Bioenergetics

Question 1

A reaction is favorable when…

Answer 1

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

Question 2

A reaction is unfavorable when…

Answer 2

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

Question 3

If a reaction is at equilibrium…

Answer 3

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

Question 4

Delta G prime

Answer 4

Standard free-energy change at pH 7

Question 5

A simple way to determine delta G prime is…

Answer 5

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

Question 6

What can be done to make a reaction favorable?

Answer 6

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

Question 7

ATP

Answer 7

Cellular currency for energy. Has a high potential energy.

Question 8

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

Answer 8

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

Question 9

Formation of ADP

Answer 9

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

Question 10

How does ATP drive endergonic reactions?

Answer 10

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

Question 11

How do endergonic reactions needed for life occur in cells?

Answer 11

They occur in conjunction with an exergonic reaction involving ATP.

Question 12

How is ATP formation driven?

Answer 12

Reduction-oxidation reactions (Redox).

Question 13

When an atom or molecule loses an electron

Answer 13

It is oxidized. An H is removed

Question 14

When an atom or molecule gains an electron

Answer 14

It is reduced. An H atom is gained.

Question 15

What happens during a redox reaction?

Answer 15

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

Question 16

The more reduced a carbon atom is…

Answer 16

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

Question 17

Why do carbohydrates have more energy than CO2?

Answer 17

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.

Question 18

Why do fatty acids hold the most energy?

Answer 18

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

Question 19

Where is potential energy stored?

Answer 19

In the bonds of molecules.

Question 20

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

Answer 20

The terminal electron acceptor.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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