Lecture 3

Question 1

What does free energy tell you ?

Answer 1

• tells us if process requires or releases energy

– release of energy can be used to do cellular work: protein synthesis, folding of proteins, transport across membranes

Question 2

What is a system?

Answer 2

• any part of universe we are studying –> anything else is surroundings
  ex: you want to see how much energy it will take to lift a book in ur room (book = system; room = surrounding)

Question 3

What is an isolated system?

Answer 3

• unable to exchange energy or matter with surroundings

Question 4

What is a closed system?

Answer 4

– able to exchange energy, but not matter with surroundings

Question 5

What is an open system?

Answer 5

• able to exchange energy and matter surroundings

Question 6

T or F, organisms are typically open systems

Answer 6

True; ex: energy –> heat, matter –> waste like sweat

Question 7

What are the two laws of thermodynamics state?

Answer 7

– 1st law: total energy of a system and its surroundings is constant. Cannot be created or destroyed, but it can be transferred –> through energy or work

– 2nd law: total entropy (disorder) of a system plus its surroundings always increases

Question 8

T or F, as energy is being lost to work an equal amount of energy must be absorbed

Answer 8

T, think of closed system

Question 9

In the case of muscle contraction ATP is used for the movement of muscle contractions, what would need to happen next in a closed system?

Answer 9

– ATP after being used in turn is generated from the metabolic reactions that extracted energy in the form of ATP from nutrients like carbohydrates, fats or proteins

Question 10

What is a variable that can be used to measure the amount of heated released from a reaction?

Answer 10

• It is called enthalpy and it is the energy released or needed to break or make bonds. Enthalpy is the internal energy of the system

Question 11

true or false. a reaction at equilibrium is at its lowest energy state.

Answer 11

true; because free energy here is = to 0

Question 12

What are the three ways where entropy can be changed?

Answer 12

– ability of molecule to rotate/vibrate/twist around bonds

– molecules overall scattered or ordered (i.e. cell)

– larger molecules vs. smaller molecules (less entropy vs. more). –> smaller molecules would have more entropy

Question 13

T or F, energy considerations determine if a reaction will proceed in one direction or occur in reverse direction

Answer 13

True

Question 14

What is free energy dependent on?

Answer 14

Enthalpy and Entropy

Question 15

A lot of our structures in our body are very ordered and complex. How does nature compensate for the increases order of our body?

Answer 15

– by increasing entropy of the surrounding

Question 16

How do you find the entropy of the surroundings? What is another way to write free energy symbol?

Answer 16

• • divide enthalpy of system by temperature (kelvin).

- - Can also be written as -T*entropy of the universe.

Question 17

A reaction is held where the total number of molecules between each side is held the same. At the same time, stronger bonds are formed in the products. Could this be considered a favorable reaction?

Answer 17

• • Yes. Since entropy didn’t change, there is no entropic favorability for the reaction.
• • However, because stronger bonds are formed, a more stable conformation (lower energy) product is form. This causes a release of a lot of heat, which is favorable in terms of free energy

– with bonds –> energy is released when bonds are formed

– The stronger the bond formed, the more energy is released during the bond formation process.

Question 18

If products are found to be at a lower free energy than that of their products, is the reaction exothermic?

Answer 18

– no. the reaction is exergonic.

–> exergonic is when you lose energy

– exothermic is a property of enthalpy and it can’t be known for sure if heat is released or if this is a result of very favorable entropy.

Question 19

T or F, a decrease in enthalpy is favorable where as an increase in entropy is also favorable

Answer 19

True, we want there to be less order, and also a negative change in enthalpy favors a reaction proceeding because it’s losing heat

Question 20

T or F, when deltaH s positive and deltaS is negative, delta G will still be negative, and the reaction will be favorable @ any temperature

Answer 20

False, deltaH is positive and delta S is negative –> deltaG is always positive and the reaction is not favorable at any temperature

Question 21

What is the difference between a positive, negative and zero value for a change in free energy?

Answer 21

– negative value: reaction proceeds to the right spontaneously; favorable to proceed in forward direction (exergonic)

– positive value: unfavorable in the forward direction but favorable in the reverse direction (bc in the reverse it would have a negative sign)

– zero value means that system is at equilibrium –> can go both towards right and towards left

Question 22

How do you calculate the change in free energy with the change in free energy under standard condition?

Answer 22

• deltaG = deltaGprime + RTln [C x D]/[A x B]

- standard conditions for concentration of H+ is 10^-7 M –> have to divide 10^ (whatever pH)

Question 23

T or F, we must have a delta G prime to calculate change in free energy or have a known Keq

Answer 23

True; change in free energy of reaction changes from value it was under standard conditions

Question 24

T or F, every biochemical process must be thermodynamically favorable to proceed

Answer 24

True

Question 25

T or F, reactions can’t be coupled

Answer 25

False, reactions can be coupled

Question 26

A lot of our structures in our body are very ordered and complex. How does nature compensate for the increases order of our body?

Answer 26

By increasing entropy of surrounding –> think of balance

Question 27

If products are found to be at a lower free energy than that of their reactants, is the reaction exothermic?

Answer 27

– no. the reaction is exergonic. –exothermic is a property of enthalpy and it can’t be known for sure if heat is released or if this is a result of very favorable entropy.

Question 28

If free energy is small, can it be considered reversible. How about for large Free energy?

Answer 28

– Yes. small free energy means the reaction is close to equilibrium and neither side is really favored.

–For large free energies, the reaction is basically physiologically irreversible and can’t occur the opposite direction

Question 29

True or false. The equilibrium constant is changed if products and reactant concentrations are changed

Answer 29

False, equilibirum constant can only change when temperature is changed

Question 30

T or F, deltaG is a fixed value for a given reaction, except under “standard conditions”

Answer 30

– False, delta G is not a fixed value for a given reaction, except under standard conditions

Question 31

What are the standard conditions in terms of temperature, concentration and pH

Answer 31

– Reactants and products at 1.0 M concentration

– 25degrees Celsius (298K, Absolute temp)

– pH = 7.0

Question 32

In coupling reactions what happens when both the first and second reactions are negative? what about the opposite where one is positive and one is negative?

Answer 32

you have to take first negative reaction and subtract second negative reaction; for positive and negative reaction one would add

Question 33

True or false. An unfavorable reaction can be coupled in order to allow for the overall reaction to be spontaneous

Answer 33

True