Bioenergetics Flashcards
What constitutes an exergonic reaction?
An exergonic reaction is a spontaneous reaction, therefore, the Gibbs free energy is negative as the reaction releases energy.
What constitutes an endergonic reaction?
An endergonic reaction is not spontaneous, therefore the Gibbs free energy is positive and the reaction takes in energy.
Under what conditions is a reaction neither endergonic nor exergonic?
If there is no change in Gibbs free energy then the reaction is neither endergonic or exergonic.
In other words, the change in Gibbs free energy is zero.
What is the Gibbs free energy equation?
βπΊ=βπ»βπβπ
The change in Gibbs free energy is equal to the change in enthalpy minus the temperature*change in entropy
What is entropy?
(S) is a quantitative expression for the randomness (disorder) in a system
How do you increase entropy?
When the products of a reaction are less complex AND more disordered than reactants.
How do you decrease entropy?
When the reactants are less complex and disordered than the products.
What is enthalpy?
(H) is the heat content of the reacting system. It reflects the number and kinds of chemical bonds win the reactants and products.
What is happening if enthalpy is increased?
When the reaction consumes heat the change in enthalpy is positive.
What is standard free energy?
Change in Gibbs free energy of a reaction when the conditions are βstandard.β You must include the concentrations.
How do you find standard free energy?
Standard free energy is equal to the negative R times the temperature in Kelvin times the equilibrium constant.
βπΊ^β²Β°=βπ π ln(Keq)
βπΊ^β²Β°=βπ π lnβ‘( [products at equilibrium]/[reactants at equilibrium] )
What reaction conditions are used to measure standard free energy?
Temperature at 25C aka 298K
Atmospheric Pressure at 1 atm
pH at 7
55.5M H2O
1 mM Mg2+
1M of substrates
1M of products
What is Gibbs free energy?
Gibbs free energy expresses the amount of energy capable of doing work at constant temperature and pressure.
What is standard temperature in celsius?
25
What is standard temperature in Kelvin?
298K
What is standard body temperature?
310K
What is the change in Gibbs free energy equation in relation to standard gibbs free energy?
βπΊ=βπΊβ²Β°+π π lnβ‘γ[π΅_ππππ ]/[π΄_ππππ ] γ
What is the change in Gibbs free energy equation in relation to standard gibbs free energy?
βπΊ=βπΊβ²Β°+π π lnβ‘γ[π΅_ππππ ]/[π΄_ππππ ] γ
If a reaction is moving forward is it exergonic or endergonic?
exergonic
How many ways are there for endergonic reactions to occur?
2
One way for an endergonic reaction to occur involves the coupling of the reaction to a strongly exergonic reaction with a shared intermediate. How many steps does this involve?
This is a two-step reaction.
What molecule is often used to help endergonic reactions to proceed?
ATP because it is highly exergonic. First the reactant reacts with ATP to create a reactant-phosphate complex and then reacts with the other reactant to form the products and free phosphorus.
When ATP is used to help an endergonic reaction to proceed, is that known as pushing or pulling the reaction?
Pushing
What is meant when saying an endergonic reaction is pulled?
The reaction is said to be pulled when the endergonic reaction is coupled with an exergonic reaction. The sum of both of these products is negative so it continues.
How do you find the the Keq of a net reaction for two sequential reactions?
Ka mulitplied by Kb = Keq
What molecule does ATP become when the first phosphate bond is cleaved?
ADP
What molecule does ADP become when the 2nd phosphate bond is cleaved?
AMP
What is the main source of chemical energy in most organisms?
Oxidation of reduced carbon
Do reduced carbons have more or less electrons than oxidized carbons?
Reduced carbons have less electrons. Typically have less oxygens too.
Will the oxidation of glucose or a fatty acid provide more chemical energy per carbon atom given they have the same number of carbons?
The oxidation of the carbon is the main source of energy in organisms. The fatty acid will provide more chemical energy because each carbon has more potential to be oxidized.
What is the symbol for Reduction Potential?
βπΈ
Name four types of redox reactions
- Direct transfer of electrons
- Transfer of hydrogens
- Transfers of an hydride anion (H-)
- Direct combination with oxygen
What type of agent (reducing/oxidizing) is the most reduced reactant?
Reducing
Redox reactions can be written as two half-reactions. In which direction are the half-reactions written?
They are written in the direction of reduction. The product is reduced.
Which way will electrons spontaneously flow based on the Reduction Potentials?
The electrons will spontaneously flow from the more negative reduction potential to the more positive reduction potential
How can you tell spontaneity from the ruction potential?
The larger/positive the number, the more likely the reaction will be spontaneous
How do you find the change in reduction potential?
βπΈ=πΈ_ππ₯ β πΈ_πππ
aka
βπΈ=πΈ_πππππππ‘ππβπΈ_πππππ
