Inhibición competitiva | Energía y enzimas | Biología | Khan Academy en Español

Enzyme Catalysis and Competitive Inhibition

Understanding Enzyme Function

• An enzyme catalyzes a reaction by binding to a substrate at its active site, facilitating the conversion of the substrate into products.

• After the reaction, the enzyme remains unchanged while the substrate is transformed into smaller molecules that are released from the active site.

Competitive Inhibition Explained

• The video introduces competitive inhibition, where an inhibitor competes with the substrate for binding to the enzyme's active site.

• A classic example involves a molecule resembling the substrate that binds to the active site first, preventing substrate access and halting catalysis.

Mechanisms of Competitive Inhibition

• The scenario illustrates how both substrate and inhibitor vie for attachment to the enzyme; if one binds first, it blocks access for the other.

• This competition can be visualized as two entities fighting for entry into a limited space (the active site).

Allosteric Competitive Inhibition

• Another form of competitive inhibition is allosteric inhibition, where an inhibitor binds to an allosteric site rather than directly competing at the active site.

• Binding at this alternative location alters enzyme conformation, making it impossible for substrates to bind effectively at their intended sites.

Implications of Allosteric Binding

• If an allosteric competitor binds first, it prevents any subsequent binding of substrates at their active sites.

• The dynamics between these competitors highlight that only one can successfully bind at any given time—either a substrate or an inhibitor.

Clarifying Misconceptions in Inhibition Types

• It’s important to note that in all forms of competitive inhibition (including allosteric), only one entity can occupy binding sites on enzymes simultaneously.

• The discussion emphasizes confusion around terminology; some may incorrectly label allosteric inhibition as non-competitive due to its mechanism not involving direct competition for the active site.

Transitioning to Non-Competitive Inhibition

• Non-competitive inhibition allows both inhibitors and substrates to bind simultaneously but inhibits reaction progression when an inhibitor is present.

• This distinction clarifies that while competitive inhibitors block access directly, non-competitive inhibitors alter functionality without blocking initial binding.