DEPARTMENT OF BIOLOGY
Illustrating the Concepts Using Legos
Legomovie 1 disassembly of red/blue
To understand enzyme reactions, we need to "play a movie" in our heads. These animations are designed to help us build that movie.
In the first two, we use a hand as an analogy of the enzyme, and legos as analogies of the molecules the enzyme works upon.
Legomovie 2 assembly of red/blue
Legomovie 3 disassembly of red/blue with simultaneous assembly of yellow/green
In these next two movies, we replace the hand with something that is shaped more like an enzyme. We illustrate two kinds of processes in which the enzyme catalyzes two different reactions at once. These are "coupled reactions."
Legomovie 4 reciprocal transfer between red/blue and yellow/green
Illustrating the Concepts Without Legos This animation should provide a more accurate "mental movie," showing structures that are more like real molecules, built from atoms. Many cellular reactions require the cofactor, NAD, which extracts a hydrogen atom from the substrate. Here, we use a word as an analogy for the substrate. Use of NAD #2 Another illustration of the use of NAD, using simplified images of the compounds involved. The enzyme transfers a hydride from the substrate to NAD, as the substrate picks up an OH- from the surrounding solution. A real enzyme and a real substrate combine the concepts illustrated above, in a more realistic image. The Concept of Stored Kinetic Energy Chemical bonds hold molecules together that could otherwise move randomly. The Concept of Coupled Reactions Many enzymes catalyze two reactions at once. One releases energy, the other requires energy. This cartoon provides a way to think about how this works. How Enzymes Work
Enzymes catalyze reactions because they hold the substrate molecules in a way that makes the reaction proceed more easily. This is one way it can work.
Lysozyme is an enzyme in egg white that destroys the polysaccharides of bacterial cell walls. We know how it works. Amylase Amylase is an enzyme in saliva that breaks starch into glucose monomers. Enzymes align the chemical groups of the substrates with chemical groups on the surface of the enzyme. This triggers the movement of electrons that is the reaction. tRNA-charging Amino acyl-tRNA Synthetases carry out a two-step reaction involving ATP. Activation Energy We have an innate sense of "activation energy"--the energy needed to start a reaction. This is not the same as the overall energy gained or lost when the reaction is over.
last updated:Dec. 22, 2014