Free EnergyAll living systems require constant input of free energy

Metabolism• Metabolism: the sum total of all the chemical reaction that take place to build up and break down the

materials needed in an organism• Catabolism: the breaking down of complex molecules

• Exergonic: aka Spontaneous – happens on its own w/o energy• Releases energy to surroundings/products are more stable than reactants• ∆G = -• Increases disorder (more entropy)

• Anabolism: building complex complex molecules • Endergonic: aka Nonspontaneous – requires energy to take place• Stores or absorbs energy from surroundings/products are less stable than reactants • ∆G = +• Decreases Disorder (less entropy)

• Metabolic pathways: begin with specific molecule, altered in a series of defined steps, resulting in certain products

Enzyme 1 Enzyme 2 Enzyme 3DCBA

Reaction 1 Reaction 3Reaction 2Startingmolecule

Product

Reactants

Energy

Fre

e en

erg

y

Products

Amount ofenergyreleased(∆G < 0)

Progress of the reaction

(a) Exergonic reaction: energy released

Products

ReactantsEnergy

Fre

e en

erg

y

Amount ofenergyrequired(∆G > 0)

(b) Endergonic reaction: energy required

Progress of the reaction

Fig. 8-6a

Energy

(a) Exergonic reaction: energy released

Progress of the reaction

Fre

e en

erg

y

Products

Amount ofenergyreleased(∆G < 0)

Reactants

Fig. 8-6b

Energy

(b) Endergonic reaction: energy required

Progress of the reaction

Fre

e en

erg

y

Products

Amount ofenergyrequired(∆G > 0)

Reactants

Forms of Energy• Kinetic Energy: motions – can do work by transferring motion to other matter (ex: pool

stick – ball to ball)• Thermal energy: type of kinetic energy; aka heat; random movement of atoms or

molecules• Anytime bonds are broken there is a transfer of energy from the molecule to

thermal energy (called heat – this is why we say heat is released to the environment through the food chain – when glucose is broken down in the presences of oxygen bonds are broken some of the energy stored in the bonds of the glucose molecule becomes thermal energy this thermal energy is either lost to the environment OR if the organisms is an endotherm (relies on internal temperature control vs external (ectotherm)) the heat is used to maintain the organisms temperature (called thermoregulation)

• Potential Energy: energy matter posses because its location or structure• Chemical energy: potential energy available for release in a chemical reaction

Climbing up converts the kineticenergy of muscle movementto potential energy.

A diver has less potentialenergy in the waterthan on the platform.

Diving convertspotential energy tokinetic energy.

A diver has more potentialenergy on the platformthan in the water.

Application

Describe the forms of energy found in an apple as it grows on a tree, then falls and is digested by someone who eats it.

Application Answer

• The apple has potential energy in its position hanging on the tree, and the sugar and other nutrients it contains have chemical energy. The apple has kinetic energy as it falls from the tree to the ground. When the apple is digested and its molecules broken down, some of the chemical energy is used to do work, and the rest is lost as thermal energy

• Who knew…so many types of energy in one little apple!!!

Thermodynamics

• Thermodynamics: study of how energy is transferred (passed along) or transformed (changed into a different kind of energy)

• System: matter under study• Universe: everything outside the system• Isolated system: system unable to exchange either energy or matter

with its surroundings; ex: thermos bottle• Open system: energy and matter can be exchanged between the

system and its surrounds

Laws of Thermodynamics

• First law: Energy can be transferred and transformed, but it cannot be created or destroyed; principle of conservation of energy

• Electric Company does not make energy; they convert it to a usable form• Plants are not actually energy producers, more accurate to call them energy

transformers.

• Second Law: Every energy transfer or transformation increases the entropy of the universe; for a process to be spontaneous, it must increase the entropy of the universe

What is Entropy?• Measure of disorder, or randomness• The more randomly arrange matter is, the greater its entropy• Although order can increase locally, the trend towards randomization of the

universe is unstoppable• As chemical energy in food (C6H12O6) is converted into kinetic energy

(movement) the release of CO2 + H2O + heat is causing the universe to become more disordered; localized order is increased at the expense of the universe becoming more disordered

• For a process to occur on its own it must increase the entropy of the universe; no energy is needed

• If a reaction results in a product that is more ordered than the reactants it is going to require energy and will not take place on its own…endergonic or nonspontaneous

Free-Energy Change, ∆G

• The following is an equation that can be used to determine the free energy available in a chemical reaction:

∆G = ∆H – T∆S

• ∆G = change in free energy; energy available to do work• ∆H = change in system’s enthalpy (in biological systems = total energy)• T = absolute temperature in Kelvin (K)• ∆S = change in entropy; order of the system• If ∆G = -- then the reaction will be spontaneous and occur without energy; if ∆G

= + then the reaction will be nonspontaneous and will require energy

(a) Gravitational motion (b) Diffusion (c) Chemical reaction

• More free energy (higher G)• Less stable• Greater work capacity

In a spontaneous change

• The free energy of the system decreases (∆G < 0)

• The system becomes more stable

• The released free energy can be harnessed to do work

• Less free energy (lower G)• More stable• Less work capacity

• Less free energy (lower G)• More stable• Less work capacity

• More free energy (higher G)• Less stable• Greater work capacity

In a spontaneous change• The free energy of the system decreases (∆G < 0)• The system becomes more stable• The released free energy can be harnessed to do work

