### Which Of The Following States The Relevance Of The First Law Of Thermodynamics To Biology?

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• 25 Which of the following states the relevance of the first law of thermodynamics to biology? Energy can be freely transformed among different forms as long as the total energy is conserved. Correct.

## Which of the following statements is an application of the first law of thermodynamics for biology?

Answer and Explanation: The correct answer to the above question is: a) Energy cannot be created or destroyed.

#### Which of the following is correct concerning the first law of thermodynamics in biological systems?

Which of the following is correct concerning the first law of thermodynamics in biological systems? The spontaneous direction of a metabolic reaction is dictated by the ratio of substrate and products under equilibrium conditions (K) and under cellular conditions (Q).

## What is entropy in biology?

Learning Outcomes –

Understand how the second law of thermodynamics applies to biological systems

A living cell’s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers we’ve discussed, along with all energy transfers and transformations in the universe, is completely efficient.

1. In every energy transfer, some amount of energy is lost in a form that is unusable.
2. In most cases, this form is heat energy.
3. Thermodynamically, heat energy is defined as the energy transferred from one system to another that is not doing work.
4. For example, when an airplane flies through the air, some of the energy of the flying plane is lost as heat energy due to friction with the surrounding air.

This friction actually heats the air by temporarily increasing the speed of air molecules. Likewise, some energy is lost as heat energy during cellular metabolic reactions. This is good for warm-blooded creatures like us, because heat energy helps to maintain our body temperature. Figure 1. Entropy is a measure of randomness or disorder in a system. Gases have higher entropy than liquids, and liquids have higher entropy than solids. An important concept in physical systems is that of order and disorder (also known as randomness).

The more energy that is lost by a system to its surroundings, the less ordered and more random the system is. Scientists refer to the measure of randomness or disorder within a system as entropy. High entropy means high disorder and low energy (Figure 1). To better understand entropy, think of a student’s bedroom.

If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be put into the system, in the form of the student doing work and putting everything away, in order to bring the room back to a state of cleanliness and order.

This state is one of low entropy. Similarly, a car or house must be constantly maintained with work in order to keep it in an ordered state. Left alone, the entropy of the house or car gradually increases through rust and degradation. Molecules and chemical reactions have varying amounts of entropy as well.

For example, as chemical reactions reach a state of equilibrium, entropy increases, and as molecules at a high concentration in one place diffuse and spread out, entropy also increases. Set up a simple experiment to understand how energy is transferred and how a change in entropy results.

1. Take a block of ice. This is water in solid form, so it has a high structural order. This means that the molecules cannot move very much and are in a fixed position. The temperature of the ice is 0°C. As a result, the entropy of the system is low.
2. Allow the ice to melt at room temperature. What is the state of molecules in the liquid water now? How did the energy transfer take place? Is the entropy of the system higher or lower? Why?
3. Heat the water to its boiling point. What happens to the entropy of the system when the water is heated?

All physical systems can be thought of in this way: Living things are highly ordered, requiring constant energy input to be maintained in a state of low entropy. As living systems take in energy-storing molecules and transform them through chemical reactions, they lose some amount of usable energy in the process, because no reaction is completely efficient.

They also produce waste and by-products that aren’t useful energy sources. This process increases the entropy of the system’s surroundings. Since all energy transfers result in the loss of some usable energy, the second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe.

Even though living things are highly ordered and maintain a state of low entropy, the entropy of the universe in total is constantly increasing due to the loss of usable energy with each energy transfer that occurs. Essentially, living things are in a continuous uphill battle against this constant increase in universal entropy.

#### Which of the following correctly states the relationships between anabolic and catabolic pathways?

what is energy coupling quizlet The more bonds in a molecule, the more potential energy it contains. The coupling reactions in oxidative phosphorylation use a more complicated (and amazing!) Start studying Biology 1, Chapter 8. endergonic: Describing a reaction that absorbs (heat) energy from its environment.a.

