ENERGY!!!!!
WHERE DOES IT
COME FROM??????
What do you think of when you
think of a chemical reaction?
Chemical Reactions
Change substances into different
substances by breaking and
forming chemical bonds.
Can you name any reactions.
NaHCO3(s) +HC2H3O2(aq) =>H2O +
CO2(g) + NaC2H3O2(aq)
Can You Think of Any Reactions in
Your Body?
Where to you think oxygen and carbon
dioxide come from?
Chemical Equations

Needs energy
to start
reactions!!!
REACTANTS
PRODUCTS
Parts of an Equation
All chemical reactions…
have two parts:
1.
2.


Reactants = the substances you start with
Products = the substances you end up with
The reactants will turn into the
products.
Reactants  Products

TAKES ENERGY TO GET A REACTION
GOING!! Most of the time!!

What gets photosynthesis going?
Where does the energy come from?
Where does energy exist in the equation?


Basic Revision

For a chemical reaction to occur, bonds must
be both formed and broken

Fe + CuSO4
Cu + FeSO4
Bond Energy



BOND ENERGY :Amount of energy needed
to break the bonds between molecules.
Energy is needed to break bonds. The stronger
the bond the more energy needed. The
amount of energy is different for all bonds.
Energy is released when bonds are formed
like with H and O to make water.
Activation Energy
Energy needed to get the reaction
started.
Photosynthesis: sunlight
Fuel: match
Bond Energy
If the SAME NUMBER of bonds are made and broken, how can
energy be given out in an exothermic reaction?
The answer is that different chemical bonds have different
amounts of energy in them.
Carbon is joined to a hydrogen by a strong bond. 412 kJ of
energy is needed to break this bond, and to separate the
atoms The same amount of energy is given out when the bond
is formed.
H
O has a bond energy of 463
kJ
C==O has a bond energy of 743
kJ
Chemical Reaction either absorb or
release energy
Reactants: energy needed to break bonds. Energy
added to break bonds.
Products: form bonds so energy is released.
If subtract the amount of energy released and
needed, sometimes there if more energy
released and other times there is energy
absorbed
Exothermic and Endothermic
Reactions

A reaction in which heat or more energy is
produced is given out is exothermic.

A reaction in which heat is taken in or more
energy is used is endothermic.
Exothermic Reactions
Energy is needed to break bonds
apart.
Energy is released when bonds
are formed.
So how do exothermic reactions give
out energy to the surroundings?
ENERGY AND CHEMICAL
REACTIONS
Exothermic reactions
 These reactions give out heat energy.
 Combustion is an exothermic reaction.
Exothermic reactions




Chemical reaction where more energy is
released than it absorbs
Difference in energy between reactant and
products.
Usually heat or light.
EX: Cellular respiration
Energy Level Diagrams
These are drawn as graphs.
They are used to show exothermic and
endothermic reactions.
The x axis shows time, the y axis shows energy.
Energy
Time
Activation Energy
Most exothermic reactions need a bit of energy to get them started,
like lighting methane with a match.
This energy is known as ACTIVATION ENERGY. This
energy breaks the bonds and allows atoms to separate.
This changes the shape of the energy diagram to this.
reactants
} Activation energy
Energy
products
Time
Exothermic Reactions
An exothermic energy diagram looks like this.
reactants
Energy
products
Time
}
Energy released
Exothermic Reactions
Combustion and respiration are exothermic reactions.
e.g. burning methane (natural gas).
CH4 + 2O2 
2H2O
+ CO2
CH4 + 2O2
Energy
2H2O + CO2
Time
}
Energy released
Exothermic Reaction
ENERGY AND CHEMICAL
REACTIONS
Endothermic reactions
 These reactions take in heat energy from their
surroundings.
 These cause temperatures to fall. They get
cold!!!
Endothermic Reactions
In these reactions, the energy required for
bond breaking IS GREATER than the energy
released by bond making.
This means that to make endothermic
reactions take place, extra energy is needed
from an external source.
Endothermic reactions