• ∆G can be negative only when the process involves a loss of free energy during the change from initial state to final state

• Free energy is the measure of a system’s instability – its tendency to change to a more stable state

• Unless something prevents matter, it wants to move to a more stable state

• Free energy (ability to do work) increases when a reaction is somehow pushed away from equilibrium

• A process is spontaneous and can perform work only when it is moving towards equilibrium

Fig. 8-5b

Spontaneouschange

Spontaneouschange

Spontaneouschange

(b) Diffusion (c) Chemical reaction(a) Gravitational motion

Digestion Time/Application1. Assume temperature and enthalpy do not change…based

on the equation for free energy change, how would entropy need to change in order for ∆G to be negative? Would entropy increase or decrease? If entropy increases, does that mean the reaction causes an increase in disorder or decrease in disorder?

2. Assume temperature and entropy do not change…based on the equation for free energy change, how would enthalpy need to change to cause ∆G to be negative? Would the reactants or products become more or less stable?

Digestion Debrieft

1. Increase in entropy (∆S) would lead to a negative ∆G reaction would INCREASE in disorder

2. Decrease in enthalpy (∆H) would lead to a negative ∆G the products would be more stable than the reactants; the reaction is exergonic (releasing energy)

Three main kinds of work

• Chemical work: pushing of endergonic reactions, which would not occur spontaneously, such as the synthesis of polymers from monomers

• Transport work: pumping of substances across membranes against the direction of spontaneous movement

• Mechanical work: movement (contraction of muscles, beating of cilia, movement of chromosomes during cell division)

Energy Coupling

• Energy coupling: the use of an exergonic process to dive an endergonic reaction

• ATP is responsible for most energy coupling in cells• Structure of ATP (adenosine triphosphate):

• Essential the RNA adenine nucleotide with two additional phosphate groups

3 Phosphate groups Ribose

Adenine

Is ∆G negative or positive when ATP becomes ADP?

Inorganic phosphate

Energy

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

P P

P P P

P ++

H2O

i

- Which molecule is more stable?

- Is there more of less disorder in ATP or ADP?

- Is this reaction endergonic or exergonic?

- Is this reaction spontaneous or non spontaneous?

(b) Coupled with ATP hydrolysis, an exergonic reaction

Ammonia displacesthe phosphate group,forming glutamine.

(a) Endergonic reaction

(c) Overall free-energy change

PP

GluNH3

NH2

Glu i

GluADP+

PATP+

+

Glu

ATP phosphorylatesglutamic acid,making the aminoacid less stable.

GluNH3

NH2

Glu+

Glutamicacid

GlutamineAmmonia

∆G = +3.4 kcal/mol

+2

1

How ATP drives chemical work

• ATP drives endergonic reactions by phosphorylation (transferring a phosphate group to some other molecule)

• The recipient molecule is now phosphorylated energy rich and unstable

• The combined rxns are exergonic

(b) Mechanical work: ATP binds noncovalently to motor proteins, then is hydrolyzed

Membrane protein

P i

ADP+

P

Solute Solute transported

Pi

Vesicle Cytoskeletal track

Motor protein Protein moved

(a) Transport work: ATP phosphorylates transport proteins

ATP

ATP

How ATP drives transport and mechanical work

• The phosphate group from the ATP binds the the protein and causes the shape of the protein to change

The Regeneration of ATP

• ATP is a renewable resource that is regenerated by addition of a phosphate group to adenosine diphosphate (ADP)

• ADP + P --> ATP• The energy to phosphorylate ADP comes from catabolic

reactions in the cell.• The chemical potential energy temporarily stored in ATP

drives most cellular work.

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The ATP cycle

PiADP +

Energy fromcatabolism (exergonic,energy-releasingprocesses)

Energy for cellularwork (endergonic,energy-consumingprocesses)

+ H2OATP

How much total energy does an organisms need to stay alive?

• Metabolic rate: amount of energy an animal uses in a unit of time• Can be determined in several ways:

• Because nearly all of the chemical energy used in cellular respiration eventually appears as heat, metabolic rate can be measured by monitoring an animal’s rate of heat loss

• Amount of oxygen consumed or carbon dioxide produced • Record the rate of food consumption, the energy content of the food and chemical

energy lost in waste products

• Amount of energy is going to differ depending on size, shape, and type of thermoregulation (how an organisms stay warm), age, activity, nutrition, temperature

• Endotherm: internal• Ectotherm: external

Size and Metabolic Rate

• In general smaller organisms have a higher metabolic rate than larger animals; a mouse needs more energy per unit mass compared to an elephant. This does not mean the elephant eats less than the mouse…it means the elephant needs less energy for every square inch of body mass compared to the mouse

Activity and Metabolic Rate

• Increased activity = increased need for energy• Decreased activity = decreased need for energy• What happens when you have an excess supply of energy?

• Storage – what does this mean???

• What happens when you have a deficient of energy?• Organism dies• What impact does this have on the population? Ecosystem?

• Leads to disruptions in ecosystems

• To conserve on energy during times of stress some organisms go into a Torpor or Hibernation state (long term torpor)