Lecture 4

Question 1

What is thermodynamics?

Answer 1

• the energy of systems

Question 2

What is metabolism

Answer 2

• the sum of all chemical reactions performed by a living organism

Question 3

Catabolic pathway

Answer 3

• breaks down molecules into smaller molecules which can be used to generate energy and chemical building blocks

Question 4

Anabolic pathways

Answer 4

• uses energy provided by catabolism to drive the synthesis of other molecules

Question 5

What is the first law of thermodynamics

Answer 5

• the total amount of energy in the universe remains constant, although the form of energy may change
• cells convert energy from one form to another
• example: electromagnetic energy to chemical bond energy

Question 6

What is the second law of thermodynamics

Answer 6

• the tendency of nature is toward ever-greater disorder in the universe

Question 7

What is entropy

Answer 7

• a measure of a systems disorder

Question 8

How do cells not defy the second law of thermodynamics

Answer 8

• although cells can cause molecules within it to be very ordered, it releases heat into the surroundings (heat is energy in its most disordered form)

Question 9

What is photosynthesis and cellular respiration?

Answer 9

• photosynthesis is the conversion of electromagnetic energy into chemical bond energy
• cellular respiration is the process of obtaining energy from organic molecules resulting in the production of H2O and CO2
• the two processes are complementary

Question 10

Oxidation

Answer 10

the removal of an electron from an atom (increasing the charge)

Question 11

Reduction

Answer 11

the addition of an electron from an atom (reducing the charge)

Question 12

Oxidation and reduction reactions always occur _______________

Answer 12

simultaneously

Question 13

If you were trying to obtain energy from a molecule, would you rather use methane or CO2?

Answer 13

Methane because carbon is more electronegative than hydrogen so it is easier to steal the electrons, methane is the most reduced and CO2 is the most oxidized

Question 14

What is free energy and how is it expressed?

Answer 14

• the energy that can be harnessed to do work and drive chemical reactions
• it is expressed as “G” denoted as “∆G”

Question 15

What happens when “∆G” is negative

Answer 15

• means the reaction is spontaneous/exergonic, +G means the reactions is non-spontaneous/endergonic

Question 16

How might an unfavourable reaction occur

Answer 16

• unfavourable reaction can occur if they are coupled to a favourable one
• the net free energy of the coupled reaction must show a decrease in energy (overall G must be negative)

Question 17

What is the standard free energy change?

Answer 17

∆G°→is the ∆G of a reaction calculated under specific conditions
→makes it possible to compare the energetics of different reactions

Question 18

what is activation energy

Answer 18

• the energy that must be acquired to undergo a chemical reaction

Question 19

what is a catalyst

Answer 19

• a substance that lowers the activation energy of a reaction

Question 20

what is an enzyme

Answer 20

• it is a biological catalyst
• it speeds up the rate of a reaction by lowering the activation energy
• it is not consumed in the process
• highly specific in terms of substrate and in terms of reaction

Question 21

Does an enzyme alter ∆G

Answer 21

no it does not!

Question 22

Why are enzymes important for humans?

Answer 22

• because they allow reactions to occur in our bodies that normally take place really slowly

Question 23

What is ∆G dependent on

Answer 23

∆G is dependent on the concentrations of substrates and products

Question 24

are cells ever at thermodynamic equilibrium?

Answer 24

• no unless they are dead because living cells are constantly exchanging material with their environment
• and cells often establish disequilibrium because they siphon off products from one reaction to participate in another reaction

Question 25

What is the equilibrium constant (K)?

Answer 25

• the ratio of substrates and products when the rates of the forward and reverse reactions are equal
• it is directly proportional to ∆G°
  K= [Products]/[Reactants]
  ∆G=∆G⁰+ RTlnK

Question 26

When k is less than 1, equal to 1, or more than 1 what happens

Answer 26

• K>1: ∆G is negative but the reaction will proceed forward
• K= 1: ∆G is zero and reaction is at equilibrium
• K<1: ∆G is positive and reaction will proceed in reverse

Question 27

If two reactants bound noncovalently to form the product of a reaction, would you expect the free energy change to be positive or negative?

Answer 27

Negative→when you are forming bonds, you are releasing energy