This phosphorylation reaction causes a conformational change that allows enzymes to convert the phosphorylated glucose molecule to the phosphorylated sugar fructose. ATP provides the energy for both energy-consuming endergonic reactions and energy-releasing exergonic reactions, which require a small input of activation energy.

What statement best explains the difference in how pH affects the function of this enzyme?The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.As ATP begins to build up in a cell, metabolism slows down. Introduction.

If you’re behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. a) the use of an enzyme to reduce EA b) a barrier to the initiation of a reaction c) a description of the energetic relationship between the reactants and products in an exergonic reaction d) the hydrolysis of ATP to ADP + P e) the use of energy released from an exergonic reaction to drive an endergonic reaction The calculated ∆G for the hydrolysis of one mole of ATP into ADP and PATP is a highly unstable molecule.

mechanism, but the result is the same: the reactions are linked together, the net free energy for the linked reactions is negative, and, therefore, the linked reactions are spontaneous. product: substances that are formed during the chemical change. The apple has potential energy on the tree, and chemical energy in its molecules (which is also potential energy).

If you’re seeing this message, it means we’re having trouble loading external resources on our website. The metabolic energy required to maintain neural activity is very high,,,,In humans, for instance, the brain has only 2% of the body mass and consumes 20% of the human metabolic energy,A large fraction of the total energy consumed by the brain is expended in the generation of the firing sequences of action potentials that neurons use to represent and transmit information,

ATP is required for the phosphorylation of glucose, creating a high-energy but unstable intermediate. As it falls, it has kinetic energy. The use of energy released from an exergonic reaction to drive an endergonic reaction. What statement best explains the difference in how temperature affects the function of this enzyme?At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and waterWhich of these statements about enzyme inhibitors is true?The action of competitive inhibitors may be reversible or irreversible.Which of the following statements about enzyme function is correct?Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.Which of the following correctly states the relationship between anabolic and catabolic pathways?Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.Which of the following statements is correct regarding ATP?The energy in an ATP molecule is released through hydrolysis of one of the phosphate groupsThe process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of _.ATP allosterically inhibits enzymes in ATP-producing pathways.

The result of this is called _.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.Which of the following statements about feedback regulation of a metabolic pathway is correct?The final product of a metabolic pathway is usually the compound that regulates the pathway.A noncompetitive inhibitor decreases the rate of an enzyme reaction by _.Which of the following types of reactions would decrease the entropy within a cell?How does an enzyme increase the rate of the chemical reaction it catalyzes?An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.A chemical reaction that has a positive ΔG is best described as _.why does the reaction rate plateau at higher reactant concentrations?Most enzyme molecules are occupied by substrate at high reactant concentrations.In solution, why do hydrolysis reactions occur more readily than condensation reactions? Cell – Cell – Coupled chemical reactions: Cells must obey the laws of chemistry and thermodynamics.

Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions to harness the energy within the bonds of ATP.Explain the role of ATP as the currency of cellular energyAdenosine triphosphate (ATP) is the energy currency for cellular processes.

• Energy coupling: Energy coupling occurs when the energy produced by one reaction or system is used to drive another reaction or system.
• Chemiosmosis is when ions move by diffusion across a semi-permeable membrane, such as the membrane inside mitochondria.Ions are molecules with a net electric charge, such as Na +, Cl –, or specifically in chemiosmosis that generates energy, H +.During chemiosmosis, ions move down an electrochemical gradient, which is a gradient of electrochemical If you’re seeing this message, it means we’re having trouble loading external resources on our website.

Quizlet.com kinetic energy: capacity to do work- movement potential energy: capacity to do work- chemical bonds which, when broken, release energy) chemical energy: ATP electrical energy: ionic currents reactant: a substance that takes part in and undergoes change during a reaction.

## Which among the following properties is defined by the first law of thermodynamics Mcq?

The first law of thermodynamics is the law of conservation of energy, that is energy cannot be created or destroyed but is converted from one form to another.

### Which among the following is 1st law of thermodynamics for a system in a process?

11.2.1 First law of thermodynamics – The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, but can be transferred from one form to another. As gas turbines are heat engines, converting heat into work, the first law requires that we cannot produce more work than the heat supplied.

