Thermodynamics - Basic 10 Flashcards
(10 cards)
What does it mean when ΔG < 0?
The reaction is spontaneous—favorable under current conditions. It will proceed without continuous energy input.
Does a spontaneous reaction happen quickly? Why or why not?
Not necessarily. ΔG relates to thermodynamics, not kinetics. A high activation energy can make spontaneous reactions slow.
What is the equation connecting ΔG and ΔG°?
ΔG = ΔG° + RTln(Q)
Why does ATP hydrolysis drive unfavorable reactions?
ATP hydrolysis releases a large amount of free energy (ΔG° ≈ –30.5 kJ/mol), which can be coupled to unfavorable reactions to make the overall ΔG negative.
What determines whether entropy makes a process spontaneous?
If ΔS > 0 and T is high, the TΔS term can make ΔG negative.
Can ΔS be negative and a reaction still be spontaneous?
Yes, if ΔH is negative and large enough to offset –TΔS.
What is the biological standard state, and why is it different from chemical standard state?
Biological standard state assumes [H⁺] = 10⁻⁷ (pH 7), whereas chemical standard is 1 M H⁺. Biochemical reactions usually occur at physiological pH.
What is Q in ΔG = ΔG° + RTln(Q)?
Q is the reaction quotient, the ratio of products to reactants at any given moment.
What does a large K (>1) tell you about ΔG°?
ΔG° is negative. The reaction favors products at equilibrium.
Why is ATP’s ΔG° of hydrolysis more negative in cells than in test tube conditions?
Due to actual cellular concentrations (far from standard state), the ΔG becomes even more negative under real biological conditions.
