Bio 1330: Energetics

test 2

What is free energy (Gibbs free energy)?

The energy available to do work in a system.

What does ∆G represent?

The change in free energy during a chemical reaction: free energy of products minus free energy of reactants.

What does a negative ∆G mean?

The reaction is exergonic, releases free energy, and is spontaneous in the forward direction.

What does a positive ∆G mean?

The reaction is endergonic, requires a net input of free energy, and is nonspontaneous in the forward direction.

What is an exergonic reaction?

A reaction that releases free energy and has a negative ∆G.

What is an endergonic reaction?

A reaction that requires a net input of free energy and has a positive ∆G.

How do the free energy levels of reactants and products compare in an exergonic reaction?

Reactants have more free energy than products.

How do the free energy levels of reactants and products compare in an endergonic reaction?

Products have more free energy than reactants.

What is a spontaneous reaction?

A reaction that can occur without a net input of free energy; it does not necessarily occur quickly.

What is an anabolic pathway?

A pathway that builds complex molecules from simpler ones and requires energy; generally endergonic.

What is a catabolic pathway?

A pathway that breaks complex molecules into simpler ones and releases energy; generally exergonic.

What is the difference between anabolic and catabolic pathways?

Anabolic pathways build molecules and require energy; catabolic pathways break molecules down and release energy.

What is ATP, and what is its main function?

Adenosine triphosphate; it supplies usable energy for cellular work.

What are the three components of ATP?

Adenine, ribose, and three phosphate groups.

What is the difference between ATP and ADP?

ATP has three phosphate groups; ADP has two.

What is phosphorylation?

Adding a phosphate group to a molecule, often by transferring one from ATP.

How can phosphorylation change a protein's function?

It can change the protein's shape (conformation), affecting its activity or movement.

What is energetic coupling?

Linking an energy-releasing reaction, such as ATP hydrolysis, to a reaction that requires energy.

How can ATP help a nonspontaneous reaction occur?

ATP hydrolysis is coupled to the reaction so that the combined process has a negative overall ∆G.

How do you calculate the overall ∆G of coupled reactions?

Add the ∆G values of the individual reactions.

If one reaction has ∆G = +8 and another has ∆G = −12, what is the overall ∆G?

−4; the coupled process is exergonic and spontaneous in the forward direction.

What is the role of enzymes in metabolic pathways?

Enzymes catalyze individual reaction steps by lowering activation energy and speeding up reactions.

Do enzymes change a reaction's overall ∆G?

No. Enzymes lower activation energy but do not change the overall ∆G.

What is the relationship between glucose breakdown and ATP production?

Catabolic reactions break down glucose and release energy that cells capture to produce ATP.

What are NADH and NADPH?

Energy-related electron carriers that transfer reducing power and help support cellular processes.

What is entropy?

A measure of disorder or the number of possible arrangements in a system.

What changes generally favor a spontaneous reaction?

An increase in entropy and/or a decrease in energy, resulting in a negative overall ∆G.

What happens at chemical equilibrium?

The forward and reverse reaction rates are equal, so there is no net change; ∆G is zero under equilibrium conditions.

What are the three forms of energy emphasized in the reading?

Electrical energy, thermal energy, and potential energy.

What happens to ATP production and muscle relaxation after death?

ATP production stops, ATP is depleted, and muscles can become stiff because ATP is needed for normal muscle relaxation.