#### What is the second law of thermodynamics in biology?

The Second Law of Thermodynamics states that when energy is transferred, there will be less energy available at the end of the transfer process than at the beginning. Due to entropy, which is the measure of disorder in a closed system, all of the available energy will not be useful to the organism.

### What is enthalpy in biology?

Enthalpy in biology refers to energy stored in bonds, and the change in enthalpy is the difference in bond energies between the products and the reactants. A negative ∆H means heat is released in going from reactants to products, while a positive ∆H means heat is absorbed.

## How is energy defined in biology?

Specifically, energy is defined as the ability to do work – which, for biology purposes, can be thought of as the ability to cause some kind of change. Energy can take many different forms: for instance, we’re all familiar with light, heat, and electrical energy.

#### Which term is used to describe a two phase anabolic pathway in which light energy is converted into chemical energy?

Photosynthesis is the anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell.

## Which of the following statements is the reason that most cells Cannot harness heat to perform work?

Answer and Explanation: Because the temperature is usually consistent throughout the cell, most cells cannot employ heat to conduct the cellular activity.

### Which of the following correctly states the second law of thermodynamics?

Second Law of Thermodynamics – Have you ever played the card game 52 pickup? If so, you have been on the receiving end of a practical joke and, in the process, learned a valuable lesson about the nature of the universe as described by the second law of thermodynamics.

In the game of 52 pickup, the prankster tosses an entire deck of playing cards onto the floor, and you get to pick them up. In the process of picking up the cards, you may have noticed that the amount of work required to restore the cards to an orderly state in the deck is much greater than the amount of work required to toss the cards and create the disorder.

See also:  Citizen Who Took The Law Into His Or Her Own Hands?

The second law of thermodynamics states that the total entropy of a system either increases or remains constant in any spontaneous process; it never decreases. An important implication of this law is that heat transfers energy spontaneously from higher- to lower-temperature objects, but never spontaneously in the reverse direction. Figure 12.9 The ice in this drink is slowly melting. Eventually, the components of the liquid will reach thermal equilibrium, as predicted by the second law of thermodynamics—that is, after heat transfers energy from the warmer liquid to the colder ice.

1. Jon Sullivan, PDPhoto.org) Another way of thinking about this is that it is impossible for any process to have, as its sole result, heat transferring energy from a cooler to a hotter object.
2. Heat cannot transfer energy spontaneously from colder to hotter, because the entropy of the overall system would decrease.

Suppose we mix equal masses of water that are originally at two different temperatures, say 20,0 °C 20,0 °C and 40,0 °C 40,0 °C, The result will be water at an intermediate temperature of 30,0 °C 30,0 °C, Three outcomes have resulted: entropy has increased, some energy has become unavailable to do work, and the system has become less orderly.

• Let us think about each of these results.
• First, why has entropy increased? Mixing the two bodies of water has the same effect as the heat transfer of energy from the higher-temperature substance to the lower-temperature substance.
• The mixing decreases the entropy of the hotter water but increases the entropy of the colder water by a greater amount, producing an overall increase in entropy.

Second, once the two masses of water are mixed, there is no more temperature difference left to drive energy transfer by heat and therefore to do work. The energy is still in the water, but it is now unavailable to do work. Third, the mixture is less orderly, or to use another term, less structured.

Rather than having two masses at different temperatures and with different distributions of molecular speeds, we now have a single mass with a broad distribution of molecular speeds, the average of which yields an intermediate temperature. These three results—entropy, unavailability of energy, and disorder—not only are related but are, in fact, essentially equivalent.

