Why climb the mountain…?

“We choose to go to the moon not because it is easy, but because it is hard…because that challenge is one we are worthy to take”-John F. Kennedy 9/12/61

Why don’t these organisms bioluminesce naturally?

Bioluminescence & Changes In Potential Energy

• In order for molecules in a living organism to bioluminesce, the electrons must be accelerated to a higher energy state

• As the electrons “fall back”, the difference in energy is given off as light

• Raising molecules to this state requires more energy than most organisms can provide

What are enzymes and how do they function?

Enzyme Form

• Enzymes are complex proteins consisting of hundreds of amino acids

• Enzymes have highly specific 3D structures held together by a combination of strong bonds and weak intermolecular forces

How does the function of enzymes dictate their form?

ACTIVATION ENERGY

• All chemical reactions require ACTIVATION ENERGY to allow the reaction to proceed

• Given the symbol EA, activation energy is the minimum amount of energy needed to make a chemical reaction start.

Potential Energy Changes In Chemical Reactions

• In a chemical reaction, the amount of potential energy changes depending upon whether or not products are being synthesized or broken apart

• In either case, ACTIVATION ENERGY (EA) is required to make the reaction proceed

Endergonic v. Exergonic Reactions

• In ENDERGONIC reactions the amount of potential energy in the products is more than in the reactants

• In EXERGONIC reactions, the amount of potential energy in the products is less than in the reactants

How does the form of enzymes reduce the activation energy required for

chemical reactions?

Enzyme Specificity• Every enzyme is

specific to only one type of molecule or polymer

• This substance with which the enzyme “fits” is called a SUBSTRATE

• Since only one enzyme can match with one substrate, this fit is called the LOCK AND KEY HYPOTHESIS

ACTIVE SITES

• The substrate can fit with only one enzyme due to the specific protein shapes present at the ACTIVE SITE

• If the active site is changed/altered, in cannot fit with the substrate anymore

Competitive Inhibition and Herbicides

• Herbicides function by binding to the active sites of plant enzymes

• By blocking the enzyme from binding with their intended substrates, necessary chemical reactions cannot take place

Coenzymes

• Coenzymes are metal ions that are part of the active site

• Coenzymes assist enzymes in that their charge helps weaken the strong bonds in the substrates

• Ex: Niacin, Cobalt, Selenium, Zinc

Assisting Chemical Reactions Through Fit

• Enzymes hold the substrate in place at the active site so that other molecules can react with the substrate

• Less reliant on random collisions

Reducing Activation Energy

• Since the reaction is less dependent upon random collisions, the molecules involved need not move as fast

• Since molecules need not move as fast, less activation energy needs to be supplied at the start

At the end of a reaction, because the enzyme has not been chemically changed, it may be reused for

another reaction at another time

Example: Lactase

Factors Affecting Enzyme Function

• Because the relationship between substrate and enzyme is so specific, changing the number of enzymes reacting with the substrate (or vice versa) may affect the rate of reaction

• Ex: Vmax

DENATURATION

• One way that the rate of reaction may be reduced is by reducing the number of enzyme molecules that can fit with the substrate through altering the shape of the enzyme

• Altering the shape of an enzyme in this manner is called DENATURATION

• Enzymes may be denatured by drastic changes in heat, pH or exposure to heavy metal ions

Denaturation and Activation Energy

• Enzymes have a range of tolerance for change but outside of this range, they lose their specific 3D shape

• Since this new shape means the substrate can no longer held in place, more energy is needed to make the reaction occur

• Loss of enzyme shape = higher activation energy