Lecture Focus Questions; Energy

Question 1

What is Energy?

Answer 1

-It is the capacity to do work/ exert a force on an object

Question 2

What is Potential Energy?

Answer 2

-Energy stored for later use

Question 3

What are the 2 different qualities of Energy?

Answer 3

• Free energy= available to due work

- Entropy=Energy lost in disordered states

Question 4

What different forms of energy are present in Biological systems?

Answer 4

-Electromagnetic energy AKA radiant
-Chemical energy
(we occasionally see thermal & electrical)

Question 5

What is Entropy?

Answer 5

• It is derived from the 2nd law of thermodynamics
• It is described as the “measure of disorder” of the number of possible atomic arrangments that give rise to the same overall state
• SO the more possible arrangments the more entropy
• Entropy is always increasing in isolated systems

Question 6

What does the 2nd Law of Thermodynamics state?

Answer 6

• It states that energy transactions cannot be 100% efficient
• SO the energy that is wasted is unusable & disordered due to an increase in Entropy

Question 7

What concepts are applicable for all systems?

Answer 7

-The concepts of free energy which can be used in isolated systems or open systems like living systems

Question 8

What equation is used to calculate ▲G & what do the variables mean?

Answer 8

▲G=▲H -T▲S
with H being Enthalpy (total energy)
T for temperature
S for Entropy

Question 9

What does it mean when a reaction is Spontaneous?

Answer 9

-It is thermodynamically favored to go in the forward direction from reactants to products which have a negative ▲G= Exergonic

Question 10

What is the difference between Exergonic reactions & Endogornic reactions?

Answer 10

• Exergonic reactions are spontaneous, negative & release negative▲G
• Endergonic reactions are not spontaneous, positive ▲G & consume energy only if energy is provided

Question 11

What is a key characteristic of chemical reactions?

Answer 11

-They are reversible

Question 12

How can we predict the direction of a chemical reaction?

Answer 12

• We can do it based on thermodynamics
• SO if a reaction has a negative ▲G (▲G <0) then the reaction will go forward w/ the products predominating
• If a reaction has positive ▲G (▲G>0) then the reaction doesn’t happen & reactants predominate at equilibrium

Question 13

How is life on earth similar to a refrigerator?

Answer 13

• They are both open systems that can create order w/ input of energy= reducing entropy
• Both still obey the 2nd law of thermodynamics

Question 14

What is ATP?

Answer 14

• It is an RNA nucleotide that is used as the energy currency of cells
• It doesn’t decay & it is a high energy molecule

Question 15

What does the Hydrolysis of ATP generate?

Answer 15

• It generates ADP and Pi

- It is also very exergonic which releases 7.3kcal /mol of free energy

Question 16

How is ATP used in coupled reactions?

Answer 16

-When ATP is hydrolyzed, the energy released is coupled to drive endergonic reactions

Question 17

Since the hydrolysis of ATP is an exergonic reaction, how can we have ATP at all?

Answer 17

• The hydrolysis of ATP is spontaneous but it will not occur rapidly bc there is a substantial energy barrier that must be overcome
• and that the ATP molecules & its bonds are stable

Question 18

How do cells stay alive?

Answer 18

-They do it by continually synthesizing new molecules but they need energy to carry out the endergonic synthesis

Question 19

What is the Activation Energy Barrier?

Answer 19

-It is the energy required to convert one molecule to another that ALL STABLE MOLECULES NEED

Question 20

What is Kinetics?

Answer 20

-It is the rate of a reaction

Question 21

What is the difference between Thermodynamics & Kinetics?

Answer 21

• Thermodynamics is when a reaction is spontaneous or not which can be fast or slow
• Kinetics is how fast a reaction is

Question 22

What is the difference between reactions with large activation energy barriers & low activation energy barrier?

Answer 22

• The reactions with the high activation energy barrier will occur slower
• While the reaction with the low activation energy barrier will occur faster

Question 23

What is Enzymes?

Answer 23

• They are biological catalysts to speed up reactions by lowering the activation energy barrier without affecting the energy of the reacting molecules
• They DO NOT CHANGE the spontaneity, thermodynamics, or relative predominance of reactants & products

Question 24

What kinds of molecules are Enzymes?

Answer 24

-Most are proteins w/ a folded 3D structure while some enzymes are RNA molcules

Question 25

What 3 mechs do Enzymes use to do their job?

Answer 25

• Orient molecules to react better
• They can stabilize the transition rate (highest energy point)
• They can also promote an alternative reaction w/ less activation energy