Heat transfer of energy from hot to cold is related to the tendency in nature for systems to become disordered and for less energy to be available for use as work. Based on this law, what cannot happen? A cold object in contact with a hot one never spontaneously transfers energy by heat to the hot object, getting colder while the hot object gets hotter. Figure 12.10 Examples of one-way processes in nature. (a) Heat transfer occurs spontaneously from hot to cold, but not from cold to hot. (b) The brakes of this car convert its kinetic energy to increase their internal energy (temperature), and heat transfers this energy to the environment. The reverse process is impossible. (c) The burst of gas released into this vacuum chamber quickly expands to uniformly fill every part of the chamber. The random motions of the gas molecules will prevent them from returning altogether to the corner. We’ve explained that heat never transfers energy spontaneously from a colder to a hotter object. The key word here is spontaneously, If we do work on a system, it is possible to transfer energy by heat from a colder to hotter object. We’ll learn more about this in the next section, covering refrigerators as one of the applications of the laws of thermodynamics. Sometimes people misunderstand the second law of thermodynamics, thinking that based on this law, it is impossible for entropy to decrease at any particular location. But, it actually is possible for the entropy of one part of the universe to decrease, as long as the total change in entropy of the universe increases. In equation form, we can write this as Δ S tot = Δ S syst + Δ S envir > 0, Δ S tot = Δ S syst + Δ S envir > 0, Based on this equation, we see that Δ S syst Δ S syst can be negative as long as Δ S envir Δ S envir is positive and greater in magnitude. How is it possible for the entropy of a system to decrease? Energy transfer is necessary. If you pick up marbles that are scattered about the room and put them into a cup, your work has decreased the entropy of that system. If you gather iron ore from the ground and convert it into steel and build a bridge, your work has decreased the entropy of that system. Energy coming from the sun can decrease the entropy of local systems on Earth—that is, Δ S syst Δ S syst is negative. But the overall entropy of the rest of the universe increases by a greater amount—that is, Δ S envir Δ S envir is positive and greater in magnitude. In the case of the iron ore, although you made the system of the bridge and steel more structured, you did so at the expense of the universe. Altogether, the entropy of the universe is increased by the disorder created by digging up the ore and converting it to steel. Therefore, Δ S tot = Δ S syst + Δ S envir > 0, Δ S tot = Δ S syst + Δ S envir > 0, 12.14 and the second law of thermodynamics is not violated. Every time a plant stores some solar energy in the form of chemical potential energy, or an updraft of warm air lifts a soaring bird, Earth experiences local decreases in entropy as it uses part of the energy transfer from the sun into deep space to do work. There is a large total increase in entropy resulting from this massive energy transfer. A small part of this energy transfer by heat is stored in structured systems on Earth, resulting in much smaller, local decreases in entropy.

## Which of the following thermodynamic law gives the concept of enthalpy Mcq?

Here are 1000 MCQs on Engineering Thermodynamics (Chapterwise),1. What is thermodynamics? a) study of the relationship between heat and other forms of energy b) study of the conversion of chemical energy to other forms of energy c) study of the relationship between mechanical energy to other forms of energy d) study of the conversion of mechanical energy to other forms of energy View Answer Answer: a Explanation: The branch of physical science is concerned with the relationship between heat, and other forms of energy like mechanical, electrical, chemical energy, etc.2.

Which of the following is a branch of thermodynamics? a) Equilibrium thermodynamics b) Classical thermodynamics c) Chemical thermodynamics d) All of the mentioned View Answer Answer: d Explanation: The branches of thermodynamics include: 1) Equilibrium thermodynamics 2) Classical thermodynamics 3) Chemical thermodynamics 4) Statistical mechanics or Statistical thermodynamics 3.

Which of the following is a thermodynamics law? a) Zeroth law of thermodynamics b) Faraday’s Law of thermodynamics c) Ideal Gas Law of thermodynamics d) Boyle’s Law of thermodynamics View Answer Answer: c Explanation: Thermodynamics is primarily based on a set of four rules that are universally applicable when applied to systems that fall within their respective limitations.

• Zeroth law of thermodynamics
• First law of thermodynamics
• Second law of thermodynamics
• Third law of thermodynamics

### Which of the following is a statement related to the first law of thermodynamics?

As per the first law of thermodynamics, energy cannot be created or destroyed.

