How does the form of enzymes relate to their function?

Target 2.11 – Enzyme Form

In which organic class would you place enzymes?

A) CarbohydratesB) LipidsC) ProteinsD) Nucleic Acids

ENZYME FORM

• Enzymes are intricate, highly folded proteins made of thousands of amino acid monomers.

Target 2.11 – Enzyme Form

What is name of the molecule(s) with which an enzyme reacts in a chemical reaction?

A) SubstratesB) SurfactantsC) CompetitorsD) Active Sites

SUBSTRATES

• The molecule that interacts with an enzyme in a chemical reaction is the substrate.

Target 2.11 – Enzyme Form

In the equation below, which substance is the substrate?

A) Hydrogen PeroxideB) CatalaseC) WaterD) Oxygen Gas

CATALASE & H2O2

In the decomposition of hydrogen peroxide into water and oxygen gas, hydrogen peroxide is the substrate, catalase is the enzyme and water & oxygen are the products

Target 2.11 – Enzyme Form

In the diagram below, what type of reaction is being catalyzed by sucrase?

A) NeutralizationB) Dehydration SynthesisC) HydrolysisD) Homeostasis

SUCRASE

• Sucrase catalyzes the hydrolysis of the disaccharide sucrose into the monosaccharides glucose and fructose

Target 2.11 – Enzyme Function

How does an enzyme catalyze a chemical reaction with a substrate?A) By buffering the addition of H+ or OH- ionsB) By raising the temperature of the systemC) By reducing the number of substrate molecules in

the reactionD) By reducing the activation energy of the reaction

Enzymes & EA

• Enzymes reduce the activation energy (EA) necessary for a chemical reaction to proceed.

Target 2.12 – Enzyme Specificity

Where must the enzyme pair with the substrate in order for it to function properly?A) Functional GroupB) Active SiteC) Nucleation SiteD) β-Glycosidic Linkage

The Active Site

• Enzymes pair with their substrates at the active site. Other substances may compete for access to this site, preventing chemical reactions.

Target 2.12 – Enzyme Specificity

To what does the “lock & key hypothesis” refer?A) How enzymes must be unlocked by co-enzymes

before they can functionB) How competitive inhibitors lock out enzymes by

binding to the substratesC) That every enzyme reacts with two substratesD) That each enzyme can only pair with one specific

substrate

Lock and Key Hypothesis

The lock and key hypothesis describes the 1:1 specificity of enzyme to substrate. Only one substrate can match the active site of any particular enzyme

Back to the apples…

Catechol

• Substrate molecule found in the fleshy tissue of many fruits like apples, bananas, pears

Catechol Oxidase

• Enzyme that reduces the activation energy needed to oxidize catechol

Formation of Antimicrobial

• The substrate catechol combines with catechol oxidase at the active site, allowing for oxidation of catechol

• The resultant product is ortho- or benzoquinone, a natural antimicrobial

Melanin

• Ortho-quinone then reacts with oxygen gas in the presence of the enzyme tyrosinase to produce melanin

• Melanin produces the color change to brown, similar to how your body tans when exposed to sunlight.

How do you prevent the production of melanin in fruit?

WHY?

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

called DENATURATION• When an enzyme is denatured, it does not fit with

the substrate• Activation energy requirements return to their

normal level, which is often too high for the reaction to proceed at normal temperatures

• Denaturation is usually not reversible.

What Other Factors May Affect The Rate of Enzymatic Reaction

Concentration and Reaction Rate

• 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

Temperature and Reaction Rate

• Temperature is a measurement of molecular speed

• At a lower temperature, molecules collide less frequently

• At higher temperatures molecules collide more frequently

• Enzymes tend to have an optimal temperature at which they function