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Flashcards in Bioenergetics Deck (22)
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A reaction is favorable when...

Delta G is LESS than zero. It is called an exergonic spontaneous reaction, the reaction will move forward.


A reaction is unfavorable when...

Delta G is GREATER than zero. It is called an endergonic nonspontaneous reaction, the reaction will move backwards.


If a reaction is at equilibrium...

There is no net change in the amount of reactant or product, delta G is zero.


Delta G prime

Standard free-energy change at pH 7


A simple way to determine delta G prime is...

Measure the concentrations of reactants and products when the reaction has reached equilibrium


What can be done to make a reaction favorable?

An unfavorable reaction can be made favorable by coupling the reaction to the hydrolysis of an ATP molecule (ATP to ADP).



Cellular currency for energy. Has a high potential energy.


Why do the electrons in ATP have a high potential energy?

Because the four negative charges in its three phosphate groups repel each other.


Formation of ADP

The hydrolysis of the bond between the 2 outermost phosphate groups, highly exergonic.


How does ATP drive endergonic reactions?

Energy released during ATP hydrolysis is transferred to a substrate by phosphorylation. The substrate molecules then bind to a specific location in an enzyme.


How do endergonic reactions needed for life occur in cells?

They occur in conjunction with an exergonic reaction involving ATP.


How is ATP formation driven?

Reduction-oxidation reactions (Redox).


When an atom or molecule loses an electron

It is oxidized. An H is removed


When an atom or molecule gains an electron

It is reduced. An H atom is gained.


What happens during a redox reaction?

Electrons can be transferred completely or they can shift their position in covalent bonds.


The more reduced a carbon atom is...

The more free energy is released upon oxidation. The more negative the delta G prime value is.


Why do carbohydrates have more energy than CO2?

Electrons in C-O bonds are held more tightly and therefore have low potential energy. Electrons in C-H and C-C bonds have more equal sharing of electrons and therefore have a higher potential energy.


Why do fatty acids hold the most energy?

They have more C-C and C-H bonds.


Where is potential energy stored?

In the bonds of molecules.


In the electron transport chain, O2 is referred to as...

The terminal electron acceptor.


When the oxidation of NADH is coupled to the reduction of O2 (in the electron transport chain)...

A lot of energy is released than can be used to drive the synthesis of ATP.


The standard free energy change for a redox reaction is directly proportional to...

The difference in standard reduction potentials of the two half cells.