Organic Reactions and
Enzymes
Warmup (9/22)

Watch the video and answer the following
questions
http://www.youtube.com/watch?v=9X-BtcjOTus



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What is the purpose of pasteurization?
Describe two types of pasteurization.
Why is it important to eat whole (raw) fruits and vegetables?
Why are preservatives added to juice, even after
pasteurization?
Enzymes
 Are
PROTEINS
 Function as
Biological
catalysts (get reaction
started!)
 Speed
up the
reaction by
lowering the
activation energy
Enzyme action

Enzymes have a
particular shape.

Provides a “binding site”,
a place where the
substrate (reactant) fits in
like a lock and key
 then the reaction
happens

Shape of enzyme’s
binding (active)
site is very
specific—only fits
one substrate
Enzymes are Sensitive!

Specific conditions are required for an
enzyme to function:

Most will only work within a particular range of:
 Temperature
 pH


(acidity)
At high temperatures, an enzyme may degrade
(break down). (Think pineapple and Jell-O)
This helps to regulate enzyme function

Enzymes only cause the reaction to happen
when the conditions are right. Human body?
How enzymes are named

Each is usually named for the reaction it
catalyzes
Protease = breaks down protein
 Anhydrase = removes water


If you know the name, you can often figure
out the function!
 Are
Enzymes
specific for
what they will
catalyze
 Are Reusable
 End in –ase
-Sucrase
-Lactase
-Maltase

http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter
2/animation__how_enzymes_work.html
7
Chemical Reactions
Changing of one set of chemicals into a new
set of chemicals
 A chemical change
 Always involve the breaking of chemical
bonds and/or the formation of new bonds
 Examples:

CH4 + O2  CO2 + H2O (This is not balanced)
 2H2 + O2 2H2O


Intro to enzymes
http://ffh.films.com/PreviewClip.aspx?id=171
63
How do enzymes Work?
Enzymes work by
weakening
bonds which
lowers
activation
energy
11
HOW ENZYMES WORK
• Enzymes are ORGANIC
CATALYSTS. A CATALYST is
anything that speeds up a
chemical reaction that is
occurring slowly.
How does a catalyst work?
• The explanation of what
happens lies in the fact that
most chemical reactions that
RELEASE ENERGY
(exothermic reactions) require
an INPUT of some energy to
get them going. The initial
input of energy is called the
ACTIVATION ENERGY
Energy in Reactions



Reactions can release or absorb energy
Reactions that release energy (exothermic)can
occur spontaneously, however, many need
Activation energy
Activation energy is energy needed to get a
reaction started
Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
14
Energy in reactions cont.

Chemical reactions that absorb energy
(endothermic) generally need much
activation energy
pH Scale
• Let’s get pHunky
You may know…
• Chemists measure how acidic or basic a
substance is with…
The pH scale
• Acid and base strength is
measured on a pH scale that ranges
from 0 to 14
• Neutral solutions have a pH = 7
• Acidic solutions have a pH < 7
• Basic solutions have a pH > 7
Acids
• These substances have extra H+ ions
• Below 7 = acid
• pH indicates the amount of Hydrogen ions
in a solution
It’s the pOWER of
Hydrogen, phools!
Bases
• These solutions have fewer H+ in the
substance (and more OH- ions)
• Base is anything > 7
• Aka alkaline
• Neutral substances= 7
pHun with the pH scale
Just remember this brothers and sisters:
ABBA
Why is this chemistry important in biology class?
• Your body-
HOMEOSTASIS!!!!!!!!
– Stomach acids help digest
food
– Blood – pH of about 7
(neutral)
– Enzymes function only at
specific pH
Why is this chemistry important in biology class?
• Environment
– Acid rain
– Water pollution
Acid Rain Effects
Application: How does pH affect
an enzyme?
• Look at “Analyzing Data” section on page
51 in your textbook.
– Answer questions #1-6
Homework (due Wed 9/28)

Write out the answers to all Chapter 1 and 2
Learning Targets
Must write in complete sentences
 Do this in your lab book, after the McMush
conclusion questions
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