## Which of the following may be regarded as applying the principle of entropy Mcq?

7. Which of the following may be regarded as applying the principle of entropy? Explanation: These are some general applications of the entropy principle. Explanation: (T1+T2)/2 is when no work is done, and sqrt(T1*T2) is the temperature with maximum work distribution.

#### Which of the following statement is true about first law of thermodynamics it is only applicable for a physical change?

The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic system. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.

#### Which of the following is the first law for a closed system undergoing a cycle Mcq?

According to the First Law of thermodynamics, ‘For a closed system undergoing a cycle, net heat transfer is equal to network transfer.’ ΣQ = ΣW. ∴ Option(3) is the Correct Answer.

#### What is the first law of thermodynamics in biology?

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Page ID 16100 Two fundamental concepts govern energy as it relates to living organisms: the First Law of Thermodynamics states that total energy in a closed system is neither lost nor gained — it is only transformed. The Second Law of Thermodynamics states that entropy constantly increases in a closed system. More specifically, the First Law states that energy can neither be created nor destroyed: it can only change form. Therefore, through any and all processes, the total energy of the universe or any other closed system is constant. In a simple thermodynamic system, this means that the energy is transformed either by the transfer of heat energy (i.e. heating and cooling of a substance) or by the production of mechanical work (i.e. movement). In biological and chemical terms, this idea can be extended to other forms of energy such as the chemical energy stored in the bonds between atoms of a molecule, or the light energy that can be absorbed by plant leaves. Work, in this case, need not imply a complicated mechanism. In fact, there is work accomplished by each molecule in the simple expansion of a heated mass of gaseous molecules (as visualized by expansion of a heated balloon, for example). This is expressed mathematically as the Fundamental Thermodynamic Relation: in which \(E\) is internal energy of the system, \(T\) is temperature, \(S\) is entropy, \(p\) is pressure, and \(V\) is volume. Unlike the First Law which applies even to particles within a system, the Second Law is a statistical law — it applies generally to macroscopic systems. However, it does not preclude smallscale variations in the direction of entropy over time. In fact, the Fluctuation theorem (proposed in 1993 by Evans et al, and demonstrated by Wang et al in 2002) states that as the length of time or the system size increases, the probability of a negative change in entropy (i.e. going against the Second Law) decreases exponentially. So on very small time scales, there is a real probability that fluctuations of entropy against the Second Law can exist. The Second Law dictates that entropy always seeks to increase over time. Entropy is simply a fancy word for chaos or disorder. The theoretical final or equilibrium state is one in which entropy is maximized, and there is no order to anything in the universe or closed system. Spontaneous processes, those that occur without external influence, are always processes that convert order to disorder. However, this does not preclude the imposition of order upon a system. Examining the standard mathematical form of the Second Law: ΔS system + ΔS surroundings = ΔS universe, where ΔS universe > 0 shows that entropy can decrease within a system as long as there is an increase of equal or greater magnitude in the entropy of the surroundings of the system. The phrase “in a closed system” is a key component of these laws, and it is with the idea encapsulated in that phrase that life can be possible. Let’s think about a typical cell: in its lifetime, it builds countless complex molecules – huge proteins and nucleic acids formed from a mixture of small amino acids or nucleotides, respectively. On its surface, this example might seem to be a counterexample to the second law – clearly going from a mixture of various small molecules to a larger molecule with bonded and ordered components would seem to be a decrease in entropy (or an increase in order). How is this possible with respect to the second law? It is, because the second law applies only to closed systems. That is, a system that neither gains nor loses matter or energy. The “universe” is a closed system by definition because there is nothing outside of it. A living cell is not a closed system: it has inputs and outputs. However, the second law is still useful if we recognize that the only way that it can be bypassed is through the input of energy. If a cell cannot take in food (input of matter and energy into the system) it dies, because the second law requires that everything eventually breaks down into more random/chaotic collections of smaller components. The order required to sustain life (think about all the different complex molecules that were mentioned in the previous chapter) is phenomenal. The same thing applies on the organismal level (Figure \(\PageIndex \)) – without an input of energy (in the form of food molecules for animals or in the form of light for plants), the organism will die and subsequently decompose. Figure \(\PageIndex \). In the top panel, depicting an open system in which there are inputs for matter and energy (in the form of food), the box is open and air can be exchanged, food dropped in, etc, thus allowing the mouse to grow. However, in the bottom panel, depicting a closed system, the mouse does not have ready access any more oxygen than is in the box, nor does it have access to food. Without these inputs, the second law takes effect, and the mouse dies and decomposes into many smaller molecules. Creating molecules from atoms costs energy because it takes a disordered collection of atoms and forces them, through chemical bonds, into ordered, non-random positions. There is likewise an energy cost to formation of macromolecules from smaller molecules. By imposing order in the system, there must be an associated input of energy. This happens at every level of the system: atoms to molecules, small molecules to macromolecules, groups of molecules to organelles, etc. As the polymerizing reaction reduces entropy, it requires energy generated (usually) by the breakdown of ATP into AMP and PPi, which is a reaction that increases entropy. Where does that energy