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Exam 8: An Introduction to Metabolism

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Question 1

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Which of the following statements regarding enzymes is true?

A) Enzymes increase the rate of a reaction by making the reaction more exergonic.
B) Enzymes increase the rate of a reaction by lowering the activation energy barrier.
C) Enzymes increase the rate of a reaction by reducing the rate of reverse reactions.
D) Enzymes change the equilibrium point of the reactions they catalyze.
E) Enzymes make the rate of a reaction independent of substrate concentrations.

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Question 2

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When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

A) It is used to power yet more cellular work.
B) It is used to store energy as more ATP.
C) It is used to generate ADP from nucleotide precursors.
D) It is lost to the environment.
E) It is transported to specific organs such as the brain.

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Question 3

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Organisms can increase their order, seemingly defying the second law of thermodynamics. This can only be accomplished if they

Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.

For the hydrolysis of ATP to ADP + ᵢ, the free energy change is -7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products) . In the cellular environment, however, the free energy change is about -13 kcal/mol. What can we conclude about the free energy change for the formation of ATP from ADP and ᵢ under cellular conditions?

Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on-off switch for a protein's activity, most likely through

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

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

The following questions are based on the reaction A + B ↔ C + D shown in the figure below. -Which of the following represents the activation energy required for a noncatalyzed reaction in the figure above?

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

Which of the following is an example of potential rather than kinetic energy?

Use the following information to answer the questions below. A patient comes into the emergency room having accidentally ingested methanol (a component in anti-freeze) . Methanol toxicity can lead to blindness, neurological issues, or death and must be treated quickly. Methanol is oxidized by the enzyme alcohol dehydrogenase (ADH) to produce formaldehyde which is then converted to formic acid. ADH has a higher affinity to ethanol, where it functions to oxidize ethanol into acetaldehyde with the end product of the pathway being acetic acid (vinegar) . -Knowing what you know about enzyme function, what would be your suggested course of treatment?

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don't often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR) . If a resting muscle cell's cytosol has a free calcium ion concentration of 10⁻⁷ while the concentration in the SR is 10⁻², then how is the ATPase acting?

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