Chpt. 8 An Intro to Metabolism

Chpt. 8

An Intro to Metabolism

Metabolism-

totality of an organism’s chemical

reactions

Metabolism-

totality of an organism’s chemical

reactionsmolecules are alteredmolecules are ateredmolecules are ateed

Metabolism-

molecules are altered molecules are atered molecules are ateed

Enzymes catalyze each step

Metabolic Reactions:Types:Catabolic-break down molecules

•release energyex. cellular respiration

Metabolic Reactions:Types:Anabolic-

consume energyex. making proteins from

amino acids

build molecules

Examples • dehydration synthesis (synthesis)

• hydrolysis (digestion)

+

H2O

+

H2O

enzyme

enzyme

Examples • dehydration synthesis (synthesis)

• hydrolysis (digestion)

enzyme

enzyme

HOW ORGANISMS MANAGE THEIR ENERGY

resources

capacity to do work: change in the state or motion of matter

Cells obtain chemical energy when molecules are

rearranged:

Therefore, a basic knowledge of ENERGY is necessary to understand how cells work…

Potential Energy •stored in molecules in the chem. bonds

…is converted to Kinetic Energy

Potential Energy - where is it in this picture?

Kinetic Energy

•(energy of motion)

• energy that “powers” the cell.

ex. cell respiration, releases energy stored in the bonds of sugar

molecules.

Kinetic Energy

Where is it here??? This one is easy to see!

energy transformat

ion

1st Law of Thermodynamics

chemical energy was not chemical energy was not created, and will not be created, and will not be destroyed… but it can destroyed… but it can

change formschange forms

A

B

C

Flow of energy through life• Life is built on chemical

reactions transforming energy from one form to another

organic molecules ATP & organic molecules

organic molecules ATP & organic molecules

sun

solar energy ATP & organic molecules

2nd Law of Thermodynamics

Every energy transfer or Every energy transfer or transformation, increases transformation, increases entropyentropy (disorder) in the (disorder) in the

UniverseUniverse

Christian Right Lobbies To Overturn Second Law Of ThermodynamicsSeptember 6, 2000 | Issue 36•31

TOPEKA, KS–The second law of thermodynamics, a fundamental scientific principle stating that entropy increases over time as organized forms decay into greater states of randomness, has come under fire from conservative Christian groups, who are demanding that the law be repealed.

"What do these scientists want us teaching our children? That the universe will continue to expand until it reaches eventual heat death?" asked Christian Coalition president Ralph Reed, speaking at a rally protesting a recent Kansas Board Of Education decision upholding the law. "That's hardly an optimistic view of a world the Lord created for mankind. The American people are sending a strong message here: We don't like the implications of this law, and we will not rest until it has been reversed in the courts."

The controversial law of nature, which asserts that matter continually breaks down as disorder increases and heat is lost, has long been decried by Christian fundamentalists as running counter to their religion's doctrine of Divine grace and eternal salvation.

"Why can't disorder decrease over time instead of everything decaying?"

2nd Law of Thermodynamics

Every energy transfer or Every energy transfer or transformation increases transformation increases entropy (disorder) in the entropy (disorder) in the

UniverseUniverse

HEAT is a very HEAT is a very DISORDERED form of DISORDERED form of

energyenergy

Chemical reactions & energy

• Some chemical reactions release energy– exergonic– breaking polymers– hydrolysis = catabolism

• Some chemical reactions require input of energy– endergonic– building polymers – dehydration synthesis = anabolism

digesting molecules= LESS organization=lower energy state

building molecules= MORE organization=higher energy state

Living cells,

unavoidable,

convert organized forms of energy to

heat

QuickTime™ and a decompressor

are needed to see this picture.

Get it… convert to HEAT

Now, THAT’s some disordered HEAT!!QuickTime™ and a

decompressorare needed to see this picture.

changes changes that occur that occur on their on their

own…own…

•When When spontaneous spontaneous

processes occur processes occur in a system (an in a system (an

organism), organism), stabilitystability

increasesincreases~ but ~ but in terms of the in terms of the universe, it universe, it decreasesdecreases

•Unstable Unstable systems tend to systems tend to become more become more stable stable spontaneously.spontaneously.

How can we predict How can we predict which changes occur which changes occur

spontaneously, and spontaneously, and which require input which require input

of E. from the of E. from the

outsideoutside? ?

ENERGY, in a system, THAT CAN PERFORM WORK

measure of this free energy

Yale scientist featured in stamp series Gibbs received the first Ph.D. in engineering in the U.S. from Yale in 1863. He later became a

member of the Yale faculty.

G = H - T S free energy

total energy

temp*entropy change

= -

EntropyEntropy = measure of = measure of disorderdisorder

G = H - T S free energy amount

of useable E. to

do work

total potential

energy~

total bond

energy enthal

py

entropy

= -unuseable energy

Not all of the energy Not all of the energy in a system is in a system is

available for workavailable for work

We can use this to We can use this to predict which predict which

changes occur changes occur spontaneously, and spontaneously, and which require input which require input

of E. from the of E. from the

outsideoutside? ?

