GRE子ject Test: Biochemistry, Cell, and Molecular Biology : Chemical Principles

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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Example Questions

Example Question #1 :Biochemistry

Which of the following statements is not true regarding Gibbs free energy,?

Possible Answers:

If theof a reaction is zero, the reaction is at equilibrium

Theof a reaction is partially dependent on the temperature of the system

Theof a reaction is partially dependent on enthalpy of the system

If theof a reaction is less than zero, the reaction is endergonic

If theof a reaction is positive, the reaction is not favorable and likely requires external energy to proceed

Correct answer:

If theof a reaction is less than zero, the reaction is endergonic

Explanation:

If the小于零的反应,这个反应in fact be exergonic. These reactions will be favorable and spontaneous, and energy isreleasedin these reactions. Thus, endergonic is incorrect.

Example Question #2 :Biochemistry

The equilibrium constantof any given chemical reaction is__________on the temperature and pressure of the reactants and products and is__________of the reaction rate.

Possible Answers:

Independent . . . one-half

dependent . . . one-half

dependent . . . independent

dependent . . . dependent

independent . . . dependent

Correct answer:

dependent . . . independent

Explanation:

The temperature and pressure of the reactants and products of any given reaction will determine the value of. However, this is entirely dependent of the reaction rate, which is determined by how the concentrations of the reactants and products change over the course of the reaction. Additionally, every reaction is unique, so "one-half" or any other exact metric cannot be applied as the definition.

Example Question #3 :Biochemistry

Which of the following best describes a reaction that has reached equilibrium?

Possible Answers:

is less than zero, and the forward and reverse reactions are occurring at equal rates.

is greater than zero, and the forward and reverse reactions are occurring at equal rates.

is zero, and both the forward and reverse reactions have stopped occurring completely.

is zero, and the forward reaction is occurring spontaneously.

is zero, and the forward and reverse reactions are occurring at equal rates.

Correct answer:

is zero, and the forward and reverse reactions are occurring at equal rates.

Explanation:

In equilibrium, both the forward and reverse reactions continue to occur, but they do so in a way that is equal and thus, there is no net change of reactants and products in the system.is zero in this case because net changes to the system have ceased, and thus the free energy is no longer in flux.

Example Question #4 :Biochemistry

__________reactions have athat is less than zero, and thus they occur spontaneously. This is because the products in these reactions have lower bond energies than the reactants, and when that energy is released it is converted to__________.

Possible Answers:

exothermic . . . light

endothermic . . . heat

endothermic . . . light

exothermic . . . heat

exothermic . . . electricity

Correct answer:

exothermic . . . heat

Explanation:

Exothermic reactions release heat (thinkexothermic =explosion = creates heat), and this is due to the release of energy from the reactant bonds. These reactions haveless than zero. Endothermic reactions are just the opposite and actually require energy to occur, and therefore do not occur spontaneously nor release heat.

Example Question #1 :Biochemistry

Which three elements are capable of participating in hydrogen bonding?

Possible Answers:

Fluorine, oxygen, nitrogen

Francium, osmium, nobelium

Iron (Fe), oxygen, sodium (Na)

Francium, oxygen, nickel

Fluorine, osmium, nitrogen

Correct answer:

Fluorine, oxygen, nitrogen

Explanation:

A hydrogen bond is the weak attraction of a covalently bonded hydrogen to nearby fluorine, oxygen, or nitrogen (FON) atoms. These attractions can occur within a single molecule (intramolecular) or between two distinct molecules in close proximity (intermolecular). Hydrogen bonds give water its cohesiveness and its surface tension.

Example Question #6 :Biochemistry

The strength of bonds and intermolecular forces, from strong to weak, can be recalled by the use of the mnemonic "I Can't Handle Dirty Vans," which stands for__________.

Possible Answers:

ionic, covalent, hydrogen, dipole, van der Waals

isotonic, compound, homologous, dense, valance

incomplete, carbon, hardy, direct, van't Hoff

intermediate, central, hybrid, diatomic, variable

indirect, chorion, high-energy, DeVries, vital

Correct answer:

ionic, covalent, hydrogen, dipole, van der Waals

Explanation:

Ionic bonds form when one or more electrons from an atom are removed and attached to another atom resulting in positive and negative ions that attract each other. Sodium chloride is an example of an ionic compound. Covalent bonds form when one or more pairs of electrons are shared by two atoms. Hydrochloric acid is an example of a covalent compound. A hydrogen bond is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity (oxygen, nitrogen, or fluorine) in another molecule. Water molecules are capable of intermolecular hydrogen bonds. A dipole-dipole bond is an attractive force between the positive end of one polar molecule and the negative end of another polar molecule. Iodine monochloride molecules show dipole-dipole attraction. Van der Waals forces arise from spontaneous changes in electron density; these occur in all chemical molecules regardless of composition and are extremely weak interactions.

Example Question #1 :Chemical Principles

A mnemonic for remembering whether energy is required or released when chemical bonds are formed is__________.

Possible Answers:

PASS

SCAN

BARF

LEO says GER

RICE

Correct answer:

BARF

Explanation:

Energy is absorbed when bonds break. The energy required to break the bond is absorbed from the surroundings. You have to put energy into a molecule to break its chemical bond.

Energy is released when bonds form. Bond formation represents a stable configuration of atoms. If breaking a bond absorbs energy, forming a bond must release energy; thus, the mnemonic BARF—Break (a bond), Absorb (energy), Release (energy), Form (a bond).

SCAN is the mnemonic for the magnetic field induced in a coil—south clockwise, anticlockwise north. PASS stands for pull, aim, squeeze, sweep—how to use a fire extinguisher. RICE is the treatment for an injury to a joint: rest, ice, compression, elevation. LEO says GER is a mnemonic for loss of electrons is oxidation, gain of electrons is reduction.

Example Question #8 :Biochemistry

Which of the following forces is strongest between molecules of hydrochloric acid (HCl)?

Possible Answers:

Dipole-dipole interactions

London dispersion forces

Hydrogen bonding

Ionic bonding

Correct answer:

Dipole-dipole interactions

Explanation:

Since hydrochloric acid has a partial positive charge on the hydrogen and a partial negative charge on the chlorine, the molecules will have dipole-dipole interactions between them. Although hydrogen bonding is a stronger force, a hydrogen must be attached to a nitrogen, oxygen, or fluorine in order to exhibit hydrogen bonding.

Example Question #9 :Biochemistry

Which of the following molecules is not capable of hydrogen bonding?

Possible Answers:

Ethanol

Acetic acid

Correct answer:

Explanation:

Hydrogen bonding is possible when a hydrogen atom is attached to a nitrogen, oxygen, or fluorine. Of the following options, hydrochloric acidis the only option that does not fit the criteria.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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