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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