LEQ: What is the role of ATP in cellular activities?Cellular EnergyPages 72 to 75

EnergyWhat is energy?

◦The capacity to do workWhat is Kinetic energy?

◦Energy of motion◦Heat (thermal energy) is kinetic energy given

off due the the movement of moleculesWhat is Potential energy?

◦Stored energy that an object possess as a result of its location or structure

◦Chemical energy is 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.

ThermodynamicsWhat is thermodynamics?

◦The study of energy transformation

◦Organisms are open systems

◦In an open system, energy and matter can be transferred between the system and its environment

The First Law of ThermodynamicsAccording to the first law of

thermodynamics, the energy of the universe is constant: – Energy can be transferred and

transformed, but it cannot be created or destroyed

The first law is also called the principle of conservation of energy

The Second Law of Thermodynamics

During every energy transfer or transformation, some energy is unusable, and is often lost as heat

According to the second law of thermodynamics: – Every energy transfer or

transformation increases the entropy (disorder) of the universe

(a) First law of thermodynamics (b) Second law of thermodynamics

Chemicalenergy

Heat CO2

H2O+

Biological Order and DisorderLiving things are ordered,

decreasing entropy - this requires an input of energy, increasing entropy….◦Building macromolecules

(dehydration synthesis) decreases entropy by organizing atoms into molecules, molecules into cells, etc…

◦In order to build / maintain organization requires an input of energy which increases entropy

Chemical ReactionsEndergonic Reactions

◦“Energy In”◦Require a net input of energy◦Rich in potential energy◦Photosynthesis – takes in energy to

produce sugar; energy stored in bonds

Fig. 8-6b

Energy

(b) Endergonic reaction: energy required

Progress of the reaction

Free

ene

rgy

Products

Amount ofenergyrequired(∆G > 0)

Reactants

Chemical ReactionsExergonic Reactions

◦“Energy Out”◦Chemical reactions that release

energy◦Cellular respiration – breaking bonds

of sugar to release energy

Fig. 8-6a

Energy

(a) Exergonic reaction: energy released

Progress of the reaction

Free

ene

rgy

Products

Amount ofenergyreleased(∆G < 0)

Reactants

Chemical ReactionsCellular Metabolism

◦Sum of all exergonic and endergonic reactions in a cell

◦Anabolic Pathways – consume energy to build complex molecules from simple ones (endergonic)

◦Catabolic Pathways – release energy by breaking down complex molecules into simple ones (exergonic)

Chemical ReactionsEnergy Coupling

◦The use of energy released from exergonic reactions to drive essential endergonic reactions

Adenosine Triphosphate

Phosphate groupsRibose

Adenine

Energy currency of the cellPowers nearly all cellular work

through energy coupling reactions

Fig. 8-9

Inorganic phosphate

Energy

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

P P

P P P

P ++

H2O

i

ATP – ADP Cycle

P iADP +

Energy fromcatabolism (exergonic,energy-releasingprocesses)

Energy for cellularwork (endergonic,energy-consumingprocesses)

ATP + H2O

Phosphorylation - adding a phosphate

Cells use ATP Three types of cellular work that

are powered by hydrolysis of ATP◦Cell Transport – Bringing materials

into cells◦Mechanical Work – muscle

contractions◦Chemical Work – macromolecule

synthesis

Fig. 8-11

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

Membrane protein

P i

ADP+

P

Solute Solute transported

P i

Vesicle Cytoskeletal track

Motor protein Protein moved

(a) Transport work: ATP phosphorylates transport proteins

ATP

ATP