SQ's for quiz 6
Anabolism results in the production of molecules with high amounts of potential energy stored in their chemical bonds. How can the reactions of anabolism occur without violating the requirement that all reactions must result in a decrease in free energy?
A reaction that would otherwise be endergonic is combined with an exergonic reaction. The overall reaction than occurs in multiple steps, each of which involves an exergonic reaction. Energy from ATP is often used to help combine an exergonic reaction with a reaction that would otherwise be endergonic.
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.
Whenever energy is transformed, there is always an increase in the
Entropy of the universe
Many of the reactions that occur during metabolism are reversible. Given the laws of thermodynamics, how is that possible?
Even in the same solution, some of the molecules of a particular species may have more energy than others
Many of the reactions that occur during metabolism are reversible. Given the laws of thermodynamics, how is that possible?
Even in the same solution, some of the molecules of a particular species may have more energy than others.
Which of the following is a statement of the second law of thermodynamics?
Every energy transfer or transformation increases the entropy of the universe
Which of the following statements is FALSE?
Hydrolysis of ATP to form ADP and inorganic phosphate is a highly endergonic reaction
When chemical, transport or mechanical work is done by an organism, what happens to the heat generated?
It is lost to the environment.
Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
If I try to hit a hockey puck, but miss and hit the ice instead, isn't that a violation of the first law of thermodynamics because my stick is no longer moving and neither is the puck?
No, because the kinetic energy from the motion of my stick will have been transferred/transformed into increased heat energy in the ice.
You realize that, for a particular reaction to occur, the molecules participating in that reaction need to have a certain minimum free energy level to get over the activation energy barrier. After measuring the average free energy levels of the potential reactant molecules, you discover that their average free energy levels are a little below that required to surmount the activation barrier. Should you be surprised when you then realize that the reaction is occurring, even though it is only occurring at a relatively low rate?
No, you should not be surprised because you only measured the average free energy levels of the potential reactant molecules. Some of the molecules likely have more than the average amount of free energy, meaning that they have enough free energy to surmount the activation barrier.
Which of the following is TRUE for all endergonic reactions in open systems (e.g. a cell)?
The products have more free energy than the reactants
What is the difference, if any, between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?
There is no difference.
Which of the following statements concerning catabolic pathways is TRUE?
They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.
Chemical reactions
always decrease the amount of energy in the universe that is available to do work.
Which of the following is most similar in structure to ATP?
an RNA nucleotide
Which of the following is considered an open system?
an organism
Which term precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
Which of the following types of reactions would decrease the entropy of a cell?
dehydration reactions
Spontaneous reactions
do not require an energy input to occur
ATP is formed
during many catabolic reactions during hydrolysis of many biological polymers (e.g. carbohydrates, lipids and proteins) by many exergonic reactions
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
The amount of disorder or randomness is a system is represented by
entropy (S)
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.
exergonic; endergonic
the amount of energy in a system that is available to do work is represented by
free energy (G)
Which of the following best describes enthalpy (H)?
in biological systems, enthalpy is equivalent to total energy
Entropy
is a measure of disorder or randomness
Every energy transfer or transformation increases the entropy of the universe
is a statement of the second law of thermodynamics
Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell.
A consequence of the fact that Gibb's free energy must decrease in a spontaneous reaction is
that a given reaction may proceed spontaneously in both directions, due to the fact that different reactant and product molecules will have slightly different energies.
The hydrolysis of ATP: ATP + H2O → ADP + Pi is exergonic, with a ∆G of -7.3 kcal/mol under standard conditions. What is the source of the 7.3 kcal/mol released in this reaction?
the difference between the potential energy in the bonds of ATP and the water molecule, minus the potential energy in the bonds of ADP and Pi. In other words: (potential energy in bonds of ATP + potential energy in bonds of H2O) - (potential energy in bonds of ADP + potential energy in bonds of Pi) = 7.3 kcal/mol
The respiration (catabolism) of glucose is exergonic.C6H12O6 + 6 O2 → 6 CO2 + 6 H2OWhat is the source of the free energy released in this reaction?
the difference between the potential energy in the bonds of the glucose and oxygen molecules, minus the potential energy in the bonds of the carbon dioxide and water molecules. In other words: (potential energy in bonds of 1 glucose molecule + potential energy in bonds of 6 O2 molecules) - (potential energy in bonds of 6 CO2 molecules + potential energy in bonds of 6 H2O molecules) = positive number
"Conservation of energy" is another way of stating
the first law of thermodynamics
Which of the following statements about biological systems is FALSE?
the total energy in a biological system cannot increase or decrease
At zero degrees Kelvin, in theory,
you will be frozen entropy will reach a minimum value water will be frozen
The mathematical expression for the change in the free energy of a system is ∆G = ∆H - T∆S. Which of the following is (are) TRUE?
∆G is the change in free energy.
The mathematical expression for the change in the free energy of a system is ∆G = ∆H - T∆S. Which of the following is (are) TRUE?
∆H is the change in enthalpy.
The mathematical expression for the change in the free energy of a system is ∆G = ∆H - T∆S. Which of the following is (are) TRUE?
∆S is the change in entropy.
Which of the following is (are) TRUE for anabolic pathways?
They consume energy to build up polymers from monomers.
Living organisms don't violate the 2nd law of thermodynamics because:
They typically increase the entropy of their surroundings
Which of the following is an example of potential rather than kinetic energy?
a food molecule
Which of the following is considered an open system?
a plant cell with a strong cell wall a clam an animal cell
for the reaction depicted in the figure below, the activation energy barrier for converting C and D to A and B via the non-catalyzed reaction is represented by
arrow E
Which of the following most accurately describe kinetic and potential energy?
kinetic energy is due to movement and potential energy is energy that is stored in matter that is not due to movement
In an isolated system
neither energy nor matter can leave the system.
Are most chemical reactions at equilibrium in living cells?
no
What is the change in free energy of a system at chemical equilibrium?
no net change
Which of the following is TRUE for all exergonic reactions in open systems (e.g. a cell)?
The products have less free energy than the reactants
Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein?
-∆S, +∆G
Which of the following statements is representative of the second law of thermodynamics?
Cells require a constant input of energy to maintain their high level of organization.
In a particular metabolic pathway, "A" is converted to "B" which is converted to "C". Which of the following is likely to be TRUE about catalysis of the steps in this pathway?
Each step in the pathway will likely be catalyzed by a different enzyme.
Which of the following is a statement of the first law of thermodynamics?
Energy cannot be created or destroyed
Sucrose is a disaccharide composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose results in
breaking of the bond between glucose and fructose and forming new bonds using the atoms from water.
