Section C Flashcards
Which biological processes are driven by light?
Synthesis of cellular macromolecules/membranes/phospholipids/metabolites, cellular movements, active transport, electrical potential generation, heat
Is heat a form of energy?
No, it’s fucking not
What is specific heat capacity?
Energy required to raise 1g of water by 1 degree
How many Joules is in 1 calorie?
4.2J
What is specific latent heat?
Energy change in Joules required to convert 1kg of mass from solid to liquid phase
What is a calorimeter?
Insulated device to measure temperature change in specific reaction
What is Kleiber’s law?
P proportional to M^3/4 (P = metabolic rate, M=mass)
What is the equation for metabolic rate?
P=dE/dT (rate of energy conversion)
Define an open system
System may exchange energy and matter with surroundings
Define a closed system
System may exchange energy with surroundings but not matter
Define an isolated system
No exchange can occur in system
Define the surroundings
everything around the system that has physical contact with it - may or may not exchange heat or matter
What does a Maxwell-Boltzmann distribution curve show?
how energy is distributed, distribution is typically asymmetrical (weighted toward lower speeds)
What happens to Maxwell-Boltzmann curve as temperature increases?
Curve flattens and moves to right (more particles at higher speeds)
What is the equation using population states (very important!)?
Population state in En/Population state in E0 = e^-[(En-E0)/kT] (k=boltzmann constant)
What is the value and units of Boltzmann constant?
1.38 x 10^-23 J/K
What is temperature a measure of?
Average energy of a system
What increases with increasing temperature?
occupancy of higher energy levels increases with temperature
What increases with decreasing temperature?
proportion of lower energy states increases as temperature decreases
What is the Zeroth law of thermodynamics?
Energy flows between objects to equalise their temperatures, temperature shows which was energy will flow (like pressure)
What is an intensive property?
Intensive property is not additive & does not depend on amount of material, e.g. temperature
What is the first law of thermodynamics?
Internal energy U is the sum total of all possible energies in the system
Can the absolute value of U (internal energy) be determined?
No it fucking can’t
What is an extensive property?
Extensive property is additive - depends on the amount of material present e.g. energy
What is the equation for change in internal energy?
Delta U = q + w (q=heat transferred to system, w=work done on system)
What is a state function?
value is path independent (how you arrive) e.g. U, altitude
What normally represents a state function?
A capital letter
What is another name for ‘path independant’ on state functions?
Zero-Sum game
What is the definition of heat?
Transfer of energy due to a difference in temperature between system and surroundings -> change in random motion of atoms
What is the definition of work?
Transfer of energy to or from the system which results in coordinated/coherent motion of molecules in a system
What is the major difference between heat and work?
Heat involves a change in random motion of particles, work results in coordinated motion of particles
Is heat a form of energy?
NO it’s fucking not, it’s a transfer of energy
What is the change in any property taken in relation to?
the system, change in any property is with respect to the system
Is a reaction endothermic or exothermic if q > 0?
Endothermic, energy moving from surrounding to system
Is a reaction endothermic or exothermic if q
Exothermic, energy moving from system to surroundings
What is the case if w > 0?
Surroundings do work on system -> gains energy
What is the case if w
System does work on surroundings -> loses energy
What type of function is enthalpy?
State
What are 3 equations for work done (w)?
Work = -Fx = -pAx = -p.delta v
What is the equation for pressure?
P = F/A (F=force, A=area)
What is equal to change in enthalpy provided pressure and volume are kept constant?
q (heat transferred to system) = change in enthalpy -> delta H
Is a process endothermic/exothermic if delta H > 0?
endothermic, positive delta H is an endothermic reaction
Is it possible to calculate the absolute enthalpy of a substance?
No, only possible to calculate change in enthalpy (H) using thermochemical cycles
What conditions is H normally referenced to?
1mole (pure), 298.15K, 1bar (0.986932Atm)
What is the enthalpy of dissociation for H2?
436kJ/mol - endothermic process
What is the mean bond enthalpy?
average amount of energy needed to break a specific bond, measured over a wide range of molecules
What is the symbol for mean bond enthalpy?
Delta HB
What is Kirchoff’s law?
Describes variation of a reaction’s enthalpy with varying temperature (enthalpy increases with temperature)
On a plot of H vs T, how would you find heat capacity?
Heat capacity is the gradient of this plot, Cp = dH/dT
What is assumed about Cp (heat capacity)?
