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Energy and Enzymes
Energy in Living Systems
Energy is the capacity to perform work
 Energy can be converted from one form to
another

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Energy in Living Systems

KINETIC ENERGY is
the energy of motion
 Includes
light
 Includes heat
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Energy in Living Systems

POTENTIAL
ENERGY is the
energy stored in a
location or structure
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Energy in Living Systems


POTENTIAL
ENERGY is the
energy stored in a
location or structure
Molecules have
potential energy
called CHEMICAL
ENERGY
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Energy in Living Systems

Cells convert KINETIC ENERGY to
POTENTIAL ENERGY and back.
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Thermodynamics

1st law: Energy can be
changed from one
form to another, but
cannot be created or
destroyed.
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Thermodynamics

2nd law: Energy transformations increase
disorder, or entropy, and some energy is lost
as heat
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Laws of Thermodynamics in
Organisms

As energy is converted from one form to another,
heat is lost
Heat
Chemical reactions
Carbon dioxide
Glucose
ATP
ATP
Water
Oxygen
Energy for cellular work
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Energy Flow Through
Ecosystems

Energy flows in one
direction through
ecosystem
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Majority of Energy is from the
SUN

Amount of energy
captured by plants
influences the
ecosystem
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Energy Capture
Energy
flow:
Sun  producers  consumers  decomposers
and Bacteria
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Energy Flow Through Ecosystems

Two ways for organisms to capture energy
 Producers
- produce chemical energy from
energy in sunlight
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Energy Flow Through Ecosystems

Two ways for organisms to capture energy
 Producers
- produce chemical energy from
energy in sunlight
 Consumers - consume other organisms for
energy
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Food webs - the reality
**Arrows show energy
flow, not who eats who
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Food web creation

http://www.gould.edu.au/foodwebs/kids_w
eb.htm
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Energy Pyramid



Energy flows through
food chain
Most energy lost as
metabolic heat
Each step is a trophic
level
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Concentration of toxins




As you go up the
energy pyramid,
toxins build up in
bodies of animals
“Bioaccumulation”
and “biomagnification”
Example: DDT
Example: Mercury
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Energy in Living Systems

Metabolismis the sum of all chemical
reactions in the body.
 Characteristic
of Living Things
 Transfers energy and follows the laws of
thermodynamics.

Chemical Reactions store or release
energy
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Chemical Reactions
Reactants interact, leading to products
 Atoms are rearranged, but the number of
atoms stays constant on both sides of the
equation

H2 + O2 H2O
REACTANTS
PRODUCT
Chemical reactions
2 H2
H H
+
O2
O
O

2 H2O
H
H
O
H H
REACTANTS?
PRODUCTS?
H
H
O
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Chemical reactions
3 H2
H H
+

N2
N
H
N
N
H H
H H
2 NH3
H
REACTANTS?
PRODUCTS?
H
H
N
H
H
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Types of Chemical Reactions
Products
Potential energy of molecules
ENDERGONIC
 Require an input of
energy from the
surroundings
 Yield products rich in
potential energy
 Example: photosynthesis
Energy required
Amount of
energy
required
Reactants
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EXERGONIC
 Release energy
 Yield products that
contain less potential
energy than their
reactants
 Examples: cellular
respiration, burning
Potential energy of molecules
Types of Chemical Reactions
Reactants
Energy released
Amount of
energy
released
Products
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Using Energy from Food


Energy transfer in
cells must be
controlled
Reactions are
carefully controlled
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Uncontrolled Reaction



Glucose and Oxygen
react when exposed
to a spark
Energy is released all
at once
CO2 and H2O form
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Controlled Reaction

CO2
e–
glucose
oxygen

H+

e–
water

Energy input used to
split glucose
Same overall reaction
occurs, but in small
steps
Energy can be
harnessed to do work
in cell
CO2 and H2O form
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Enzymes


Proteins
Perform and control
chemical reactions

Why are enzymes
important?
 Digestion
 Building
/ recycling cells
 Muscle contraction
 Everything that happens
in your body
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Enzymes
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Enzyme Examples



Lactase – cleaves
lactose sugar
DNA Polymerase –
joins nucleotide
monomers to make
DNA polymer
Luciferase –
generates light in
fireflies



Amylase – breaks
down starch during
digestion
Protease – breaks
down proteins
Cellulase – breaks
down cellulose
(bacterial enzyme
found in ruminants)
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Interesting Enzyme Example

A Hope For Oil Spill
Bioremediation
ScienceDaily (May 17,
2005) — A recently
published article in
Environmental
Microbiology reveals
that indigenous
microbiota of the
Galician shore is readily
able to degrade crude
oil.

What are the
consequences of this
discovery?
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Enzymes

“Catalysts”
 speed
up a reaction,
but aren’t used up
 Can be used over and
over in the cell
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Enzymes

Enzymes are not
altered in a reaction
and can be used
again (catalyst)

Lew-Port Enzyme
Animation
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Reactions and Enzymes


Some chemical reactions need a “jump start” in
order to proceed
Energy needed to jump start a reaction is called
activation energy
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Reactions and Enzymes



Glucose contains energy
in its bonds
Energy is released when
bonds are broken
Small amount of energy
must be expended to
start reaction
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Enzymes
Work by lowering the activation energy.
 Reactants the enzyme acts upon are
called substrates.
H2O2H2O+ O2

substrate
products
“Gets turned into”
Chemical Reaction
Catalyzed by enzyme
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Activation Energy
EAwithout
enzyme
EAwith
enzyme
Reactants
Net
change
in energy
Products
Progress of the reaction
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Where does the energy come
from?


