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
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Heat
Glucose
Oxygen
Chemical reactions
ATP ATP
Energy for cellular work
Carbon dioxide
Water
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
Energy Capture
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Energy flow:Sun producers consumers decomposers
and Bacteria
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Energy Flow Through Ecosystems
Two ways for organisms to capture energyProducers - produce chemical energy from
energy in sunlight
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Energy Flow Through Ecosystems
Two ways for organisms to capture energyProducers - produce chemical energy from
energy in sunlightConsumers - 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_web.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
Energy in Living Systems
Metabolismis the sum of all chemical reactions in the body.Characteristic of Living ThingsTransfers 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 H2OREACTANTS PRODUCT
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Chemical reactions
H H
H2 +
O O
O2
OH H
H2O
H H
2
OH H
2
REACTANTS?PRODUCTS?
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Chemical reactions
H H
H2 + NH3
H H
H
N
N2
N N
H H
3
H H
2
H H
H
N
REACTANTS?PRODUCTS?
Types of Chemical Reactions
ENDERGONIC Require an input of
energy from the surroundings
Yield products rich in potential energy
Example: photosynthesis
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Reactants
Products
Amount ofenergy
required
Pote
ntia
l ene
rgy
of m
olec
ules
Energy required
Types of Chemical Reactions
EXERGONIC Release energy Yield products that
contain less potential energy than their reactants
Examples: cellular respiration, burning
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Energy releasedPo
tent
ial e
nerg
y of
mol
ecul
es
Reactants
Products
Amount ofenergy
released
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
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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CO2
glucose e–
oxygen H+
e–
water
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
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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.H2O2H2O+ O2
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substrate products
“Gets turned into”Chemical Reaction
Catalyzed by enzyme
Activation Energy
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Reactants
Netchangein energy
EAwithoutenzyme
Products
Progress of the reaction
Ener
gy
EAwithenzyme
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
Phosphategroup
P P P
H2O
Hydrolysis
ATP ADPRibose
Adenine
Adenosine diphosphate
P P P Energy
How does ATP work?
Adenosine Triphosphate
Phosphategroup
P P P
H2O
Hydrolysis
ATP ADPRibose
Adenine
Adenosine diphosphate
P P P Energy
How does ATP work?
ATP powers cellular work through coupled reactionsThe 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
P P
P
P
P
P
PADP
Reactants
Product
Molecule formed Protein moved Solute transported
Motorprotein
Membraneprotein Solute
ATP regenerates The ATP cycle involves continual
phosphorylation and hydrolysis
Energy fromexergonicreactions
ATP
ADP P
Energy forendergonicreactions
Hydroly sis
Phos
p ho y
lat io
n
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”
More complex version: polar/nonpolar, hydrogen bonds, shape, other interactions between atoms
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Carboxypeptidase
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 B C D(initial reactant) (intermediates) (final product)
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Wow!
A single enzyme may act on thousands or millions of substrate molecules per second
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Animation – Campbell Ch 5: How Enzymes Work
Example Enzyme Reaction
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Enzyme availablewith empty activesite
Active site
Glucose
Fructose
Products arereleased
Enzyme(sucrase)
Substrate(sucrose)
H2O
Substrate isconverted toproducts
Substrate bindsto enzyme withinduced fit
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
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•Enzymes function best at one pH and temperature•What conditions do you think an enzyme would function best at?
Enzyme Activity
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Human Enzyme (37°C)
Heat-Resistant BacteriaEnzyme (70°C)
Pepsin (stomach)
Trypsin (small intestine)
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!
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Animation:Egg WhiteEgg WhiteDenaturationDenaturation
Enzyme Inhibitors
A COMPETITIVE inhibitor takes the place of a substrate in the active site
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Substrate
Enzyme
Active site
Normal binding of substrate
Competitiveinhibitor
Noncompetitiveinhibitor
Enzyme inhibition
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
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Substrate
Enzyme
Active site
Normal binding of substrate
Competitiveinhibitor
Noncompetitiveinhibitor
Enzyme inhibition
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 disease-causing 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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