In an osmotic system with unequal solute concentrations separated by a semipermeable membrane, which thermodynamic parameter primarily governs the direction of solvent flow?

• Enthalpy difference

• Osmotic pressure difference

• Gibbs free energy difference

• Entropy difference

Which of the following best explains why osmotic pressure is a more sensitive method to determine high molecular weight compounds than boiling point elevation?

• It depends on pressure difference across a membrane

• It is independent of temperature

• It detects very small solute concentrations

• It uses a frictionless piston system

Which of the following thermodynamic changes will always ensure a spontaneous reaction under standard biological conditions?

• ΔH > 0 and ΔS < 0

• ΔH < 0 and ΔS < 0

• ΔH < 0 and ΔS > 0

• ΔH > 0 and ΔS > 0

Consider a reaction where ΔG is negative but ΔG° is positive. What must be true about the system?

• The reaction is endergonic and at equilibrium

• The actual [products]/[reactants] ratio is less than Keq

• The actual [products]/[reactants] ratio is greater than Keq

• The temperature is lower than standard

In an electrochemical cell, which of the following changes will lead to a spontaneous reaction?

• Ecell = 0

• ΔG = 0

• ΔG < 0 and Ecell > 0

• nFE = 0

Which step in glycolysis is considered metabolically irreversible and commits glucose to the glycolytic pathway?

• Hexokinase-catalyzed phosphorylation of glucose

• Isomerization of glucose-6-phosphate

• Aldolase cleavage of fructose-1,6-bisphosphate

• Triose phosphate isomerization

What is the functional rationale behind the isomerization of glucose-6-phosphate to fructose-6-phosphate in glycolysis?

• To trap glucose inside the cell

• To increase the energy yield of glycolysis

• To create a symmetric molecule for aldol cleavage

• To prepare for substrate-level phosphorylation

Phosphofructokinase-1 (PFK-1) catalyzes a major regulatory step in glycolysis. Which of the following best explains why PFK-1 is an effective metabolic control point?

• It is inhibited by glucose-6-phosphate

• It catalyzes a reversible reaction near equilibrium

• It catalyzes a highly exergonic and allosterically regulated step

• It requires FAD as a coenzyme

The aldolase step in glycolysis yields dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). Which of the following is TRUE about this reaction?

• Both DHAP and G3P directly proceed to the next glycolytic step.

• Aldolase catalyzes an irreversible aldol cleavage.

• DHAP is converted to G3P because only G3P continues in glycolysis.

• This step generates ATP via substrate-level phosphorylation.

Why is triose phosphate isomerase considered a "catalytically perfect" enzyme?

• It catalyzes a thermodynamically irreversible reaction.

• Its reaction reaches equilibrium in milliseconds.

• It proceeds at a rate limited only by substrate diffusion.

• It consumes ATP to accelerate the reaction.