At a given temperature, pressure, and composition, a decrease in Gibbs free energy means that a reaction can proceed in that direction without an additional energy input. The sign depends on conditions, including reactant and product concentrations. It does not tell you how quickly the reaction proceeds.
Reactants often need to pass through higher-energy arrangements before reaching products. This activation barrier can make a favorable reaction very slow. A catalyst provides another pathway with a lower barrier. It participates in the mechanism but is regenerated overall, rather than being consumed once for every product molecule.
A catalyst does not change the free energies of the same starting and ending states. It can speed the approach to equilibrium, including both forward and reverse reactions. It cannot by itself make an unfavorable equilibrium favorable. Minerals, metal ions, or RNA can act as catalysts in suitable systems; a catalyst need not be a protein enzyme.
At equilibrium, forward and reverse processes balance. Reactions do not simply cease at the molecular level, but there is no sustained net conversion in a closed system. Early evolving systems would have needed continued access to matter and usable energy rather than relying on a one-time supply forever.
Read the energy diagram as a pathway, not a clock
Locate the reactants and products before looking at either curve's peak. In this diagram the products have lower free energy than the reactants under the stated conditions. The difference between those endpoints describes the overall thermodynamic change. The peak represents an intermediate barrier along a possible reaction pathway. These are two different comparisons: endpoint against endpoint, and peak against the starting state.
The horizontal axis describes progress through molecular arrangements, not elapsed seconds. A wider drawn curve does not mean that a reaction takes longer. Nor can you calculate a rate from the height of this schematic, because the figure provides no measured energy scale or kinetic model. Its purpose is to show that two pathways can have the same starting and ending states while requiring different barriers to be crossed.
At a fixed temperature, molecules do not all have identical energies or arrangements. A reaction depends on reaching suitable configurations, not merely on the products being energetically favorable. A lower-barrier pathway can make those successful events more frequent. This explains how a reaction can have a favorable overall direction yet proceed too slowly to matter before its reactants are lost or its environment changes.
A catalyst participates in a pathway and is regenerated overall. It does not have to remain chemically unchanged at every intermediate step. However, if a supplied substance is consumed in a fixed amount for each product molecule and must be replaced, that consumption belongs in the material and energy accounting. Calling the substance a catalyst does not remove its cost or establish that it can support repeated reactions.
For the same reactants, products, and conditions, a catalyst also provides a pathway for the reverse reaction. At equilibrium, forward and reverse conversions continue at equal overall rates. Adding a catalyst does not create a new permanent imbalance between them. If an experiment changes both the catalyst and the solution's acidity or composition, a changed final product ratio cannot automatically be attributed to catalysis alone. The surrounding conditions have changed too.
Imagine comparing two closed samples started with the same reactants. At an early observation time, the catalyzed sample may contain much more product because it approached equilibrium sooner. This does not show that its equilibrium composition differs. To separate a rate effect from a final-composition effect, follow the amounts over time under matched conditions and examine whether the samples approach the same state. Product degradation or competing reactions would require additional accounting.
Return to the two curves and predict what changes when only the pathway changes. The lower peak can support faster conversion, but the endpoints remain fixed in the drawing. Now imagine changing reactant concentrations instead. That can change the overall driving force, so it is not represented merely by lowering the same peak. This distinction will help you recognize why adding a mineral catalyst, adding more feedstock, and removing product are different interventions in an origin experiment.