Tutorial 26 Thermodynamics

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Adenosine triphosphate (ATP) An energy-rich molecule that supplies the energy for most cellular reactions and is found in the cells of all living thing
endergonic reaction A chemical reaction in which the free energy of the products is greater than the free energy of the reactants. Free energy must be put into the reaction for it to proceed.
Energy That which can and does move matter; the capacity to do work.
energy coupling A transfer of energy from an exergonic process to an endergonic process to drive a reaction.
entropy (S) A measure of disorder within a system.
exergonic reaction A reaction where energy is released.
free energy (G) The energy in a system that can be converted to do work.
kinetic energy Energy that a body possesses due to being in motion.
metabolism The sum of all the chemical reactions that occur in living organisms.
nonspontaneous reaction An endergonic reaction.
potential energy Energy that a body possesses due to its position.
spontaneous reaction An exergonic reaction.
thermodynamics A branch of physics that deals with the energy and work of a system.
glycolysis The catabolic breakdown of carbohydrates.
Kreb's cycle The citric acid cycle.
What are the two types of metabolic reactions? Anabolic and catabolic.
What type of reactions are involved in photosynthesis? Anabolic.
What type of reactions are involved in chemoheterotrophy? Catabolic.
What is a synonym for potential energy? Stored energy.
What is the temperature of an object reflective of? The kinetic energy of its atoms or molecules.
How do chemical bonds form? As a result of electron behavior.
In the vast majority of metabolic reactions, what is the vehicle for moving energy? Electrons.
What is the reaction involved when methane combines with oxygen? CH4 + 2O2 –> CO2 +2H20
How much energy is required to break bonds for every mole of methane reacting with two moles of oxygen? 632 kcal
How much energy is evolved as new bonds form in association with oxygen in the methane combustion reaction? 792 kcal
What is the higher unit for 1 kcal? 1 Cal.
Thermodynamics The physics of energy transformations that occur in a collection of matter.
System Any collection of matter under thermodynamic scrutiny.
First law of thermodynamics. Energy is neither created nor destroyed.
What does bookkeeping mean in regards to the first law of thermodynamics? The energy used and released in any reaction must be balanced; e.g., the energy in one molecule can be distributed into two or more other molecules.
Second law of thermodynamics All energy-affected matter in the universe is becoming random; i.e., the total entropy is increasing.
What does it take to maintain order in a system? Input of energy.
How can any order be achieved if the tendency for matter in the universe is toward ever-increasing entropy? Systems can become ordered as long as they are "open" to the universe.
What is the reaction for breaking down glucose? C6H12O6 + 6O2 –> 6CO2 + 6H20 + E
What is the energy obtained by organisms ultimately used for? To reverse entropic change.
What happens if you stop eating? You will die due to lack of energy input from without.
What does the second law of thermodynamics favor for a glucose molecule? Breakdown of the glucose molecule into CO2 and H2O molecules.
For the majority of life forms on Earth, where does energy ultimately come from? The sun.
What is the special relationship between temperature and entropy? The entropic state of a given system is proportional to temperature.
What is the symbol for entropy? S
What is the symbol for free energy? G
What is possible if a system releases free energy? It can do work.
What is possible if a system absorbs free energy? Work can be done upon it.
What is ?G? The change in free energy.
What makes ?G endergonic? If energy enters the system, the reaction is nonspontaneous, and has a +?G
What makes ?G exergonic? If energy leaves the system, which is an unstable (spontaneous) reaction, and has a -?G.
Why do reactions not transduce 100% of the available energy? All energy transfers have some inefficiencies.
Why is not all the total energy in a system available to do work? Free energy is a function of the total energy change of a system and the entropic change.
Enthalpy The total energy in a system.
What takes place with negative enthalpy? Some energy, typically heat, will leave the system.
What takes place with positive enthalpy? Energy (typically heat aborbed from outside) will enter the system.
exothermic reaction A reaction that has a negative -?H and will release heat.
endothermic reaction A reaction that has a positive +?H and will release heat.
What is free energy dependent on? Temperature.
What is the free energy equation? ?G = ?H – T(?S)
What happens when ?G becomes more negative? The free energy released by the reaction is greater.
What happens when ?G becomes more positive? The energy required for the reaction to proceed increases.
What are the reactions involved in breaking down glucose to retrieve energy during cellular respiration? Exergonic.
What is the cellular respiration reaction? C6H12O6 + 6 O2 —-> 6 CO2 + 6 H2O
What is the ?G of the glycolosis reaction? -686 kcal per mole of glucose.
What is the photosynthesis reaction? 6 CO2 + 6 H2O —-> C6H12O6
What is the ?G of the photosynthesis reaction? +686 kcal/mole.
Where does the energy come from for the endergonic reaction of photosynthesis? The sun.
What is the structure of ATP? A 5-carbon sugar (ribose) attached to a nitrogenous base (adenine), and a group of three phosphates.
What is important about the three phosphates in ATP? They are very unstable due to three negative charges creating strain in one area of the molecule.
What do most reactions involving ATP depend on? Hydrolysis of the third phosphate to liberate the potential energy that can be used to do work.
What are released during ATP hydrolysis? Free energy, ADP, and inorganic phosphate (Pi).
How is energy made available in a cell? From the hydrolysis of ATP to ADP + Pi, which provides energy for endergonic reactions.
Why is glutamine synthesis a thermodynamically unfavorable reaction? The ?G for this reaction is + 3.4 kcal/mol; coupling the removal of the terminal phosphate of ATP and the addition of ammonia to glutamic acid provides the energy.
What is the ?G of the hydrolysis of ATP to ADP and Pi? -7.3 kcal/mol.
Why is the energy coupling procedure so important? It allows many endergonic anabolic reactions to occur in the cell.
A molecule that is reduced has what features? It gains electrons from another molecule and has a higher energy level.
What is the transfer of free energy from catabolic pathways to anabolic pathways through a phosphorylated intermediate such as when ATP is hydrolyzed? Energy coupling.
In an endergonic reaction, what is the relationship between the reactants and the products? The products have more energy than the reactants.
In an exergonic reaction, what is the relationship between the reactants and the products? The reactants have more energy than the products.
Cell metabolism is driven by what? Both endergonic and exergonic reactions.

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