Chapter 3 quiz
an endothermic process that increases entropy in a setting with a high temperature.
This can be spontaneous. An example of an endothermic reaction that results in an increase in entropy in a setting with a high temperature is evaporating water on a hot day. The water releases the trapped thermal energy as a result of a phase change, which decreases the entropy of the system.
Provide an example of a use of ATP energy for each of the following tasks: a) chemical work
An example of chemical work using ATP is supplying energy for non-spontaneous, endergonic reactions, including protein synthesis and DNA replication.
Describe the structure of an ATP molecule.
ATP can be described as a phosphorylated sugar. It has a triphosphate group attached to a ribose sugar molecule, which is attached to a molecule of adenosine.
Describe the process of ATP hydrolysis.
ATP hydrolysis is the process by which ADP and Pi are formed and water is consumed. The process releases free energy.
Provide an example of a use of ATP energy for each of the following tasks: mechanical work
An example of mechanical work using ATP energy is the beating of cilia or movement of flagella, contraction of muscle fibres, or movement of chromosomes during mitosis/meiosis.
Provide an example of a use of ATP energy for each of the following tasks: transport work
An example of transport work using ATP energy is pumping substances such as Na+ or K+ ions across membranes against their concentration gradient.
Examine the graphs in Figure 6, depicting reaction pathways. Which of these two reactions would benefit the most by the addition of an enzyme? Explain your reasoning.
Assuming that the two y axes have the same scale, and the two reactions are under similar conditions, reaction B appears to have the highest activation energy so would benefit the most by the addition of an enzyme.
Free energy and spontaneous changes
A change that will, once begun, continue on its own under a given set of conditions; does not require a continuous supply of energy. Free energy is energy available to do work and spontaneous changes result in a reduction of free energy in the system
Explain, in your own words, why both gasoline and glucose make good fuels.
Both gasoline and glucose make good fuels. Chemically both compounds contain a very high percentage of high-energy C-H bonds. When these molecules react with oxygen, their high-energy valence electrons form strong bonds with the very electronegative oxygen atoms, causing the release of energy. In cars, a liquid fuel is advantageous as it is easy to transport. In organisms, a solid fuel that can be dissolved within the body is advantageous as it allows for easy storage and transport throughout the body and easy absorption from food sources.
How is it beneficial for organisms to use controlled oxidation rather than rapid combustion to release energy from their food? Provide at least two benefits.
Controlled oxidation is a benefit to an organism because less energy is lost or wasted as thermal energy during controlled oxidation than would be lost during rapid oxidation. In addition, the cell could suffer damage from the high temperatures required energy during controlled oxidation than would be lost during rapid oxidation. In addition, the cell could suffer damage from the high temperatures required, and created, by rapid combustion.
During the hydrolysis of ATP, energy is released, but most of the molecule, the ADP portion, remains intact. How does this compare to what happens to a molecule of glucose when it is used as an energy source?
During the hydrolysis of ATP the ADP is retained and recycled. This is in contrast to the oxidation of glucose, in which the entire molecule is catabolized. When a cell uses glucose during cellular respiration the entire molecule is oxidized and converted into water and carbon dioxide.
What atom is reduced by gaining an electron during the reduction of NAD+?
During the reduction of NAD+ the nitrogen atom in the ring gains an electron.
Some enzymes are ingredients in cleaning solutions for contact lenses. They catalyze the breakdown of proteins that can accumulate on the surface of a lens. Suggest a possible name for this type of enzyme.
Enzymes that break down proteins are given the general name proteases.
an exothermic process that decreases entropy in a setting with a high temperature.
Exothermic process that decreases entropy in a setting with a high temperature are not generally spontaneous.
Explain how organisms can grow and create internal order without violating the second law of thermodynamics.
In order to see that an organism can grow and create internal order without violating the second law of thermodynamics, you must take both the organism and its surroundings into account. The organism experiences a decrease in entropy, but it must have a continual supply of energy to do this. Also, the cell expels waste products and waste thermal energy to its surroundings such that the entropy of the total system increases.
Potential energy and kinetic energy
Kinetic energy occurs as a result of motion. Potential energy is stored within an object and is dependent on the object's location or chemical structure. Energy can be transferred from stored energy (Potential) to movement (Kinetic).
Why is relying solely on increasing temperature not a good strategy to reach activation energy requirements in living organisms? What is the benefit of enzymes?
Relying solely on increasing temperature to reach activation energy is not a good strategy since high temperatures can cause cell damage and death. Increasing temperature in general will also cause an increase in all reactions in a cell. The benefit of enzymes is they help particular reactions to initiate without high temperatures.
What atom is reduced by bonding to an added hydrogen atom?
The carbon opposite to the nitrogen in the ring is reduced by bonding to an additional hydrogen atom.
In your own words, describe the difference between anabolic and catabolic pathways.
The difference between anabolic and catabolic pathways is the change in free energy as a result of the reaction. An anabolic pathway is a process in which complex molecules are built from simpler ones, requiring free energy. A catabolic pathway is a process in which large complex molecules are broken down into simpler ones, releasing free energy
Describe the relationship between bond energy and energy changes that occur during a chemical reaction.
