Metabolism Mayhem
What term describes all of the chemical reactions occurring in a cell or organism?
Metabolism
What term describes a reaction that releases free energy?
Exergonic
What molecule is commonly called the cell’s energy currency?
ATP
What biological catalyst speeds up chemical reactions?
An enzyme
What is the name of a regulatory binding site located away from the active site?
The allosteric site
Which law of thermodynamics explains why cells cannot create new energy from nothing?
The First Law of Thermodynamics
If ΔG is negative, is a reaction spontaneous or nonspontaneous? Is it exergonic or endergonic?
Spontaneous; Exergonic
What reaction uses water to break ATP into ADP and phosphate?
Hydrolysis
On a Gibbs free-energy graph, which feature changes when an enzyme is added: the reactant level, product level, or height of the activation-energy peak?
The height of the activation-energy peak
Why does low temperature usually decrease enzyme activity without permanently damaging the enzyme?
It slows molecular movement and collisions.
Which type of metabolism breaks larger molecules into smaller molecules? Does it release energy?
Catabolism; Yes
A reaction breaks one large carbohydrate into several smaller molecules. What generally happens to entropy?
Entropy increases
Would ATP hydrolysis be most useful for powering a spontaneous or nonspontaneous cellular process?
A nonspontaneous/endergonic process.
Two reactions have the same reactants and products, but one has a lower energy peak. Which one is more likely enzyme-catalyzed?
The one with the lower peak.
Why can very acidic pH reduce enzyme activity?
It changes amino acid charges and can alter the active site’s shape.
Why are catabolic and anabolic reactions often linked within metabolism?
Energy released from catabolic reactions can be used to support anabolic reactions.
Why does a positive ΔG indicate that a reaction will not proceed spontaneously by itself?
Because the products have more free energy than the reactants, so the reaction requires an energy input.
A cell needs to form a peptide bond, an endergonic process. Explain how ATP can help.
Energy released from ATP hydrolysis can be coupled to peptide bond formation.
Why can an enzyme make a reaction occur faster without changing whether the reaction is exergonic or endergonic?
It lowers activation energy but does not change the free-energy difference between reactants and products.
Why can very high temperature cause a more severe loss of enzyme activity than very low temperature?
High temperature can denature the enzyme and disrupt its structure, while low temperature mainly slows collisions.
A cell is simultaneously breaking down glucose and building a protein. Explain how these two processes represent opposite sides of metabolism.
Glucose breakdown is catabolic and releases usable energy, while protein synthesis is anabolic and requires energy.
A reaction forms a larger molecule from smaller molecules and has a positive ΔG. Predict its general effects on entropy and spontaneity.
Entropy generally decreases, and the reaction is nonspontaneous on its own.
A cell has plenty of ATP, but ATP hydrolysis is not properly coupled to an endergonic reaction. Would the presence of ATP alone guarantee that the reaction proceeds? Explain.
No. The ATP hydrolysis must be coupled to the reaction so its released energy can drive the process.
An endergonic reaction has a positive ΔG and a high activation energy. If an enzyme is added, which of those two properties changes and how?
Activation energy decreases; ΔG remains positive.
An enzyme is at favorable temperature, favorable pH, and has abundant substrate, but its activity suddenly decreases after a regulatory molecule binds away from the active site. What type of regulation is occurring, and what likely happened to the enzyme?
Allosteric inhibition; the inhibitor bound to the allosteric site and changed the enzyme’s conformation, reducing activity.