go? It ends up in the bonds that are holding the molecules or macromolecules in their ordered state. When such a bond is broken, and a molecule is turned back into a collection of atoms, energy is released. The energy in a chemical bond is thus potential energy – it is stored energy that, when released, has the ability to do work. This term, if you recall your high school physics, is usually learned along with kinetic energy, which is energy that is being used in the process of actually doing work (i.e. moving an object from one place to another). The classic example is the rock on the top of a hill: it has potential energy because it is elevated and could potentially come down. As it tumbles down, it has kinetic energy as it moves. Similarly in a cell, the potential energy in a chemical bond can be released and then used for processes such as putting smaller molecules together into larger molecules, or causing a molecular motor to spin or bend – actions that could lead to pumping of protons or the contraction of muscle cells, respectively. Coming back to the second law, it essentially mandates that breaking down molecules releases energy and that making new molecules (going against the natural tendency towards disorder) requires energy. Every molecule has an intrinsic energy, and therefore whenever a molecule is involved in a chemical reaction, there will be a change in the energy of the resulting molecule(s). Some of this change in the energy of the system will be usable to do work, and that energy is referred to as the free energy of the reaction. The remainder is given off as heat. The Gibbs equation describes this relationship as \ where ΔG is the change in free energy, ΔH is the change in enthalpy (roughly equivalent to heat), T is the temperature at which the reaction takes place, and ΔS is the change in entropy. As a matter of convention, release of free energy is a negative number, while a requirement for input of energy is denoted with a positive number. Generally, a chemical reaction in which ΔG 0 is not spontaneous (or endergonic). When ΔG = 0, the system is in equilibrium. ΔG can also be expressed with respect to the concentration of products and reactants: \ Terms in square brackets denote concentrations, ΔG° is the standard free energy for the reaction (as carried out with 1M concentration of each reactant, at 298K and at 1 atm pressure), R is the gas constant (1.985 cal K -1 mol -1 ), and T is the temperature in Kelvin. In a simpler system in which there are just two reactants and two products: \ the equation for free energy change becomes ΔG = ΔG° + RTln( c d / a b ) This is important to us as cell biologists because although cells are not very well suited to regulating chemical reactions by varying the temperature or the pressure of the reaction conditions, they can relatively easily alter the concentrations of substrates and products. In fact, by doing so, it is even possible to drive a non-spontaneous reaction (ΔG > 0) forward spontaneously (ΔG < 0) either by increasing substrate concentration (possibly by transporting them into the cell) or by decreasing product concentration (either secreting them from the cell or by using them up as substrates for a different chemical reaction). Changes in substrate or product concentration to drive a non-spontaneous reaction are an example of the more general idea of coupling reactions to drive an energetically unfavorable reactions forward. Endergonic reactions can be coupled to exergonic reactions as a series of reactions that ultimately is able to proceed forward. The only requirement is that the overall free energy change must be negative (ΔG < 0). So, assuming standard conditions (ΔG = ΔG°'), if we have a reaction with a free energy change of +5 kcal/mol, it is non-spontaneous. However, if we couple this reaction, to ATP hydrolysis for example, then both reactions will proceed because the standard free energy change of ATP hydrolysis to ADP and phosphate is an exergonic -7.3 kcal/mol. The sum of the two ΔG values is -2.3 kcal/mol, which means the coupled series of reactions is spontaneous. In fact, ATP is the most common energy "currency" in cells precisely because the -7.3 kcal/mol free energy change from its hydrolysis is enough to be useful to drive many otherwise endergonic reactions by coupling, but it is less costly (energetically) to make than other compounds that could potentially release even more energy (e.g. phosphoenolpyruvate, PEP). Also, much of the -14.8 kcal/mol (ΔG°') from PEP hydrolysis would be wasted because relatively few endergonic reactions are so unfavorable as to need that much free energy. Why is ATP different from other small phosphorylated compounds? How is it that the γ-phosphoanhydride bond (the most distal) of ATP can yield so much energy when hydrolysis of glycerol-3-phosphate produces under a third of the free energy? The most obvious is electrostatic repulsion. Though they are held together by the covalent bonds, there are many negative charges in a small space (each phosphate carries approximately 4 negative charges). Removing one of the phosphates significantly reduces the electrostatic repulsion. Keeping in mind that DG is calculated from the equilibrium of both reactants and products, we also see that the products of ATP hydrolysis, ATP and phosphate, are very stable due to resonance (both ADP and Pi have greater resonance stabilization) and stabilization by hydration. The greater stability of the products means a greater free energy change. Even when a reaction is energetically favorable (ΔG activation energy, and it overcomes thermodynamic stability. Consider glucose, for instance. This simple sugar is the primary source of energy for all cells and the energy inherent within its bonds is released as it breaks down into carbon dioxide and water. Since this is large molecule being broken down into smaller ones, entropy is increased, thus energy is released from reaction, and it is technically a spontaneous reaction. However, if we consider a some glucose in a dish on the lab bench, it clearly is not going to spontaneously break down unless we add heat. Once we add sufficient heat energy, we can remove the energy source, but the sugar will continue to break down by oxidation (burn) to CO 2 and H 2 O. Figure \(\PageIndex \). Catalysts lower the activation energy barrier to chemical reactions without altering the free energy change for that reaction. Put another way, the reactant(s) must be brought to an unstable energy state, known as the transition state (as shown at the peak of the graphs in Figure \(\PageIndex \)).

