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Anabolic. Catabolic. Bioenergetics (Overview). Metabolism (Overview). Metabolism = Catabolism + Anabolism. Catabolic reactions are energy yielding. They are involved in the breakdown of more-complex molecules into simpler ones. Anabolic reactions are energy requiring.

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metabolism overview
Metabolism (Overview)

Metabolism = Catabolism + Anabolism

Catabolic reactions are energy yielding

They are involved in the breakdown of more-complex molecules into simpler ones

Anabolic reactions are energy requiring

They are involved in the building up of simpler molecules into more-complex ones

energy coupling in metabolism

Catabolic reaction

Anabolic reaction

Energy Coupling in Metabolism

Catabolic Reactions provide the energy that drives Anabolic Reactions forward

organisms are energy transducers

First Law of Thermodynamics:

Organisms are Energy Transducers

Energy can be neither created nor destroyed

Therefore, energy “generated” in any system is energy that has been transformed from one state to another (e.g., chemically stored energy transformed to heat)

Second Law of Thermodynamics:

Efficiencies of energy transformation never equal 100%

Therefore, all processes loseenergy, typically as heat, and are not reversible unless the system is open & the lost energy is resupplied from the environment

Conversion to heat is the ultimate fate of chemical energy

organisms are energy transducers6
Organisms are Energy Transducers

Organisms take in energy & transduce it to new forms (1st law)

As energy transducers organisms are <100% efficient (2nd law)

Organisms employ this energy to:

  • Grow
  • Protect Themselves
  • Repair Themselves
  • Compete with other Organisms
  • Make new Organisms (I.e., babies)

In the process, organisms generate waste chemicals & heat

Organisms create local regions of order at the expense of the total energy found in the Universe!!! We are Energy Parasites!

energy a reminder

Gravity (center Earth)

Waste Heat

(once reaches


Potential Energy

Energy (a reminder)


Kinetic Energy

free energy spontaneity9

Source of Energy

Spontaneous Reaction

Non-spontaneous Reaction

Free Energy & Spontaneity

Rather than lighting bulbs, in most biological systems incoming energy is either stored or is used to produce ATP

exergonic reaction spontaneous
Exergonic Reaction (Spontaneous)
  • Decrease inGibbs free energy (-G)
  • Increase in stability


  • Spontaneous (gives off net energy upon going forward)
  • Downhill (toward center of gravity well, e.g., of Earth)
  • Movement towards equilibrium
  • Coupled to ATP production (ADP phosphorylation)
  • Catabolism

Endergonic Rxn (Non-Spontaneous)

  • Increase inGibbs free energy (+G)
  • Decrease in stability


  • Not Spontaneous (requires net input of energy to go forward)
  • Uphill (away from center of gravity well, e.g., of Earth)
  • Movement away from equilibrium
  • Coupled to ATP utilization (ATP dephosphorylation)
  • Anabolism
low i e body temperature stability
Low- (i.e., body-) Temperature Stability

To be unstable, something must have the potential to change into something else, typically something that possesses less free energy

To be unstable, releasing something’s ability to change into something else must also be relatively easy (i.e., little input energy)

Why don't energy-rich molecules, e.g., glucose,

spontaneously degrade into CO2 and Water?

Therefore, Stability = already low free energy

Alternatively, Stability = high activation energy

Things, therefore, can be high in free energy but still quite stable, e.g., glucose

chemical reaction
Chemical Reaction

Without Catalysts, Transition States are Achieved

via an input of Heat, i.e., Higher Temperatures

Activation Energy 


Energy 

a.k.a., Substrate

if enzyme catalyzed

chemical reaction18
Chemical Reaction

Note no change in degree of spontaneity, i.e., in G

catalyzed reaction
Catalyzed Reaction

At a given temperature catalyzed Rxns can run faster because less energy is required to achieve the transition state

induced fit active site
Induced Fit (Active Site)

The Catalysis associated with Enzymes occurs within small regions on (or within) proteins called Active Sites

Induced Fit not only allows the enzyme to bind the substrate(s), but also provides a subtle application of energy (e.g., “bending” chemical bonds) that causes the substrate(s) to destabilize into the transition state

enzyme catalytic cycle
Enzyme Catalytic Cycle
  • Input of Activation
  • Energy
mechanisms of catalysis
Mechanisms of Catalysis

(1) Active sites can hold two or more substrates in proper orientations so that new bonds between substrates can form

(2) Active sites can stress the substrate into the transition state

(3) Active sites can maintain conducive physical environments (e.g., pH)

(4) Active sites can participate directly in the reaction (e.g., forming transient covalent bonds with substrates)

(5) Active sites can carry out a sequence of manipulations in a defined temporal order (e.g., step A  step B  step C)

mechanisms of catalysis25


Mechanisms of Catalysis

Metal Ion or =

Organic Molecule

= Organic


enzyme saturation



Enzyme Saturation

Enzyme Activity at Saturation is a function of Enzyme Turnover Rate

modification of enzyme activity
Modification of Enzyme Activity

Even at Saturation the rate of Enzymatic Reactions can be modified

multi subunit enzymes 1 2
Multi-Subunit Enzymes (1/2)

Recall that a Multi-Subunit Enzyme is a catalytic Protein that consists of more than one Polypeptide

This is a description of Allosteric Regulation (Inhibition)

multisubunit enzymes 2 2

This is Cooperativity

Multisubunit Enzymes (2/2)

This also is a form of Allosteric Regulation (activation)

enzyme localization
Enzyme Localization

Organization of Electron Transport Chain of Cellular Respiration: Substrate  Enzyme  Product  Enzyme chains are co-localized

first exam next wednesday
First Exam Next Wednesday

The first exam is scheduled for next Wednesday

This exam will cover chapters 2 through 6 (unit 1)

Expect ~same # questions per class met

That’s 7 classes x (3 to 5 questions/class) = 25 to 35 questions

Study over the weekend (perhaps already having started?)

Tuesday will be a recitation—bring questions!!!!

The exam will start as soon as we can get in the room

It’ll be limited in length by a need to get people to next classes

first exam next wednesday37
First Exam Next Wednesday

Let’s try to avoid the scholastic equivalent of this!