Understanding Coupled Reactions

The video tutorial explains the concept of coupled reactions, where a thermodynamically favorable reaction is used to drive an unfavorable one. It provides hypothetical examples to illustrate how reactions with different free energy changes can be coupled to achieve desired products. A practical example of extracting copper from copper(I) sulfide is discussed, showing how coupling with a favorable reaction makes the process feasible. The tutorial also covers the importance of coupled reactions in biochemistry, particularly in protein synthesis, where ATP hydrolysis drives the formation of dipeptides.

What is the role of a thermodynamically favorable reaction in a coupled reaction system?

• It decreases the pressure of the system.

• It increases the temperature of the system.

• It drives the unfavorable reaction forward.

• It stops the unfavorable reaction.

In the second hypothetical reaction, what happens to the equilibrium constant when the reaction is thermodynamically favorable?

• It becomes less than one.

• It remains unchanged.

• It becomes greater than one.

• It becomes zero.

How does coupling reactions affect the equilibrium of the first reaction?

• It shifts the equilibrium to the left.

• It shifts the equilibrium to the right.

• It has no effect on the equilibrium.

• It stops the reaction completely.

What is the overall change in free energy when two reactions are coupled?

• It is always positive.

• It is always zero.

• It is less than zero.

• It is greater than zero.

In the practical example, what is the role of sulfur in the coupled reaction?

• It is a common intermediate.

• It is a product of the reaction.

• It is an inhibitor.

• It acts as a catalyst.

What is the result of coupling the copper extraction reaction with the conversion of sulfur to sulfur dioxide?

• The reaction produces less copper.

• The reaction becomes thermodynamically favorable.

• The reaction becomes thermodynamically unfavorable.

• The reaction stops completely.

In biochemistry, what molecule is used to drive the formation of dipeptides?

• ATP

• Glucose

• FADH2

• NADH

What is the free energy change for the hydrolysis of ATP?

• Positive 29 kJ/mol

• Zero

• Positive 31 kJ/mol

• Negative 31 kJ/mol

Why is the formation of dipeptides considered thermodynamically unfavorable?

• It releases energy.

• It occurs spontaneously.

• It requires a high temperature.

• It has a positive change in free energy.

What happens to water in the coupled reaction of dipeptide formation?

• It is produced.

• It acts as a catalyst.

• It is consumed.

• It cancels out.