Chapter 3 : The Energetics of Life

Irreversible processes follow which law?

le Chatlier's Principle

T/F: ΔG ̊' is much more negative than ΔG for ATP hydrolysis at standard biochemical conditions

False: The ΔG is much more negative than ΔG ̊' for ATP hydrolysis at standard biochemical conditions.

Since *living systems are not isolated* and we must not describe them such in terms of the 2nd law of thermodynamics, what must we utilize?

Gibbs free energy (G)

T/F: even if ΔG ̊ is positive, under proper concentrations the ΔG can still be negative!

True

Calorimetry

a way to measure heat in a closed system

delta G (knot) a) free energy is... b) process in terms of thermodynamics c) in biochemical terms

a) 0 b) reversible c) equilibrium

Homeostasis vs. Equilibrium a) ________________ is required to maintain homeostasis b) the importance of homeostasis c) how must the cells maintain their homeostasis with regard to equilibrium standards?

a) Energy b) serves as a system of control applied by living systems to ensure metabolic reactions do not get out of control. c) steady-state concentrations (homeostatic condition) are maintained far from equilibrium values.

First Law of Thermodynamics and enthalpy a) under what type of system does enthalpy usually occur within b) what are the simple terms of this law?

a) In a closed system, only energy is exchanged with the surroundings (as either work or heat). - energy is neither created nor destroyed, but rather it is conserved

E ̊ a) what does it represent? b) what does it describe? c) The greater the standard reduction potential, ....

a) Standard reduction potential b) describes the tendency of some species to GAIN electrons. c) the greater the tendency for a given electron carrier to become reduced

Keq (equilibrium constant) a) when is it used? b) *K>1* (which reaction is favored? c) *K<1*

a) Used when systems are at EQUILIBRIUM Products/ Reactants b) forward reaction is favored c) forward reaction is not favored

biochemical standard state a) the activity of H+ b) initial standard conc. of majority of aq. solutions/species

a) [H+]=10^-7 M b) 1 M

Entropy high/low states a) Entropy can decrease, but... b) in which manner of the states of matter does entropy increase?

a) at the expense of energy b) solids < liquids < gases

Enthalpy (H) and its conditions - desribe the system it is found in accordance - in what conditions must the sytem be in?

*heat exchanged* between the system and the surroundings when the systems is at *constant pressure* / *closed system* (which is the typical condition of living systems).

Mass action expression (Q) a) when is it used?

- Used when a reaction is NOT at equilibrium (MOST systems)

delta G (-) a) free energy is... b) process in terms of thermodynamics c) in biochemical terms

a) available to do work b) thermodynamically favorable c) exergonic

The reversible process is at equilibrium when: (provide an example)

-Its the LOWEST energy state of the system -*The forward and reverse rates of the process are EQUAL* EX: Ice melting at 0 degrees celsius

During calorimetry, the heat (q) delivered to the bath (which is at a constant P) is equal to ?

-delta (H) of the rxn

What are the 3 types of systems

1. closed 2. open 3. isolated

Systems are defined in terms of (4 things)

1. composition 2. temperature 3. pressure 4. volume

Provide a few examples of coupled reactions

1. pumping metabolites across membranes against a conc. gradient, 2. transmission nerve impulses 3. muscle contractions

The free energy change of a chemical reaction depends on (2 things)

1. the standard (total) free energy change (ΔG ̊), which uses the equilibrium state as a reference. 2. the (initial) concentrations (in M) of the reactants & products (described by "RT[ln Q]"). *ΔG = ΔG ̊ + RT ln(Q)*

Irreversible processes (provide example)

Are set up far from an equilibrium state and will proceed TOWARDS an equilibrium state *(can only go 1 way, forward direction)* EX: burning paper

The energy currency in cells is _______________ , found in its _________________________

ATP ; 3 phosphodiester bonds

From the standpoint of entropy, consider the following processes: water boiling, mixing cola and root beer sodas, and assembling a house of cards. Based on your understanding, which of the following statements is true? A) Water boiling is a favorable process, but mixing cola and root beer sodas and assembling a house of cards are not. B) Water boiling and mixing cola and root beer sodas are not favorable processes, but assembling a house of cards is. C) Water boiling and mixing cola and root beer sodas are favorable processes, but assembling a house of cards is not. D) All of the listed processes are favorable.

