Bioenergetics

Question 1

entropy

Answer 1

(S)

The measure of microscopic disorder of a system.

Question 2

enthalphy

Answer 2

(H)

the total energy of a thermodynamic system; ΔH is the heat generated at constant pressure

Question 3

free energy

Answer 3

(G)

energy of a reaction that can be used to do work (negative ΔG) or the energy required to drive a reaction (positive ΔG)

Question 4

high energy compounds

Answer 4

compounds with large negative free energies of hydrolysis (compounds that release a large amount of energy upon hydrolysis)

Question 5

first law of thermodynamics

Answer 5

energy can neither be created nor destroyed, E of the universe is constant

Question 6

second law of thermodynamics

Answer 6

spontaneous reactions occur in directions that will increase the overall disorder of the universe. So, the entropy of the universe is always INCREASING (ΔS>0)

Question 7

What are the two main categories of energy?

Answer 7

kinetic energy and potential energy

Question 8

What is kinetic energy?

Answer 8

energy in motion

Question 9

What is potential energy?

Answer 9

stored energy

Question 10

Examples of potential energy

Answer 10

chemical bonds
concentration gradients
electric gradients
redox pairs

Question 11

What has greater reduction potential and thus more energy, lipids or carbs?

Answer 11

Lipids (6 bonding e to C)

[Carbs: 4 bonding e to C]

Question 12

Equation for calculating the free energy at NON-STANDARD conditions

Answer 12

ΔG=ΔG° + RTln[products/reactants]
R=1.987cal/mol K
T=temp in K
ΔG° = free energy in standard state (298 K, 7pH, 1 atm, 1M reactants in H2O)

Question 13

Equation for free energy at EQUILIBRIUM

Answer 13

ΔG°= -RTlnKeq=2.3RTlogKeq

When ΔG = 0 (free energy at equilibrium

Question 14

When Keq is <1, ΔG° is _____

Answer 14

positive

Question 15

When Keq is >1, ΔG° is _____

Answer 15

negative

Question 16

When Keq = 1, ΔG° is _____

Answer 16

zero

Question 17

Calculate Keq (at equilibrium)

Answer 17

Keq=kf/kr= [C][D]/[A][B] (when A+B–>C+D)

Question 18

Calculate ΔG (equation)

Answer 18

ΔG= ΔH-TΔS
H: change in enthalpy
S: change in entropy
T: temp

Question 19

For ΔG, what is spontaneous, what is nonspontaneous?

Answer 19

ΔG is negative for spontaneous reactions
ΔG is positive for nonspontaneous reactions
{spont doesn’t tell you rate!}

Question 20

Equation for conversion b/t free energy and redox potential.

Answer 20

ΔG=-nFΔE
*remember negative sign
F=96,500 joules/volt mol
n= number of electrons transferred
ΔE=reduction potential in volts
STANDARD CONDITIONS

Question 21

What is ΔE? more positive? more negative?

Answer 21

Measure of atom/molec’s readiness to accept electrons.
more positive? more likely to accept electrons (high reduction potential, OXIDIZING agent)
more negative? less likely to accept electrons; low reduction potential (REDUCING agent)

Question 22

Electrons flow from ____ to _____ reduction potentials.

Answer 22

Low to high reduction potentials.
[Move from compounds with low E, to high E (oxidized reactants), and RELEASE energy]
E=reduction potential in volts

Question 23

Standard free energy changes for a reaction are______, so reactions with _____ and _____ free energy changes can be coupled.

Answer 23

additive
positive and negative
[Nonspontaneous reactions may be coupled with highly spont. rxn with a common intermediate to drive the nonspont. reaction FORWARD.]

Question 24

Ex. of coupling reaction

Answer 24

ATP is often coupled with unfavorable rxns.

Question 25

High energy compounds

Answer 25

Compounds whose bonds are hydrolyzed w/ the release of large amounts of energy (ΔG<t mean high bond energy, just means there are large differences in STABILITY of the products and reactants of hydrolysis of high energy compounds)

Question 26

Examples of high energy bonds:

Answer 26

phophoanhydride bonds in ATP (beta and gamma are higher energy than alpha)
Thioester bond (C-S-CO-C in acetyl CoA compound)
Phophoenolpyruvate bond (C-O-P)
Phosphocreatine bond (P-N)

Question 27

Way to harvest energy for ATP production?

Answer 27

oxidation of glucose