CH 1.3: Physical Foundations

Why do concentrations of molecules such as hemoglobin and glucose stay constant?

Rate of synthesis or intake = Rate of breakdown, consumption, or conversion

What is a system?

All the constituent reactants and products, the solvent that contains them, and the immediate atmosphere

What is the a universe?

The system and its surroundings

What is an isolated system?

System exchanges neither energy or matter with its surroundings

What is a closed system?

System exchanges energy but not matter with its surroundings

What is an open system?

System exchanges both energy and matter with its surroundings

What type of system are living organisms?

Open

How do organisms get energy?

• Take up chemical fuels from the environment and oxidizes them

• Absorbs energy from sunlight

What is the first law of thermodynamics?

Conservation of energy

In any physical or chemical change, the total amount of energy in the universe remains constant, although the form of the energy may change

What energy can cells interconvert?

• Chemical

• Electromagnetic

• Mechanical

• Osmotic

When a cell doesn’t have enough energy, what happens?

Goes from steady state towards equilibrium with its surroundings, causing the cell to decay

What are oxidation-reduction reactions?

One reactant is oxidized as another is reduced

What does it mean to be oxidized?

Loses electrons

What does it mean to be reduced?

Gains electrons

What is the second law of thermodynamics?

Randomness in the universe is constantly increasing.

What is entropy (s)?

Randomness or disorder of components of a chemical system

What is G?

Gibbs free energy

What is enthalpy (H)?

The heat of a system

What does it mean if delta H is negative?

Releases heat/ exothermic

What does it mean if delta H is positive?

Absorbs heat/ endothermic

What does it mean if delta S is positive?

Randomness increases

What does it mean if delta S is negative?

Randomness decreases

What is the Gibbs free energy equation?

Delta G = Delta H - (T)*(Delta S)

What does it mean if Delta G is negative?

Energy is released

What does endergonic mean?

Requiring energy

What does exergonic mean?

Releasing energy

What Delta G is thermodynamically favorable?

Delta G is negative

What does delta G mean?

Free energy change

What are bioenergetics?

Study of energy transformations in living systems

In closed systems, chemical reactions occur until what?

Equilibrium

What is equilibrium?

The rate of product formation is equal to the rate of reactant formation

In exergonic reactions, is there available energy to do work?

Yes

If the reaction is aA + bB → cC + dD, what does Keq equal?

Keq = [C]^c [D]^d / [A]^a [B]^b

What does it mean if Keq » 1?

Reaction proceeds until reactants are completely converted to products

What does Delta G note mean?

Standard free energy change

What does Delta G equal in terms of Delta G not?

ΔG = ΔG° + RT ln ([Initial Concentration of Products]^p / [Initial Concentration of Reactants]^r )

At equilibrium, ΔG is?

Zero

What does delta G not equal in terms of Keq?

ΔG° = -RT ln (Keq)

If Keq »1, then ΔG° is?

Large and negative

If Keq « 1, then ΔG° is?

Large and positive

What is kinetics?

The study of reaction rates

What is thermodynamics?

The study of how energy (heat) transforms and transfers during chemical reactions and physical transformations

Why is ATP breakdown exergonic?

All living cells maintain a concentration of ATP far above its equilibrium concentration

Why does ATP breakdown drive many endergonic processes?

The net reaction will be exergonic, which is favorable

Why is the transfer of a phosphoryl group to another small molecule important?

It causes the conservation of the chemical potential that was originally in ATP, making the new reaction spontaneous

What does kinetically stable mean?

Uncatalyzed breakdown occurs slowly

What does an enzyme do?

Enhance rate of chemical reactions without being consumed in the process

What is an activation barrier?

The path from reactants to products has an energy barrier that needs to be surmounted for the reaction to proceed

What is a transition state?

Highest energy point where bonds are partially broken and formed

What is activation energy (ΔG‡)?

The difference in energy between reactant in its ground state and transition state

Why do enzymes lower the activation energy?

The binding of an enzyme to the transition state makes the transition state more stable, releasing energy (exergonic) which is favorable

Why is exergonic more stable?

When a reaction releases energy, the molecules are going from a higher energy to a lower energy meaning the products are more stable

Why does an enzyme-catalyzed reaction occur incredibly fast (x10¹²)?

The reactants have to bind to the enzyme in a stereospecific orientation. Since the reactants are held in a position that is favorable, there is an increase of probability of productive collisions between reactants

Why do enzymes lower activation energy selectively?

It’s due to the multiplicity, their specificity, and their susceptibility to regulation

What are pathways?

Enzyme-catalyzed reactions are functionally organized into sequences of consecutive reactions; product of one reaction becomes reactant of next reaction

What is catabolism?

Degrade organic nutrients into simple end products to extract chemical energy and convert into its most useful form

What are some crucial molecules that catabolism produces?

• ATP

• NADH

• NADPH

What is anabolism?

Convert smaller precursor molecules to longer, more complex molecules

What is metabolism?

Consist of catabolism and anabolism

What are the connecting links between catabolic and anabolic reactions?

• ATP, adenosine triphosphate

• CTP, cytidine triphosphate

• UTP, uridine triphosphate

• GTP, guanosine triphosphate

What is feedback inhibition?

Keeps production and utilization of each metabolic intermediate in balance