C) Water boiling and mixing cola and root beer sodas are favorable processes, but assembling a house of cards is not. Reasons: 1) house of cards - For assembling a house of cards, the final condition of the system is smaller than the initial condition of the system; hence the resulting change in *entropy is negative*. Therefore, the process is not a favorable one (non-spontaneous process). 2) Mixing of Sodas and Boiling of Water -The entropy of molecules increases with the changing of the physical states of matter from solid to gas due to internal degrees of freedom of motions. solids< liquids< gases Water boiling is a favorable process because water changes from liquid state to gaseous state. Mixing of cola and root beer sodas is the increase of the total number of molecules in the final system. So, the change in entropy is positive for the above processes.

Closed systems

Can exchange energy (e.g. heat or work) but not matter with surroundings.

Open Systems

Can exchange matter and energy with surroundings.

Isolated Systems

Can exchange neither matter nor energy with surroundings.

Reversible process

Is NEAR a state of equilibrium

Entropy (S)

Is a state function that measures the *degree of randomness* or disorder of a system a type of state function (path independent)

How do living systems allow for the driving of so called unfavorable reactions to proceed forward?

Living systems have cleverly "coupled" unfavorable process with favorable processes to drive the unfavorable process forward

Assuming constant pressure, rank these reactions from most energy released by the system to most energy absorbed by the system, based on the following descriptions: 1.Surroundings get colder and the system decreases in volume. 2. Surroundings get hotter and the system expands in volume. 3. Surroundings get hotter and the system decreases in volume. 4. Surroundings get hotter and the system does not change in volume.

Most energy released to most absorbed: 2, 4, 3, 1 Also: to expand the volume of your system requires more energy built up to be released. Remember: ΔE, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy.

When a system is at equilibrium what happens to the relationship of Gibbs Free energy (delta G) and mass action expression (Q) ?

Q = K delta G = 0 equilbrium is reached

What does it mean when homeostasis is maintained far from equilibrium (describe in terms of K, Q, and ΔG)

Q far from K; such that ΔG ≠ 0.

Delta H (change in enthalpy) is a __define the path, what type of function_

State Function, it is path independent, doesn't matter how it gets there

Hess' Law

Sum of the steps totals the whole -add reactions together

What is an important step of glycolysis?

The Isomerization of glucose-6-P to fructose-6-P

The second law of thermodynamics and entropy - what will happen to the entropy of this system knowing it's standards?

The entropy of an *isolated system* will tend to increase to a max value

Delta G (Gibbs Free Energy)

The portion of total energy change that is available to do useful work at constant T and P --> for living organism

effect of delta H, delta S, and T on delta G a) when inc. T b) when dec. T

a) delta H < T (delt. S), -delt (G) b) delta H > T (delt. S), -delt (G)

Standard state conditions (STP) a) define what type of processes it relates to and in which direction b) conditions for T and P c) what is the standard conc. for solutions?

a) many biochemical processes of living organisms would fail to react or proceed in the forward direction b) T = 298.15 K and P = 1 atm. c) 1 M

Standard free energy changes in oxidation-reduction reactions - what do the following represent? a) n b) F c) ΔE ̊'

a) number of electrons transferred b) Faraday's constant (96.5 kJ/mol V) c) difference in standard reduction potentials between the two redox couples (under biochemical standard conditions).

oxidation-reduction reactions a) the reductant is ________________ b) the oxidant is __________________

a) oxidized b) reduced

delta G (+) a) free energy is... b) process in terms of thermodynamics c) in biochemical terms

a) required to do work b) thermodynamically unfavorable c) endergonic

What determines the driving force for the reaction under non-standard conditions (i.e. cellular conditions)? a) ΔG b) ΔG ̊'

a) ΔG

Water, buffered solutions, and the *biochemical standard state* finding the formula (delta G for a reaction)

also : T = 298.15 K P= 1 atm

Define "Systems"

any part of the universe that we choose to study and everything else is the surroundings

What is the fate of the phosphate group that is removed when ATP is converted to ADP? a) It is broken down into one phosphorus and four oxygen atoms. b) It is acquired by a reactant in an endergonic reaction. c) It is acquired by a reactant in a spontaneous reaction. d) It is acquired by a reactant in an exergonic reaction. e) It is used to convert an ATP into an AQP.

b) It is acquired by a reactant in an endergonic reaction.

