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Enzymes. Nature’s Efficiency Experts . What are Enzymes?. Enzymes are a special group of PROTEINS Remember proteins are responsible for structure and function They are referred to as CHEMICAL CATALYSTS because they control chemical reactions without becoming a part of them.

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Nature’s Efficiency Experts

what are enzymes
What are Enzymes?
  • Enzymes are a special group of PROTEINS

Remember proteins are responsible

for structure and function

  • They are referred to as CHEMICAL CATALYSTS because they control chemical reactions without becoming a part of them.
  • The enzyme itself is not changed in the REACTION and it can be used

again and again.

examples of enzymes
Examples of Enzymes
  • Most enzymes names end with –ase.
  • Usually they are named for

the material they are acting


    • Lactose is digested by lactase
    • Sucroseis digested by sucrase
    • Cellulose is digested by cellulase

and so on…

  • What exactly does “digestion”

mean? To break bonds

between monomers in a large

polymer by enzyme activity!

enzyme control
Enzyme Control
  • There are over 4000 biochemical reactions that are controlled by enzymes…
    • Digestion: Amylase digests carbohydrates into monosaccharides. Amylase is in saliva. There are 7 digestive enzymes.
    • Toxic Byproducts: Biochemical reactions often produce substances that can be toxic to cells. Enzymes digest them into substances that are not. The enzyme catalase digests hydrogen peroxide(H2O2) into H2O and O2.
    • Poisons: Act as enzyme inhibitors, and prevent the enzyme from working. Examples can be found in Raid(animals) and Round-Up(plants). They kill certain kinds of organisms without harming others because they act on enzymes that are specific to them. Many animal toxins like snake venom do the same thing.
    • Products Detergents(oxy-), Meat tenderizers(think about it!)
how enzymes work
How enzymes work
  • Enzymes are chemically and structurally

matched to the biomolecule

they digest…

In much the same way that

a key fits a lock, in fact this

“lock and key” analogy

is often used to describe

enzyme activity.

Let’s see why…

lock and key model
“Lock and Key” Model
  • It is important to note that this reaction can run in the opposite direction…to build polymers. However, a different enzyme is used and are called polymerases.




Lock and Key

Once bond is broken

products are released

enzyme continues to

work as long as

substrate is present

Enzyme changes

Shape and by heat

and friction the

bond is broken



why are enzymes so important
Why are enzymes so important?
  • Because Nature Loves Efficiency!
    • In order for all of the activities of life to occur; all the chemical reactions, building and breaking down of materials, repair and maintenance of structures…If cells had to wait around for these materials and reactions to occur spontaneously…life would not be possible!
    • Also, needless to say all of those activities require a great deal of energy to get started, or keep going, or stop!…so much so that those little mitochondria would not be able to produce enough ATP fast enough to fuel everything a cell has to do…again life would not be possible!
  • So enzymes get the job done without the cell having to expend the energy to do it! In other words they lower the activation energy of chemical reactions so they go faster and result in more product!!!!
how can we visualize an enzyme reaction
How can we visualize an enzyme reaction?
  • NO Enzyme:
    • High activation energy
    • Longer time
    • Less Product
  • With Enzyme:
    • Less activation energy
    • Less Time
    • More Product


enzyme activity can be altered
Enzyme Activity can be altered …
  • Enzymes are very sensitive to their environment; any change can result in an enzyme that will not work effectively, or, not at all…at that point the enzyme is said to be denatured.
    • Temperature: any increase or decrease in the temperature at which the enzyme functions changes the shape of the activation site, just like when heating wax causes it to fold. If the activation site changes shape then the “key” no longer fits the “lock” and the reaction stops. This is why food doesn’t ‘digest’ well when you have a fever, and …..well,

you better be close to a toilet!

    • pH Changes: any increase or decrease in pH can denature an enzyme. Stomach enzymes are designed to work best at low pH’s(high acid), so when you have an invasion of nasty food borne bacteria, their metabolism neutralizes your stomach pH, your enzymes denature, and, again…you better be close to a toilet!

Concentration of Substrate: What happens if I eat a huge pizza? You might think lots more enzyme will be produced to take care of this “extra large” digestion issue…and you’d be right, to a point. Enzyme reaction rate depends upon open activation sites; so once they are all in use, digestion can actually slow and reach a plateau(this is why the graph doesn’t keep going up!) So, eating a lot all at once can actually slow digestion down…so, mom is right, slow down and chew your food smaller pieces means enzymes don’t have to work as hard!

  • Mutation: Since enzymes are proteins; their manufacture depends upon a correct amino acid sequence, and since that is determined by DNA, mutation can change the “nature” of the protein. Lactose intolerance is caused by a mutation. Folks with this mutation produce ineffective lactase, i.e. the shape of the “lock” is changed so they cannot properly digest milk sugar lactose. If they eat dairy, the sugar is fermented by intestinal bacteria doing their anaerobic thing and, oh gosh!

Where’s the bathroom!

= lactase in a box!