Chemical reaction where more energy is
absorbed than released.
Energy must be absorbed to make up
difference between reactants and products
EX: photosynthesis Traps energy in bonds of
glucose
Endothermic Reactions
Examples are photosynthesis and most electrolysis reactions.
The energy level diagrams look like this.
products
Energy
reactants
Time
}
Energy needed
to make the
reaction work.
Endothermic Reaction
When trying to classify a process as exothermic or endothermic, watch how the
temperature of the surroundings changes. An exothermic process releases heat, and
causes the temperature of the immediate surroundings to rise. An endothermic process
absorbs heat and cools the surroundings. Can you think of a way to test the classification
of each of these processes?
Exothermic processes - gives off energy
Endothermic processes- takes in
energy
melting ice cubes
conversion of frost to water vapor
evaporation of water
making ice cubes
formation of snow in clouds
condensation of rain from water vapor
a candle flame
mixing sodium sulfite and bleach
baking bread
rusting iron
cooking an egg
burning sugar
producing sugar by photosynthesis
forming ion pairs
separating ion pairs
Combining atoms to make gas
splitting a gas molecule apart
mixing water and strong acids
mixing water and ammonium nitrate
mixing water with an anhydrous salt
crystallizing liquid salts
in chemical handwarmers)
melting solid salts
nuclear fission reaction of barium hydroxide octahydrate crystals with dry ammonium ch
Activation Energy

Energy needed to get the reaction started.
Some reaction takes more energy than others.
Usually this is increasing the temperature but
organisms cannot change the temperature so
something else has to help decrease the
amount of energy needed. We cannot use all
our energy for reactions like photosynthesis
and respiration.
Increase of Temperature



Can organisms have a great increase in
temperature?
Need other ways to get increase or to decrease
the amount of activation energy needed
This is where catalysts come into play.
CATALYST



A substance that decreases the activation
energy needed to start a reaction. Usually
temperature increase but organisms cannot
have a great increase in temperature or die
Increases the rate of reaction or speed of
reactions.
They break the bonds between the reactants to
speed up the reaction.
Enzymes
36
ENZYMES
*A type of protein that acts as a catalyst which
lowers activation energy needed to start a
reaction.
*They speed up reactions by weaken bonds.
*Always in in -ase
© 2007 Paul Billiet ODWS
What Are Enzymes?
Most enzymes are
Proteins (tertiary
and quaternary
structures)
 Act as Catalyst to
accelerates a
reaction
 Not permanently
changed in the
process

38
How do enzymes Work?
Enzymes work
by weakening
bonds which
lowers
activation
energy
39
Enzyme structure



Enzymes are
proteins
They have a
globular shape
A complex 3-D
structure
.
© 2007 Paul Billiet ODWS
Enzymes
Are specific for
what they will
catalyze
 Are Reusable
 End in –ase
-Sucrase
-Lactase
-Maltase

41
The substrate




The substrate of an enzyme are the reactants
that are acted on by the enzyme.
Enzymes are specific to their substrates
The specificity is determined by the active
site
ENZYMES ARE SHAPED TO FIT ONLY
THEIR SUBTRATE BECAUSE THEIR
ACTIVE SITE IS SHAPED TO FIT ONLY
ONE SUBSTRATE!!!!
© 2007 Paul Billiet ODWS
The active site
PLACE WHERE
SUBSTRATE FITS!!
ONLY THE ONE
SUBTRATE WILL
FIT!!!
© H.PELLETIER, M.R.SAWAYA
ProNuC Database
© 2007 Paul Billiet ODWS
Enzyme Structure




It fits like a lock and key with its subtrate.
Will not fit any other substance.
How Works
1. Enzyme brings molecules close together.
2. By bonding they have weaken the bonds of
the subtrate so they reaction can occur
quicker.
An enzyme controlled pathway
© 2007 Paul Billiet ODWS
The Lock and Key Hypothesis




Fit between the substrate and the active site of the
enzyme is exact
Like a key fits into a lock very precisely
The key is analogous to the enzyme and the substrate
analogous to the lock.
Temporary structure called the enzyme-substrate
complex formed
© 2007 Paul Billiet ODWS
The Lock and Key Hypothesis


This explains enzyme specificity
This explains the loss of activity when
enzymes denature
© 2007 Paul Billiet ODWS
Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
48
49
Enzyme-Substrate
Complex
The substance (reactant) an enzyme
acts on is the substrate
Substrate
Joins
Enzyme
50
Active Site

A restricted region of an
enzyme molecule which binds
to the substrate.
Active
Site
Substrate
Enzyme
51
Induced Fit


A change in
the shape of
an enzyme’s
active site
Induced by
the substrate
52
Induced Fit


A change in the configuration
of an enzyme’s active site (H+
and ionic bonds are involved).
Induced by the substrate.
Active Site
substrate
Enzyme
induced fit
53
What Affects Enzyme
Activity?

