lecture 9 - bioenergetics Flashcards by Sophie Bliss

isolated system

cannot exchange energy or matter with its surroundings

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closed system

can exchange energy in the form of heat or work

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open system

can exchange both energy and matter with its surroundings

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What is thermodynamics

concerned with the direction/thermodynamic feasibility of the processes

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What is kinetics

concerned with the rate of processes

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what are bioenergetics

how living systems make use of free energy

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What is a system?

matter at a given temp, pressure and volume. part of the universe under study

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what is the surroundings?

entire universe excluding the system

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what is a process?

any change that occurs in the system

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what is the difference between transfer of heat (q) and work done (w)?

transfer of heat (q) to or from system
work done (w) by the system on its surroundings or work done by the system

q = energy transfer by random motion 
w = energy transfer by organised motion

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what does all energy end up as in the end?

All energy will eventually end up as heat energy

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what is the first law of thermodynamics?

energy cannot be created or destroyed, only transported…

…implies that the reaction can occur in either direction

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what is a state function?

depends only on the current properties or state of the system, not how the system reached the state

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Reaction for the change in enthalpy

delta H = delta U + P * delta V

change in enthalpy = change in energy + pressure * change in Volume

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what is the second law of thermodynamics?

Any spontaneous process must cause the entropy of the universe to increase

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What is entropy?

Measures the degree of disorder or randomness of a system

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What factors are unchanging at equilibrium?

temperature and total energy are unchanging at equilibrium

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What is the equation for Gibbs free energy?And what are the units?NEED TO LEARN

Delta G = Delta H - T*Delta S

Delta g = KJ/mol
Delta H = KJ/mol
T = Kelvin
Delta S = J/mol

What is a perturbed system?

by adding more molecules or by changing temp, then the system is no longer at equilibrium. The macroscopic variables will respond to the changes until the system reaches a new equilibrium.

What happens when you differentiate Delta G ?

Get minimum and maximum points on a graph.

what happens at minimum points?

small fluctuations in the system parameters will increase G

What is the free energy change of reaction?

total free energy or reactants go to total free energy of products

Delta G > 0

Forward process is energetically unfavourable

Delta G = 0

system is at equilibrium, no further change

delta G < 0

forward process is energetically favourable

What is an exergonic reaction?

Energy is released by the surroundings

what is an endergonic reaction?

Energy is absorbed by the surroundings

How do you make a reaction proceed in the correct direction

- alter the concentrations - couple the reaction; couple a positive data G value to on that has a negative Delta G value. this would mean that Delta G could be < 0

What is the free energy and concentration equation? The alternative Delta G equation? NEED TO LEARN

Delta G^o + RTln ( products/ reactants)

What does the standard free energy change mean/ represent?

Denotes that reactants and products are all at 1M concentration, temperature at 298k and pressure at 1 atmosphere

What is the third Delta G equation? NEED TO LEARN

Delta G = - RTlnKeq

What is the relationship between Delta G ^o and Keq?

Inverse basically. Delta G <0 then Keq >1 delta G >0 then Keq<1

What properties of ATP make it the major energy currency of biochemical processes

1. relief of electrostatic repulsion when terminal phosphate bond is hydrolysed – there is very little tendency for ADP and Pi to re-join as negative charges repel; 2. inorganic phosphate (Pi) undergoes stabilisation as a resonance hybrid 3. greater degree of solvation of the products ADP and Pi relative to ATP, further stabilising products relative to reactants. 4. two reactant molecules form 3 product molecules – more ways to distribute translational and rotational energy among 3 molecules – makes positive contribution to entropy.

what are standard quantities in Biochemistry?

conditions of defined molecular state used as a reference for reporting free energy values

what is the normal coupling in a Metabolic pathway?

- Endergonic reaction to an exergonic reaction, create a more negative delta G

what is ATP and why is it used?

common intermediate in the mainstream of energy . Can convert glucose into glucose - 6 - phosphate, coupling ATP hydrolysis can allow the reaction to be thermodynamically favourable

The thermodynamics and kinetics regarding ATP

ATP is thermodynamically unstable- which mean it can happen spontaneously. However because is it kinetically stable , it means it is very slow. Therefore enzymes are needed to catalyse the hydrolysis of the reaction

How can phosphates be transferred?

cannily be transferred from high energy to low energy compounds

Where is ATP positioned in the thermodynamic scale?

In the middle of the phosphate components

What is the enthalpy of a system?

tells us how much heat and work was added/ removed

What does delta G ^ o represent?

Its a constant for a given reaction and tells up the equilibrium constant

What does Delta G represent?

Represents extra free energy change

What happens to Keq when Delta G ^o is large and negative

Keq is very large

What happens to Keq when Delta G^o is large and positive?

Keq is very small