition of a metabolic step by an end product:

Which reaction would prevail if both Q and S were present in the cell in high concentrations?