ATP is a form of
chemical energy the
cell can use
ATP (adenosine
triphosphate) powers
nearly all forms of
cellular work
Where does the energy come
from?


ATP is composed of
one adenine, one
ribose, and three
negatively charged
phosphates
The energy in an ATP
molecule lies in the
bonds between its
phosphate groups
How does ATP work?
Adenosine
Triphosphate
Phosphate
group
P
Adenine
P
P
Adenosine diphosphate
H2O
P
Hydrolysis
Ribose
ATP
ADP
P
+
P
+
Energy
How does ATP work?
Adenosine
Triphosphate
Phosphate
group
P
Adenine
P
P
Adenosine diphosphate
H2O
P
Hydrolysis
Ribose
ATP
ADP
P
+
P
+
Energy
How does ATP work?

ATP powers cellular work through coupled
reactions
 The
bonds connecting the phosphate groups
are broken by hydrolysis, an exergonic
reaction (absorbs or releases energy?)
 Hydrolysis is coupled to an endergonic
reaction through phosphorylation
 A phosphate group is transferred from ATP to
another molecule
ATP
Chemical work
Mechanical work
Transport work
Membrane
protein
P
Motor
protein
Solute
P
Reactants
P
P
P
Product
Molecule formed
P
Protein moved
ADP + P
Solute transported
ATP regenerates

The ATP cycle involves continual
phosphorylation and hydrolysis
ATP
Energy from
exergonic
reactions
Energy for
endergonic
reactions
ADP +
P
Enzymes



Very specific for
reactions
Three dimensional
shape determines
function (remember
the World’s Largest
Protein)
Active site is region
where the substrate
binds
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“Lock and Key”

Easy version:
Enzyme and
substrate fit like a lock
and key (shape)
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“Lock and Key”

Carboxypeptidase
More complex
version:
polar/nonpolar,
hydrogen bonds,
shape, other
interactions
between atoms
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Enzymes in Metabolism
Metabolic pathways in the body usually
involve several reactions.
 There may be several intermediates.
 Each intermediate has its own enzyme.

E1
E2
E3
A
(initial reactant)
B
(intermediates)
C
D
(final product)
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Wow!

A single enzyme may act on thousands or
millions of substrate molecules per second
Animation – Campbell Ch 5:
How Enzymes Work
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Example Enzyme Reaction
Enzyme available
with empty active
site
Active site
Glucose
Substrate
(sucrose)
Enzyme
(sucrase)
Substrate binds
to enzyme with
induced fit
Fructose
H2O
Products are
released
Substrate is
converted to
products
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Cellular Environment Affects
Enzymes

Some enzymes require non-protein
cofactors


Metal ions, organic molecules called coenzymes
Physical factors influence enzyme activity

Temperature, salt concentration, pH
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Enzyme Activity
•Enzymes function best at one pH and temperature
•What conditions do you think an enzyme would
function best at?
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Enzyme Activity
Human Enzyme (37°C)
Heat-Resistant Bacteria
Enzyme (70°C)
Trypsin (small intestine)
Pepsin (stomach)
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Altering Enzymes


For all proteins: change of shape may change
the function.
Denatured = major change in structure due to
external stress
 Breaks
hydrogen bonds
 Temperature
 pH
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Denaturation
Of a protein
DNA does it too!
Animation:Egg White
Denaturation
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Enzyme Inhibitors

A COMPETITIVE
inhibitor takes the
place of a substrate in
the active site
Substrate
Active site
Enzyme
Normal binding of substrate
Competitive
inhibitor
Noncompetitive
inhibitor
Enzyme inhibition
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Enzyme Inhibitors


A COMPETITIVE
inhibitor takes the
place of a substrate in
the active site
A NONCOMPETITIVE
inhibitor alters an
enzyme's function by
changing its shape
Substrate
Active site
Enzyme
Normal binding of substrate
Competitive
inhibitor
Noncompetitive
inhibitor
Enzyme inhibition
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Enzyme Inhibitors

Cyanide inhibits an
enzyme involved with
ATP production
during cellular
respiration
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Enzyme Inhibitors

Some pesticides
irreversibly inhibit an
enzyme crucial for
insect muscle function
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Enzyme Inhibitors

Many antibiotics
inhibit enzymes
essential for diseasecausing bacteria
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Enzyme Inhibitors

Ibuprofen and aspirin
inhibit enzymes
involved in inducing
pain
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Enzyme activity #1 – to turn in





Design an enzyme that
could function in this
environment 
Determine the organism it is
found in
Determine the substrate
and draw the enzyme /
substrate complex
Give it an appropriate name
Draw graphs of its activity at
different pH and
temperatures
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Enzyme activity #2 – to turn in



Pepsin cleaves proteins
into their component
amino acids during
digestion
Use ecology vocabulary
to describe organisms
that would produce high
levels of pepsin
Draw graphs of its activity
at its optimum pH and
temperatures
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