title: K on and K off in reverse reaction kinetics
body: <p>I am trying to code for a reverse reaction in biology - I have already done that by taking inspiration from a sample code pasted below. What I don't understand is how is the association rate constant (Kb in the code) and dissociation constant (Ku in the code) are affecting the forward and backward reactions in this code. Are they affecting the speed of movement of the products after they are formed? Are they affecting the speed with which they are formed? I want the Ku to affect affinity for substrates to form a product, and Ku to affect time to dissociate for products. The product is a complex formation of two substrates.</p>
  <p>Also, why do they multiple Kb by 2? To slow the product complex down or speed it up? It should slow down due to increase in mass.</p>
  <pre><code>breed [reactants reactant]    ;; reactants are green, products are red breed [products product]
  
  to setup   clear-all   set-default-shape reactants &quot;molecule1&quot;   set-default-shape products &quot;molecule2&quot;   create-reactants number
      [ set color green
        setxy random-xcor random-ycor ]   reset-ticks end
  
  to go   ask turtles
      [ rt random-float 10 - random-float 10  ;; wander around randomly
        fd 1 ]   ask turtles
      [ ifelse (breed = reactants)
          [ react-forward ]  ; reactants
          [ react-backward ] ; products
      ]   tick end
  
  to react-forward   if (any? other reactants-here) and
       ;; multiply Kb by 2 because 2 molecules are involved
       random-float 1000 &lt; (Kb * 2)
      [ ask one-of other reactants-here
          [ die ]
        set breed products
        set color red ] end
  
  to react-backward   if (random-float 1000) &lt; Ku
      [ set breed reactants    ;; change back to reactant
        set color green
        ;; then split into two reactants
        hatch 1 [ set heading random 360 ] ] end
  </code></pre>