At the melting temperature of water, which of the following statements is true? a) The reaction is spontaneous because ΔH is greater than -TΔS. b) The value of TΔS must be greater than the ΔH component. c) The value of TΔS must equal the value of ΔH. d) There is not enough information to answer this question.

c) The value of TΔS must equal the value of ΔH. entropy of fusion: ΔS = ΔH/ T re-write for temperature: TΔS =ΔH

Living systems generally operate at what conditions?

constant temperature and pressure

A solution of 2M NaCl in water is separated from pure water by a semipermeable membrane. Which of the following is true? a) The crossing of NaCl is an endergonic process. b) Nothing will happen because the system is at ΔG = 0. c) Water will move from the 2M NaCl solution to the pure water compartment. d) NaCl will migrate (diffuse) across the membrane until there is an equal concentration on both sides.

d) NaCl will migrate (diffuse) across the membrane until there is an equal concentration on both sides.

The conversion of A to B is coupled to the conversion of C to D. Which statement most accurately describes this sequence? a) Both reactions are equally endergonic. b) The first reaction (A to B) must be more exergonic than the second reaction (C to D) is endergonic. c) The first reaction must be exergonic and the second must have a ΔG = 0. d) The second reaction (C to D) must be more exergonic than the first reaction (A to B) is endergonic.

d) The second reaction (C to D) must be more exergonic than the first reaction (A to B) is endergonic. Exergonic reactions: reactions that have a negative delta G, the reaction is spontaneous and thermodynamically favorable. The reactant have more free energy than the products and they occur without the addition of energy. Endergonic reaction Reactions with a positive delta G (>0) , reactions are non-spontaneous and unfavorable. The products have more free energy and require an input of energy. They cannot happen without the input of energy and must be coupled with exergonic reactions. A --> B should have a positive delta G (being endergonic) C --> D should have a negative delta G (being exergonic)

Based on the thermodynamic functions of enthalpy and entropy, can an unfavorable reaction that has a positive ΔG at RT be made favorable by increasing the reaction temperature? a) only if both ΔH and ΔS are negative b) No, an unfavorable reaction cannot be rendered favorable. c) yes, but only if ΔH is positive and ΔS is negative d) Yes, regardless of the sign of ΔH, if ΔS is positive, a reaction can be rendered favorable by increasing the temperature.

d) Yes, regardless of the sign of ΔH, if ΔS is positive, a *reaction can be rendered favorable by increasing the temperature.*

Under standard conditions, a given reaction is endergonic (i.e., DG >0). Which of the following can render this reaction favorable: using the product immediately in the next step, maintaining a high starting-material concentration, or keeping a high product concentration? a) keeping a high product concentration b) maintaining a high starting-material concentration c) using the product immediately in the next step d) using the product immediately in the next step and maintaining a high starting-material concentration

d) using the product immediately in the next step and maintaining a high starting-material concentration Reason: High product concentrations, according to La Chatelier's principle, will drive the reverse reaction.

The energy for an endergonic reaction comes from a(n) _____ reaction. exergonic anabolic synthesis glucose + glucose --> maltose ADP + P --> ATP

exergonic

Q < K delta G < 0 a) what reaction is favored b) is it spontaneous or not b) affect on heat and entropy; exergonic or endergonic?

forward reaction is favored spontaneous (negative delta G) *exergonic*: releases heat and increases entropy (favorable)

Q > K delta G > 0 a) what reaction is favored b) is it spontaneous or not b) affect on heat and entropy;exergonic or endergonic?

reverse reaction is favored; non-spontaneous (positive delta G) endergonic: absorbs heat and decreases entropy (unfav.)

During both equilibrium and homeostasis, what happens to the concentrations of reactants and products?

they stay constant

is hydrolysis of ATP to ADP favored?

yes, highly