The relationship between bond energy and energy changes that occur during a chemical reaction is bond energy is the energy needed to break a bond and energy changes that occur are a result of the comparison between the chemical potential energy of the products and the chemical potential energy of the reactants. During any chemical reaction some energy is absorbed when bonds in the reactants break and some energy is released when bonds form in the products. This change in bond energy is measured as the energy change of a reaction.
Describe the first and second laws of thermodynamics.
The second law of thermodynamics state that In every energy transfer or conversion, some of the useful energy in the system becomes unusable and increases the entropy of the universe. The first law of thermodynamics states that the total amount of energy in any closed system is constant. Energy cannot be created or destroyed; it can only be converted from one form to another.
How does the structure of the ATP molecule relate to the large amounts of free energy it contains?
The structure of an ATP molecule allows it to contain large amounts of free energy. The unique feature that allows ATP to do this is its triphosphate tail. The triphosphate tail is the location of several high energy bonds that can be recycled using the cellular machinery.
Many spontaneous reactions occur very slowly. If they can occur, why do all spontaneous reactions not take place immediately?
The term spontaneous in chemical reactions refers to the reaction's ability to progress from reactants to products and not the rate at which this will occur. Many spontaneous reactions don't take place immediately because many of the reactions require high activation energies. Therefore, it can take a great deal of time for the reactants to acquire the necessary activation energy and have enough successful collisions to occur. These reactions will occur spontaneously but slowly.
What are the three mechanisms by which an enzyme lowers the activation energy of a reaction?
The three mechanisms by which an enzyme lowers the activation energy of a reaction are: enzymes can bring reactants closer together, enzymes can bring the substrate into a charged environment, and enzymes can distort or bend substrates.
What does the universality of ATP in all living species suggest about the relationship of species to one another?
The universality of ATP as an energy source for every type of cell in every living organism supports an argument that all species have evolved from one original organism.
an endothermic process that decreases entropy in a setting with a low temperature.
There are no endothermic processes that decrease entropy at low temperatures. These reactions are nonspontaneous.
Does this reaction influence any other atoms in the nicotinamide structure?
There is a reduction in the number of double bonds in the nicotinamide ring structure but the other atoms in nicotinamide don't change.
Suggest a benefit provided by some of the waste energy that is released during cellular redox reactions.
Thermal energy released during cellular redox reactions helps us to maintain a body temperature which is generally greater than the temperature in our surroundings and also increases the available thermal energy for other chemical reactions, reducing the needed activation energy.
Which of the following processes are spontaneous? Give an example of each spontaneous process. a) an exothermic process that increases entropy in a setting with a low temperature.
This can be spontaneous. An example of a spontaneous exothermic process that increases entropy in a setting with a low temperature would be the combustion of wood in the winter.
List two examples of slow oxidation events and two examples of rapid oxidation events.
Two examples of slow oxidation events are the formation of patina on copper roofs and the rotting of fruits. Two examples of rapid oxidation are the burning of gasoline and the light given off from a road flare.
A bacterial cell propels itself through water using a flagellum.
When a bacterial cell propels itself using a flagellum, this is non-spontaneous. The bacterial cell requires a source of free energy to move its flagellum. The bacteria would obtain this free energy by coupling the reactions needed to move the flagellum to exergonic chemical reactions
Is the releasing of light by a firefly endergonic or exergonic? Explain how such a process abides by the first and second laws of thermodynamics.
When a firefly releases light energy, the overall process must be exergonic. The production of light requires a source of free energy and this energy must have been supplied by an exergonic chemical reaction. This process abides by the first law of thermodynamics because chemical energy is being converted into light energy but energy is not being created or destroyed. It abides by the second law of thermodynamics because in producing the light the firefly would also release a small amount of waste energy, that is, the conversion from chemical to light energy would not have been 100 % efficient.
Honey bees perform a hydrolysis reaction to convert sucrose into a mixture of glucose and fructose.
When a honey bee converts sucrose into glucose and fructose, this is a spontaneous reaction because it is a catabolic/exergonic reaction in which entropy increases. Bees might do this by converting sucrose they obtained from plants into honey.
Electric eels generate powerful electric fields to stun their prey and to defend themselves.
When an electric eel creates an electric field, this would be a non-spontaneous process since the eel would need a source of free energy. The eel would convert chemical potential energy in its food to electrical energy generated by specialized cells in its body.
Explain why some people might mistakenly think that living things do not obey the second law.
When living things grow they become more orderly not less orderly, so it appears as if their actions reduce entropy. However, while their bodies may become more ordered, they release waste particles and waste thermal energy that results in an overall increase in entropy.
For each of the following, state whether the event or process is spontaneous or nonspontaneous, and under what conditions you would expect it to occur. a) Organic food waste decomposes.
When organic food waste decomposes, this is a spontaneous reaction. It is a catabolic process and results in an increase in entropy. It would occur when bacteria or fungi release digestive enzymes onto the food waste that break large molecules into smaller molecules, releasing energy for the bacteria or fungi to use.
Energy and work
Work is performed when energy is used to move an object against an opposing force, such as friction or gravity. Energy is defined as the capacity to do work.
