BIOL - Topic 8
When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, enthalpy and entropy are as follows
+∆H, -∆S, +∆G
How does energy from ATP allow some of the reactions of anabolism to occur?
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 Energy from ATP is used to increase the potential energy of a reactant molecule, such that the total free energy of the reactant molecule is now greater than the total free energy of the product molecule that would be formed by the reaction
Which of the following 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
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
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 is TRUE for ALL exergonic reactions?
If the reaction proceeds, there will be a net decrease in free energy
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 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 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
The mathematical expression for the change in the free energy of a system is ∆G = ∆H - T∆S. Which of the follow is (are) TRUE?
T is the temperature in degrees Kelvin
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
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
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
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 considered an open system?
a clam an animal cell a plant cell with a strong cell wall
Which of the following is an example of potential rather than kinetic energy?
a food molecule
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
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
Spontaneous reactions
do not require an energy input to occur
ATP is formed
during many catabolic reactions by many exergonic reactions during hydrolysis of many biological polymers (e.g. carbohydrates, lipids, and proteins)
A chemical reaction that has a positive ∆G is correctly described as
endergonic
Which of the following is a statement of the first law of thermodynamics?
energy cannot be created or destroyed
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)
The ATP used by the cell for energy coupling
has three phosphate groups is identical to one of the four nucleotides used for RNA synthesis is a high energy molecule due to having unstable covalent bonds
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
The statement "energy cannot be created or destroyed"
is a statement of the first law of thermodynamics
"Every energy transfer or transformation increases the entropy of the universe"
is a statement of the second law of thermodynamics
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
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
If most metabolic reactions are reversible, why is equilibrium rarely reached for these reactions?
most of the products of the reactions are removed from the system
In an isolated system
neither energy nor matter can leave the system
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
Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell
A consequence of the 1st and 2nd laws of thermodynamics is
that the total amount of energy in the universe that is available to perform work is always decreasing that, according to some theories, at some point in the far distant future the temperature across the universe will be ~ constant that, according to some theories, at some point in the far distant future there will be no more energy in the universe that is able to do work
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 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
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 different 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
"Conservation of energy" is another way of stating
the first law of thermodynamics
At zero degrees Kelvin, in theory,
you will be frozen entropy will reach a minimum value water will be frozen