• This energy requirement barrier to the occurrence of a spontaneous thermodynamically favored reaction is called the activation energy.
• In cells, the activation energy requirement means that most chemical reactions would occur too slowly/infrequently to allow for all the processes that keep cells alive because the required energy would probably come from the chance that two reactants slam into one another with sufficient energy, usually meaning they must be heated up.

Again, cells are not generally able to turn on some microscopic Bunsen burner to generate the activation energy needed, there must be another way. In fact, cells overcome the activation energy problem by using catalysts for their chemical reactions. Broadly defined, a catalyst is a chemical substance that increases the rate of a reaction, may transiently interact with the reactants, but is not permanently altered by them.

## What are the applications of first law of thermodynamics?

The first law of thermodynamics is commonly used in heat engines. Refrigerators is another example where the first law of thermodynamics is used. Sweating is a great example of the first law of thermodynamics since the heat of the body is transferred to sweat.

## What are the applications of thermodynamics in the biological system?

The laws of thermodynamics are important unifying principles of biology, These principles govern the chemical processes (metabolism) in all biological organisms. The First Law of Thermodynamics, also known ​as the law of conservation of energy, states that energy can neither be created nor destroyed.

It may change from one form to another, but the energy in a closed system remains constant. The Second Law of Thermodynamics states that when energy is transferred, there will be less energy available at the end of the transfer process than at the beginning. Due to entropy, which is the measure of disorder in a closed system, all of the available energy will not be useful to the organism.

Entropy increases as energy is transferred. In addition to the laws of thermodynamics, the cell theory, gene theory, evolution, and homeostasis form the basic principles that are the foundation for the study of life.