Week 5 Homework Flashcards
Select all of the following terms / phrases that describe metabolism in living organisms.
I. energy transformation
II. inefficient
III. unregulated
IV. change in free energy
V. independent chemical reactions
I and IV
The ΔGo of a reaction quantifies the energy necessary for moving a reaction from the standard state to?
Equilibrium state
The difference between ΔGº’ and ΔGº is that ΔGº’ assumes the of the system is buffered similar to physiological conditions, unlike ΔGº.
pH
True or false? Both ΔG and ΔGº′ are equal to zero at equilibrium.
False
True or false? ΔG is a measure of the actual free energy change of a reaction in a cell and ΔGº′ is a measure of the free energy change under biochemical standard conditions
True
True or false? ΔG and ΔGº′ are both fixed values and do not change when the concentrations of product and/or reactant change.
False
What is the difference between ΔG and ΔGº′?
ΔG gives us a measure of free energy change under cellular conditions and ΔGº′ gives us a measure of free energy change under standard conditions
ΔG varies depending on the concentrations and ΔGº′ is a fixed value.
The terms Q and K refer to reaction components at non-equilibrium and equilibrium conditions, respectively. For a forward reaction to be favored in a living cell, which of the following statements describes the relationship between Q and K?
I. The value of K must be less than that of Q.
II. The value of Q must be less than that of K.
III. No conclusion can be drawn about Q and K for a favorable process.
IV. Cells are at equilibrium so none of the above statements is true.
II
In order for a reaction to proceed to the right (forward) then the concentration of products must be lower than they are at equilibrium, which makes Q less than K
If a given reaction is endergonic, which of the following alterations to the cellular conditions could make the ΔG for the reaction favorable?
I. maintaining a high starting-material (reactant) concentration
II. keeping a high product concentration
III. using the product immediately in the next step
I and III
For an unfavorable reaction, the free energy change is and the are favored to reach equilibrium.
Positive; reactants
True or false? When a reaction is at equilibrium, the concentrations of the products and reactants are equal.
False
True or false? When a reaction is at equilibrium, the biochemical reaction is reversible.
True
True or false? When a reaction is at equilibrium, the rates of the forward and reverse reactions are equal.
True
True or false? The reaction is at equilibrium, the Keq is equal to 1.
False
If the cellular conditions are such that Q = 2.2 x 10-5, then which pair of terms describe the chemical reaction under these conditions?
Reversible vs irreversible
Favorable vs not favorable
Reversible and not favorable
If a reaction is reversible and not favorable, what does this indicate about the relationship between Q and K?
Q>K
TRUE or FALSE: The equilibrium constant of a reaction is not related to the change in free energy of the reaction.
False
TRUE or FALSE: The equilibrium constant of a reaction can change if the concentration of reactants and products are changed.
False
Life is a(n) ________ process, such that it never comes to equilibrium.
Irreversible
True or false? The reaction rate is independent of ΔG.
True
True or false? If ΔG is negative, then the rate of the reaction will be slow.
False
True or false? If ΔG is negative, then the rate of the reaction will be fast.
False
True or false? If ΔG is positive, then the rate of the reaction will be fast.
False
A negative value for ΔG would indicate that…
free energy is available to do work and the process is thermodynamically favorable.
For any chemical reaction, what will happen to the rates of the forward and reverse reactions when an enzyme is added?
Both the forward and reverse rates of a reaction increase.
True or false? All enzymes are proteins.
False
True or false? Enzymes generally bind to one or a few substrates making them highly specific.
True
True or false? Enzymes make the ΔG of a reaction more negative and therefore, more favorable.
False
True or false? Enzymes are highly efficient, allowing a reaction to proceed in a biologically useful time frame.
True
An enzyme is when it loses its native conformation and its biological activity.
Denatured
An enzyme is considered a because it speeds up chemical reactions without being used up.
Catalyst
An enzyme is considered because of its ability to recognize the shape of a particular molecule.
Specific
A , such as a vitamin, binds to an enzyme and plays a role in catalysis.
Cofactor
When properly aligned, the enzyme and substrate form an enzyme-substrate (ES) .
Complex
A substrate binds to an enzyme at the , where the reaction occurs.
Active site
In a catalyzed reaction a reactant is often called a .
Substrate
True or false? The rate of the reaction will change when an enzyme catalyzes a chemical reaction.
True
True or false? The free energy of the transition state will change when an enzyme catalyzes a chemical reaction.
True