Three factors:
1.Environmental Conditions
2.Cofactors and Coenzymes
3.Enzyme Inhibitors
54
Denaturing of Enzymes

1.
2.
3.
Denaturing: enzyme structure can be
destroyed by many different factors.
pH
Temperature
Inhibitors(like poison)
1. Environmental Conditions
A. Extreme Temperature are the
most dangerous high temps may
denature (unfold) the enzyme.
B. pH (most like 6 - 8 pH near
neutral)
C. Ionic concentration (salt ions)
56
The effect of temperature




For most enzymes the optimum temperature is about
30°C
Many are a lot lower,
cold water fish will die at 30°C because their
enzymes denature
A few bacteria have enzymes that can withstand very
high temperatures up to 100°C
Most enzymes however are fully denatured at 70°C
© 2007 Paul Billiet ODWS
The effect of temperature
Q10
Enzyme
activity
0
© 2007 Paul Billiet ODWS
10
20
30
40
Temperature / °C
Denaturation
50
The effect of pH





Extreme pH levels will produce denaturation
The structure of the enzyme is changed
The active site is distorted and the substrate
molecules will no longer fit in it
At pH values slightly different from the enzyme’s
optimum value, small changes in the charges of the
enzyme and it’s substrate molecules will occur
This change in ionisation will affect the binding of
the substrate with the active site.
© 2007 Paul Billiet ODWS
Enzymes work in different pH

All enzymes can work in different conditions
Intestines would have a lower pH than mouth.

Look at website for examples!!!!!!

The effect of pH
Optimum pH values
Enzyme
activity
Trypsin
Pepsin
1
© 2007 Paul Billiet ODWS
3
5
7
pH
9
11
2. Cofactors and Coenzymes


Inorganic substances (zinc, iron) and
vitamins (respectively) are sometimes
need for proper enzymatic activity.
Example:
Iron must be present in the
quaternary
structure hemoglobin in order for it to
pick up oxygen.
62
Inhibitors




Inhibitors are chemicals that reduce the rate of
enzymic reactions.
The are usually specific and they work at low
concentrations.
They block the enzyme but they do not
usually destroy it.
Many drugs and poisons are inhibitors of
enzymes in the nervous system.
© 2007 Paul Billiet ODWS
Two examples of Enzyme
Inhibitors
a. Competitive inhibitors: are
chemicals that resemble an
enzyme’s normal substrate and
compete with it for the active
site.
Substrate
Competitive inhibitor
Enzyme
64
Inhibitors
b. Noncompetitive inhibitors:
Inhibitors that do not enter the active
site, but bind to another part of the
enzyme causing the enzyme to change its
shape, which in turn
alters the
active site.
Substrate
active site
altered
Enzyme
Noncompetitive
Inhibitor
65
Metabolic Enzymes
Metabolic enzymes run all the body organs and
systems by performing various chemical
reactions within the body cells. Catalase, which
breaks down hydrogen peroxide, a metabolic
waste product, liberating the oxygen for use in the
body..
http://highered.mcgraw-hill.com/sites/0072495855/student_
view0/chapter2/animation__how_enzymes_work.html
Digestive enzymes are secreted by the body to
digest the food eaten.
There are three categories of digestive
enzymes:
• Amylases (found in saliva, the pancreas, and
intestinal juices) break down carbohydrates; •
Proteases (found in the stomach, pancreatic,
and intestinal juices) help digest protein; •
Lipases (pancreatic juices, and in food fats) aid
in fat digestion. •
•Amylase enzymes are found in the saliva and in the
juices of the pancreas and intestinal tract and help the
digestive process by breaking down carbohydrates.
There are different kinds of amylase. For example, the
enzyme sucrase breaks down the sugar sucrose found
in cane and beet sugar. The enzyme lactase breaks
down the lactose sugar in milk. The enzyme maltase
breaks down the malt sugar maltose.
•Protease enzymes are found in the juices of the
pancreas, the stomach and the intestinal tract and help
with the breakdown and the digestion of proteins.
•Lipase enzymes are found in the juices of the stomach
and pancreas and help to break down fats.