It remains constant over small temperature ranges
What is the equation using Cp to find enthalpy change?
Delta H2 = Delta H1 + Cp(T2-T1) (Delta H2 = enthalpy change at Temp. 2)
How do we calculate the enthalpy of protein folding?
Use isothermal calorimetry
How does isothermal calorimetry work?
2 chambers linked by feedback mechanism to keep temperature identical, acid/salt injected to unfold protein/ligand added to bind protein, measure temperature change/energy = enthalpy
What can the first law of thermodynamics not predict?
Direction of enthalpy change, only shows that work can be converted directly into heat
What function can show direction of enthalpy change?
Entropy
What is the equation for connecting entropy, heat and temperature?
Change in entropy = q/T (q=work, t=temp)
What type of reaction minimise entropy change?
Reversible reactions
What does adiabatic mean?
Completely isolated from world, ‘Isolated System’
What does this equation show? Delta S total = Delta S universe > 0
Equation shows that the entropy of the universe will always increase, if entropy change is positive then entropy increases = more random
How do we prove the equation showing entropy always increases?
Entropy change is always negative for hotter substances, whereas it is positive for colder substances, so entropy change hot
What is the second law of thermodynamics?
In any spontaneous process entropy increases, entropy of universe is increasing,
How do we work out efficiency from entropy?
using the fact that entropy change of hot + cold = 0, can then convert to q/T -> waste q/cold temp - transferred q/hot temp -> rearrange to get max power = transferred q x (1-(hot temp/cold temp))
What is the equation to work out max work (find efficiency)?
W max = transferred q x (1 - (hot temp/cold temp))
What is the equation for entropy of a phase change at constant T?
Change in entropy = change in enthalpy/temperature
What is the third law of thermodynamics?
For any perfect crystal, at T = 0K, entropy is 0
Which has the highest molar entropy: gas, liquid or solid?
Gas, greatest degrees of freedom
What does entropy measure?
The quality of energy -> how narrowly it is distributed
What is the equation for configurational entropy?
S proportional to lnW
What are the two most important equations for boltzmann/entropy?
S = k.lnW and S >/= q/T
What is the mole fraction and what is it’s symbol?
xA = moles of A / moles of everything in sample (no units) -> e.g. nA/(nA + nB)
What is molaLity?
Moles of solute / Mass of solvent -> moles/kg
Mole fraction is proportional to molality
HELL YEH FUCKIN RIGHT
What is the equation for entropy of mixing/expansion?
Delta S = n.R.ln(V2/V1) if V2 = volume of area which gas has expanded into
Is the change in enthalpy of mixing always positive or negative?
Always positive, so mixing is a spontaneous process
What does isothermal mean?
constant temperature
Why are biological systems isothermal?
They do not rely on temperature difference to do work, typically cell transfers energy out into surroundings but this means pV work cannot be done (pressure, volume)
What is the equation for Gibbs free energy?
Delta G = Delta H - T.Delta S
What is the definition of gibbs free energy?
Energy gathered from a change in the system which is available to do non-pV work
What type of reaction is occurring if Delta G is greater than 0?
Endergonic reaction
What biological reaction is spontaneous at all temperatures?
Conversion of glucose and oxygen into CO2 and H2O, forward reaction has a negative enthalpy change and positive entropy change (and ATP-> ADP + Pi)
What does the symbol mu stand for?
Chemical potential
What is chemical potential?
A measure of how Gibbs free energy changes per molecule of substance, how seep gradient is
What form of substance is mu at its highest?
Highest mu in a pure liquid
What is the equation for chemical potential (mu) of a gas?
mu = mu0 + RT.lnP (P=pressure)
What changes in the equation for chemical potential in solids and liquids?
lnP changes to lnX, where X is the number of moles
What is the equation for standard gibbs free energy?
Delta G0 = -RT.lnKeq (K=equilibrium constant)
Which direction would diffusion occur if chemical potential was higher in A than B?
particles would diffuse from A into B
What is the equation for osmotic pressure (pi)?
pi = cRT (c=solute concentration)
What is a very important example of an entropic effect?
Formation of lipid bilayers, clustering of non-polar molecules to form membranes
If a non-polar molecule is surrounded by water, is it an endothermic or exothermic process?
Endothermic process, due to polar head group, so enthalpy change is positive, formation of bilayers is favourable due to an overall positive entropy change due to the release of a lot of organised solvent
