Receptor Antagonism: Competitive vs Non-Competitive

Ligand Concentrations

Agonist [A] 1.0 units

Antagonist [B] 5.0 units

Antagonist Mode

Receptor Bed

Receptor count 80

Agonist-bound (active) Antagonist-bound / blocked Free receptor

Live Readouts

Agonist occupancy

0.0%

Effect (% E_max)

0.0%

Apparent EC50

1.00 units

How it works

Each receptor is modelled with simple occupancy theory. The orthosteric (agonist) site has affinity K_A = 1; a competitive antagonist fights for the same site with affinity K_B = 5, while a non-competitive antagonist binds a separate allosteric site (K_B,nc = 5) that silences the receptor without blocking agonist binding:

Competitive:
  EC50_app = K_A · (1 + [B]/K_B)
  p_A = [A] / ([A] + EC50_app)      → occupancy
  Effect = E_max · p_A               → parallel right-shift, same E_max

Non-competitive:
  p_A = [A] / ([A] + K_A)            → occupancy unaffected by [B]
  p_block = [B] / ([B] + K_B,nc)     → fraction silenced allosterically
  Effect = E_max · p_A · (1 - p_block)  → same EC50, lower E_max

[A] slider — agonist concentration on a log scale (10⁻³ to 10² relative units).
[B] slider — antagonist concentration, linear (0–20 units).
Mode buttons — switch which mechanism [B] uses to fight the agonist.
Each receptor instance carries a fixed random "identity" number; it is colored green/red/grey each frame by comparing that number against the current occupancy probabilities — so the population visibly redistributes as you move the sliders, exactly like a titration.
The curve on the right plots Effect vs log[A] at the current [B]; the dashed curve is the no-antagonist baseline, so you can see the shift (competitive) or the flattening (non-competitive) directly.

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