G = H - T S free energy

total energy

entropy

= -

spontaneous changes, spontaneous changes, decreasedecrease free free energyenergy

Unstable Systems - change

spontaneously, becoming stable systems, and Free Energy Decreases

Endergonic vs. exergonic reactions

exergonic endergonic- energy released- digestion

- energy invested- synthesis

-G

G = change in free energy = ability to do work

+G

Chemical Reactions (2 Chemical Reactions (2 types):types):

Exergonic- proceeds with a net release of free E. G is negative spontaneous

Endergonic- proceeds with a net gain of Energy/ absorbs it

G is positivenonspontaneous

Chemical Reactions (2 Chemical Reactions (2 types):types):

Exergonic- proceeds with a net release of free E.

exergonic- energy released- digestion

-G

Chemical reactions & energy

• Some chemical reactions release energy– exergonic– breaking polymers– hydrolysis = catabolism

• Some chemical reactions require input of energy– endergonic– building polymers – dehydration synthesis = anabolism

digesting molecules= LESS organization=lower energy state

building molecules= MORE organization=higher energy state

Cells “work” three Cells “work” three ways: ways:

•Mechanical work = muscle

contraction

•Transport work = pumping across

membranes

•Chemical work = making polymers

ENERGY SOURCE for the work is ATPATP

Adenine

Ribose sugar

Phosphates

ATP•Adenine (Nitrogen-base)

•Ribose (sugar) Phosphate chain (3)

ATP•Ribose (sugar)

•Phosphate chain (3)

ATP•Phosphate chain (3)

Bond hold Bond hold potential potential energy!!!energy!!!


Bond can be Bond can be broken via. broken via. hydrolysishydrolysis


Unstable b/c Unstable b/c three negative three negative chargescharges

Label the three parts of the ATP molecule below:

ATP + H2O --->

ADP + P + ENERGY

release

- G

the “P” flew off!!!!

ATP + H2O --->

ADP + P + ENERGY

- G

B/C moving to a more stable condition

ATP, when hydrolysized, releases free

energy (energy that is able

to be used)broken

ATP, when hydrolysized,

releases free E. Cell

takes the energy and transfers the

Phosphate to another molecule.

ATP, when hydrolysized, releases free E.

Cell takes the E. and transfers the Phosphate to another molecule.

Phosphorylation!



Cell takes the E. and transfers the Phosphate to another molecule.This molecule is less

stable than the original molecule.

WHAT DOES A graph HAVE TO DO WITH BIOLOGY ???????

A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells…

A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells…

ex. hydrolysis of sucrose: Does occur

spontaneously….

But it would take way too long….

ex. hydrolysis of sucrose:

Energy of Activation - energy required to break bonds (EA) barrier is EXTREMELY high - the reaction will occur only if reactants are heated:

ex. hydrolysis of sucrose:

Energy of Activation EA barrier is EXTREMELY high - the reaction will occur only if reactants are heated:

Enzymes lower EA-

But do not change G


Energy Energy releasereleasedd

Enzymes don’t change


G

Substrate

Active Site Conformational Change





Enzymes are substrate specific

Enzyme

Enzymes are effected by environmental factors:

Enzymes are affected by environmental factors:

TOOTOO MUCHMUCH HeatHeat disrupts H-bonds disrupts H-bonds in the protein in the protein

……remember, remember, enzymes enzymes are PROTEINare PROTEIN

However:However: HeatHeat does does increaseincrease rate of rxrate of rx…. TO A …. TO A POINT POINT


Beyond that temp, speed of reaction drops:

WHAT about pH changes????

pH disrupts H-pH disrupts H-bonds in the bonds in the protein protein


paperosesubstrate

paperase

A B

Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness

Molecules that are bound to the active site

Competitive Competitive InhibitorsInhibitors

Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness



“normal”

“competative”

WHAT does this to to the RX.

RT???

QuickTime™ and aTIFF (Uncompressed) decompressor


How can we “get around” the lower RX RATE???



How can we “get around” the lower RX RATE??? ADD more

substrate

paperosesubstrate

paperase

inhibitor

A B

A B

see the difference





IMPLICATIONS??

Turns out, the pesticide DDT is a noncompetitive inhibitor





paperosesubstrate

paperase

inhibitor A B

A B

“A cell is not just a bag of chemicals with thousands of

different kinds of enzymes and substrates

wandering about randomly.”

Chaos would result if all of a cell’s metabolic pathways were open at the same time… must be regulated

Allosteric

Regulation



• The control of an enzyme complex by the binding of a regulatory molecule.

• Regulatory molecule may stimulatestimulate or inhibitinhibit the enzyme enzyme complexcomplex.

Allosteric Regulation


enzyme complex


regulatory

molecule may

stimulate or

inhibit the

complex

Allosteric Regulation-•allosteric enzymes have 2 or more polypeptides.

•Oscillates between active and inactive.

•activator keeps it “on” - active

•inhibitor keeps it “off” - inactive

Cooperativity-•Enzyme having many subunits

•Binding of one substrate to the active site causes all active sites to “run”

Feedback Inhibition-•pathways are switched on and off by the end product.

•the end product acts as an inhibitor of an enzyme within the pathway.



Sometimes enzymes require nonprotein “helpers”

CoEnzymesCoEnzymes

Molecules that are bound to the active site



Summary of chpt. 8

•Recognize that Life must follow the Laws of Thermodynamics.

•The role of ATP in cell energy.

•How enzymes work & all senarios in which they can be placed… what is the result?

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Chpt. 8 An Intro to Metabolism

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