BIO lecture 8 study questions
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
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.
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?
Both A and B are correct: 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 endergonic reaction.; Energy from ATP is often used to help combine an exergonic reaction with a reaction that would otherwise be endergonic
Which of the following statements is representative of the second low of thermodynamics?
Cells require a constant input of energy to maintain their high level of organization
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 types of reactions would decrease the entropy of a cell?
dehydration reactions
Spontaneous reactinos
do not require an energy input to occur
A chemical reaction that has a positive ∆G is correctly described as
endergonic
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
The total energy of a biological system is represented by
enthalpy (H)
Whenever energy is transformed, there is always an increase in the
entropy of the universe
Choose the pair of term that correctly completes this sentence: Catabolism is to anabolism as __ is to __.
exergonic; endergonic
The hydrolysis of ATP to form ADP and Pi is
highly exergonic
Which of the following best describes enthalpy (H)?
in biological systems, enthalpy is equivalent tot total energy
Free energy (G)
is a measure of the energy in a system that is available to do work
"Every energy transfer or transformation increases the entropy of the universe"
is a statement of the second law of thermodynamics
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
Energy that goes to increase the entropy of the universe is
no longer available to perform work
What is the change in free energy of a system at chemical equilibrium?
no net change
Which of the following statements is FALSE?
Hydrolysis of ATP to form ADP and inorganic phosphate is a highly endergonic reaction
How do living organisms create macromolecules, organelles, cells, tissues, and complex higher-order structures?
Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe as a whole
If most metabolic reactions are reversible, why is equilibrium rarely reached for those reactions?
Most of the products of the reactions are removed from the system.
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.
When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free enthalpy and entropy are as follows:
+∆H, -∆S, +∆G
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?
all of these answers are correct: an animal cell, a plant cell with a strong cell wall, a clam
The rate of flow of materials through a metabolic pathway can be altered by
all of these answers are correct: changing the activity level(s) of one or more of the enzymes that catalyze steps in that pathway, altering the amount of substrate for the reaction, altering the amount of product for the reaction
ATP is formed
all of these answers are correct: during hydrolysis of many biological polymers (e.g. carbohydrates, lipids and proteins), during many catabolic reactions, by many exergonic reactions
How does energy from ATP allow some of the reactions of anabolism to occur?
all of these answers are correct: energy from ATP is used to increase the potential energy of a reactant molecule, such that the total free energy of the reactant molecules is now greater than the total free energy of the product molecules that would be formed by the reaction; a phosphate group is transferred from ATP to a reactant molecule, raising the energy level of that reactant molecule; some of the energy from a high energy covalent bond in the ATP molecule is used to form a high energy covalent bond in a substrate molecule
The ATP used by the cell for energy coupling
all of these answers are correct: is identical to one of the four nucleotides used for RNA synthesis, is a high energy molecule due to having unstable covalent bonds, has three phosphate groups
A consequence of the 1st and 2nd laws of thermodynamics is
all of these answers are correct: that, according to some theories, at some point in the far distant future there will be no more energy in the universe that is available to do work; that, according to some theories, at some point in the far distant future the temperature across the universe will be ~ constant; that the total amount of energy in the universe that is available to perform work is always decreasing
At zero degrees Kelvin, in theory,
all of these answers re correct: water will be frozen, you will be frozen, entropy will reach a minimum value
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
Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell
A consequence of the fat 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 H2O What 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 molecules + 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
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
Living organisms don't violate the 2nd law of thermodynamics because:
they typically increase the entropy of their surroundings
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.
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 TRUE for ALL exergonic reactions?
If the reaction proceeds there will be a net decrease in free energy.
When ATP releases some energy, it also releases inorganic phosphate. What purpose, if any, does this serve in the cell?
It can be added to other molecules in order to activate them
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
When sodium chloride (table salt) crystals dissolve in water, the temperature of the solution decreases. This means that, for dissociation of Na+ and Cl- ions,
The change in enthalpy (∆H) is positive, but the change in entropy is greater.
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 is TRUE for all endergonic reactions in open systems (e.g. a cell)?
The products have more free energy than the reactants
A reaction has a ∆G of -5.6 kcal/mol. Which of the following would most likely be TRUE?
The reaction would result in an increase in entropy (S) and a decrease in the energy content (H) of the system
Which of the following statements about biological systems is FALSE?
The total energy in a biological system cannot increase or decrease
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
Which of the following is (are) TRUE for anabolic pathways?
They consume energy to build up polymers from monomers?
Which of the following is considered an open system?
an organism
The synthesis of polymers from their constituent monomers occurs during
anabolism
The breakdown of polymers to their constituent monomers occurs during
catabolism
which term precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
