Section 2.5

Key Concept:

Enzymes lower the activation energy for chemical reactions in living things

What Are Enzymes?What Are Enzymes?

• Enzymes are a special group of protein molecules which speed up chemical rxns in living cells by lowering the activation energy (EA)

Fun Facts about EnzymesFun Facts about Enzymes

• Make rxns go 10 trillion times faster –

1500 yrs vs. 5 seconds

• Are not living

• Are reusable

• There are about 2000 different enzymes in each one of your cells

• Names usually end in -ase

How do enzymes work?

• Each enzyme has a unique 3-D shape, including a surface groove called an ACTIVE SITE.

• One or more molecules called SUBSTRATES chemically bond to the enzyme’s active site.

• When joined they are called an ENZYME-SUBSTRATE COMPLEX

• Changes in how the atoms are bonded occur resulting in new molecules being made called PRODUCTS .

• Products are then released from the active site.

How enzymes make rxns go How enzymes make rxns go fasterfaster

Enzymes work by reducing the amount of energy needed (EA) for the bonds in the substrate molecules to break

Enzyme-Substrate Complex

The reactant an enzymeenzyme acts on is specifically called the _________.

EnzymeSubstrate Joins

______ ___________ _____• A specific region of an enzymeenzyme molecule which

binds to the substratesubstrate.

EnzymeSubstrate

Active Site

EnzymeAnimation : Gary E. Kaiser http://student.ccbcmd.edu/biotutorials/proteins/enzsub.html

View : http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

An enzyme flick

Let the show begin....

General Types of Enzymes

• Amylases –

break starch to glucose

• Lipases –

break lipids to fatty acids and glycerol

• Proteases –• break proteins to

amino acids

• Nucleases – break nucleic acids DNA and RNA to nucleotides

Shape of a Protein

• An enzyme fits with its specific substrate like a “lock and key”

How Do You Stop an Energizer Enzyme?

DENATURE IT!

Means it loses its 3D shape

4 levels of Protein Structure

Factors Affecting Enzyme Activity

• Temperature

• pH

• Cofactors & Coenzymes

• Inhibitors

Temperature & pH

• Enzymes work best at specific temperatures

• This is why very high fevers are so dangerous. They can This is why very high fevers are so dangerous. They can cook the body’s proteinscook the body’s proteins

• Enzymes usually work best between pH 6 - 8

Coenzymes & Cofactors

• Molecules that are needed by the enzyme to work properly.

• Many are vitamins and mineral substances substances (zinc, iron, (zinc, iron, copper, vitaminscopper, vitamins))

Image:

EnzymeCofactor : Public domain Wiki, Ribbon-diagram showing carbonic anhydrase II. The grey sphere is the zinc cofactor in the active site.

Diseases due to enzyme damaged or missing

• Lactose intolerance Phenylketonuria

• Lacking lactase Phenylalanine hydroxylase

Enzyme InhibitorsEnzyme Inhibitors

Chemicals that resembleresemble an enzyme’s enzyme’s normal substrate normal substrate and competecompete with it for the active siteactive site.

Enzyme

Competitive inhibitor

Substrate

1. Competitive inhibitors:1. Competitive inhibitors: Resembleesemble an enzyme’s normal substrate enzyme’s normal substrate and

competecompete with it for the active siteactive site.

Image: Competitive Inhibition : www-biol.paisley.ac.uk/.../chapter3_2.html

Inhibitors can also attach to Inhibitors can also attach to another part another part of the enzymeenzyme causing the enzymeenzyme to change the shape of change the shape of its active site.its active site.

If its shape changes..it no longer If its shape changes..it no longer works!works!

Enzyme

active site altered

NoncompetitiveInhibitorSubstrate

Enzyme InhibitorsEnzyme Inhibitors

Blocking an bacteria’s enzymes can kill it

Many antibiotic drugs are enzyme inhibitors.

Enzyme inhibitors are also used as weed and bug killers

Images

Dead Bug : www.kansas.gov/help_center/user_testing.html

Prescription Drugs : www.patentdocs.us/.../08/by-kevin-e-noon.html

Enzymes are ____ ________ in the reactions they catalyze.

Think of them as tiny machines in manufacturing.

The more machines, the faster the accumulation of _________.

Image:

Wine Bottling : www.morrison-chs.com/timingscrews/index.html

Wine Vats: www.lymebaywinery.co.uk/pages/about_us.htm

Formats for writing a chemical reaction.

( ________ )

_______ + ________ -----------> _________

( ________ )

__________ -----------> ________ ________

Coenzyme : Vitamin B12

• ExampleExample::

Most _________ are coenzymes essential in helping move atoms between molecules in the formation of carbohydrates, fats, and proteins.

• Exclusively synthesized by ___________ (found primarily in meat, eggs and dairy products).

Image: VitaminB12 : NIH, Public Domain www.nlm.nih.gov/.../ency/imagepages/19516.htm

Featured Enzyme #1: Catecholase

• Catecholase is present in most ______ and __________.

• It is the enzyme that facilitates the ________ of cut or bruised fruits and vegetables by catalyzing the following reaction:

(______________)

_________ + _____ ----------------- _____________ colorless substrate brown product

Featured Enzyme #1: Catecholase & Noncompetetive Inhibition

_________ juice and other acids are used to preserve color in fruit, particularly apples, by lowering the ____ and removing the copper site (cofactor)necessary for the enzyme to function.

catecholase

catechol + O2 -------------------------- polyphenol colorless substrate brown product

Featured enzyme #2: Bromelain• Pineapple contains enzyme bromelain, which can

_______ _________.

• Jell-O is made of gelatin, a processed version of a structural protein called _________ that is found in many animals, including humans.

• Collagen big, fibrous molecule makes skin, bones, and tendons both strong and elastic.

• Gelatin you eat in Jell-O comes from the collagen in cow or pig bones, hooves, and connective tissues. (Yummie!)

• Examine 2 containers:

a. In one, canned pineapple was used to make jello.

b. The other, fresh pineapple was used.

http://www.think-bank.com/iwb/flash/enzymetale.html