Molecular Energy Transformations: Thermodynamics

Question 1

What is a biological system?

Answer 1

Anything of interest (biochemical reactions, cells, organisms, ecosystems, etc…) that interacts with its surroundings and the rest of the universe.

Question 2

Describe the 3 types of systems?

Answer 2

• Isolated system: does not exchange matter or energy with its surroundings.
• Closed system: exchanges energy with its surroundings.
• Open system: Exchanges both energy and matter with its surroundings.

Question 3

What is energy?

Answer 3

The ability to cause change.

Question 4

What is work?

Answer 4

The change that requires energy.

Question 5

What is the first law of thermodynamics?

Answer 5

• Energy cannot be created or destroyed.

But it can:
- change location (outside a cell to inside).
- change into different forms (potential to kinetic).
- all energy that enters a system must come from the surroundings.

Question 6

What is potential and kinetic energy?

Answer 6

Potential energy: stored energy due to position (energy at rest).
Kinetic energy: energy of motion/change (energy doing work)

Question 7

What has more potential energy (Ep), an electron closer to a nucleus or further away? Why?

Answer 7

An electron close to a nucleus has smaller Ep, an electron far from a nucleus has larger Ep.

This is because when an electron moves to a higher energy level, it has the potential to fall back down to a lower energy level again. But when its at a low energy level, it can’t move lower so it has little Ep.

Question 8

What type of chemical bond (non-polar covalent, polar covalent or ionic) has more Ep? Why? Give a full explanation.

Answer 8

The amount of potential energy within a molecule depends on the arrangement of electrons in its chemical bonds.

• Molecules with non-polar covalent bonds have more Ep.
• This is because the non-polar covalent bond holds the electrons in the middle of the bond and it can fall further towards either electron.

Question 9

What is an electrochemical gradient? Is the potential energy higher or lower when one side has a higher concentration than the other?

Answer 9

• An electrochemical gradient is a difference in ion or solute concentration across a membrane.
• It is higher, since the ions or solutes have not yet traveled across the membrane.

Question 10

What is enthalpy?

Answer 10

The sum of Ek (kenetic energy) and Ep (potential energy)

Question 11

What happens when work occurs? What does Delta H represent?

Answer 11

• Something changes (a chemical reaction changes reactants to products).
• New system has a different enthalpy.
• Delta H represents the change before a reaction to after a reaction
• Measured as the amount of heat released or absorbed to the surroundings
• If heat is released, delta H is negative, if heat is absorbed, delta H is positive

Question 12

What does exothermic mean?

Answer 12

The products have less enthalpy than the reactants. ( - (number) Kj/mol^-1)

Question 13

What does endothermic mean?

Answer 13

The products have more enthalpy than the reactants. ( + (number) Kj/mol^-1)

Question 14

Define spontaneous vs nonspontaneous. Are spontaneous reactions instantaneous?

Answer 14

Spontaneous: A reaction that can occur under corrent conditions. (just bcause they can happen, does not mean they are NOT instantaneous)!!!!

Nonspontaneous: A reaction that can not occur under current conditions.

Question 15

What are some important “current conditions” to be aware of? Which ones are usually manipulated in biology?

Answer 15

Not typically manipulated in biology:
- Temperature
- pH
- Atmospheric Pressure

Manipulated:
- Concentration of reactants or [reactants]
- concentration of products or [products]

Question 16

Does enthalpy (Delta H) determine if a reaction is spontaneous?

Answer 16

NO it does not!!!!

Question 17

What is entropy? What happens when work occurs?

Answer 17

entropy is a measure of how dispersed the energy in the surrounding system is.

When work occurs, the new system/surroundings have different entropy (the dispersion of energy in the universe changes)

Question 18

What does ‘Delta S’ represent? What does a positive or negative delta S represent?

Answer 18

• The change in energy before a reaction to after a reaction. Measured as the degree to which energy dispersal has changed.
• Positive delta S: energy has become more dispersed
• Negative delta S: energy has become less dispersed

Question 19

What is the second law of thermodynamics?

Answer 19

Energy in the universe must always increase. Every transfer or transformation of energy must increase total entropy.

Question 20

Does entropy determine if a reaction is spontaneous?

Answer 20

Yes it does.

Question 21

What is the equation to calculate Delta S Total? Why does it work?

