Thermodynamics

Question 1

coupling reactions

Answer 1

couple energetically unfavourable reaction with favourable
free energy changes are additive

Question 2

isolated system

Answer 2

cannot exchange matter or energy with its surroundings

Question 3

closed system

Answer 3

can exchange energy but not matter with its surroundings by heat or work

Question 4

open system

Answer 4

can exchange both matter and energy with surroundings
all living systems

Question 5

1st law thermodynamics

Answer 5

energy cannot be created or destroyed
state function

Question 6

state function

Answer 6

property that is independent of the history of the system
energy change is independent of pathway taken. depends only on initial and final states of the system

Question 7

enthalpy change

Answer 7

heat energy change at a constant pressure
state function
change in internal energy + volume

Question 8

2nd law thermodynamics

Answer 8

the combined entropy of system and surroundings must increase in any spontaneous process

Question 9

entropy

Answer 9

state function
measures degree of disorder of a system

Question 10

properties of a system at equilibrium at a global scale

Answer 10

temperature, total energy, entropy all stable

Question 11

what happens when you perturb an equilibrium system

Answer 11

global properties relax to new equilibrium values

Question 12

gibbs free energy

Answer 12

state function incorporating both energy and entropy changes
energy available to do work

Question 13

what happens when a system is far from equilibrium

Answer 13

tends to move to equilibrium in an irreversible process

Question 14

what happens to a system in equilibrium

Answer 14

change in G=0
process is reversible
can be made to go in either direction by small changes in conditions

Question 15

why is maximum equilibrium unstable

Answer 15

gibbs free at a local maximum
small deviation to system will drive it away from equilibrium

Question 16

why is free energy an extensive property

Answer 16

it depends on the amount of material (moles) in the system

Question 17

endergonic process

Answer 17

delta G > 0
forward process energetically unfavourable
reverse spontaneous

Question 18

exergonic process

Answer 18

delta G < 0
forward process energetically favourable and occurs spontaneously

Question 19

how do organisms make a specific reaction proceed in the direction required

Answer 19

altering concentrations
coupling reactions

Question 20

entropy equation

Answer 20

S=klnW
k=boltzman constant, 1.38 x10^-23
W= number of microstates

Question 21

equation for gibbs free involving standard free energy change

Answer 21

delta G = delta G standard + RT ln [C]^c [D]^d / [A]^a [B]^b

Question 22

mass action ratio

Answer 22

[products] / [reactants] = Keq

Question 23

standard conditions

Answer 23

1M
298K
1atm

Question 24

delta G standard equation with Keq

Answer 24

delta G standard = -RT lnKeq

Question 25

if delta G standard is less than 0, what does this mean for Keq?

Answer 25

> 1

Question 26

if delta G standard = 0, what does this mean for Keq?

Answer 26

=1

Question 27

if delta G standard is greater than 0, what does this mean for Keq?

Answer 27

<1

Question 28

thermodynamic basis of metabolic pathways

Answer 28

coupling of an endergonic reaction to an exergonic reaction with a more negative delta G, exploits fact that free energies are additive

Question 29

properties of ATP that make it have negative delta G

Answer 29

relief of electrostatic repulsion when terminal phosphate bond hydrolysed so its hydrolysis is thermodynamically favoured.
ionisation of ADP releases protons
ATP is thermodynamically unstable but kinetically stable so has high activation energy to hydrolyse.