Answer 21

• The equation to calculate delta S total = Delta S (system) + Delta S (surroundings).
• This is because entropy considers the system and surroundings. This means that the entropy of the system can decrease if the entropy of the surrounding increases to a greater degree.

Question 22

What is free energy and how is it Represented?

Answer 22

Free energy is represented by (G) and is a measure of the energy in a system that is free to do work.

Question 23

When does work occur? What is this changed represented by? (all in refrence to G)

Answer 23

• Work occurs when the reactants have more free energy than the products.
• The change in free energy before a reaction to after a reaction is measured as the amount of energy that was used to make the change. This is Delta G

Question 24

What does a positive or negative delta G represent?

Answer 24

Negative delta G: energy is available.
Positive Delta G: energy is not available.

Question 25

What does exergonic mean?

Answer 25

• Products will have less energy than the reactants. Free energy is released and the reaction is spontaneous.
• This means that delta G will be negative.

Question 26

What does endergonic mean?

Answer 26

• Products will have more energy than the reactants. Free energy is gained and the reaction is not spontaneous.
• this means delta G is positive.

-THIS CANNOT HAPPEN EVER IN ANY WORLD

Question 27

What is the relationship between Delta G and Delta S (total): The equation?

Answer 27

• Delta G = -t (kelvin) * delta S (total): there is enough energy to change the system and increase the energy in the universe.

Question 28

What is the relationship between Delta G, Delta H and Delta S (what are all the equations)?

Answer 28

Delta G = -t (kelvin) * delta S (total)
or
Delta G = -t (kelvin) * Delta S (surrounding) + (-t * Delta S (system))
or
Delta G = (Delta H) - t (kelvin) * Delta S (system)

Question 29

What is chemical equilibrium? When does it occur?

Answer 29

• is it when: Regardless of the starting concentrations of the reactants and products, they do not go to completion.
• it occurs when: the rate of the forward and reverse reactions are equal.

at equilibrium: Delta G = 0 and therefore No free energy change

Question 30

What is the relationship between free energy change and chemical equilibrium?

Answer 30

• As a spontaneous reaction proceeds, the conditions change. [reactants] decrease and [products] increase. Delta G will change until it equals zero, and chemical equilibrium is reached. for the reaction to proceed, the conditions must change: add or remove reactants or products.
• There is now not enough free energy in a system to allow further overall change.

Question 31

define metabolism, also refer to catabolism and anabolism.

Answer 31

The sum of all reactions in the cell is called metabolism.

Breaking down complex molecules into smaller molecules is called: Catabolism

Building up complex molecules is called: anabolism

Question 32

What are biochemical pathways? What is an example of a biochemical pathway in metabolism?

Answer 32

• Biochemical pathways are a series of interconnected bio-chemical reactions.
• When you eat, your body will break down energy rich molecules into energy poor molecules (catabolism). The using some of the building blocks and chemical energy, aanbolism occurs. Molecules are then built up into larger molecules like proteins.

Question 33

What is a connected reaction?

Answer 33

A connected reaction is when the product of the first reaction is the substrate for the second reaction.

Question 34

Are all reactions exergonic?

Answer 34

Yes, an endergonic reaction cannot happen unless you change the conditions.

Question 35

Are nucleotides high Ep molecules?

Answer 35

Yes, they are.

Question 36

Why is ATP so negatively charged? What seperates ATP from ADP?

Answer 36

• ATP has a total negative charge given to them by the triphosphate, specifically the end one thats the most negative.
• ATP has 3 phosphate groups attached to it, ADP only has 2.

Question 37

What is ATP hydrolysis?

Answer 37

ATP + H2O –> ADP +Pi (DELTA G is NEGATIVE)

Several bonds are broken and new bonds are formed when ATP is hydrolized.

G of new bonds is less than G of old bonds.

Question 38

Give me the reactions that produce Glucose-6-P and the steps:

Answer 38

Glucose becomes phosphorylayted: Glucose + P –> Glucose-6-P + H2O

ATP is hydrolized: ATP + H2O –> ADP + Pi

Question 39

What are coupeled reactions drawn with typically? draw the coupeled reaction with Glucose + ATP –> Glucose-6-P + ADP

Answer 39

They are drawn with arrows curving and touching the reaction.