Lecture 4 Flashcards
What is thermodynamics?
- the energy of systems
What is metabolism
- the sum of all chemical reactions performed by a living organism
Catabolic pathway
- breaks down molecules into smaller molecules which can be used to generate energy and chemical building blocks
Anabolic pathways
- uses energy provided by catabolism to drive the synthesis of other molecules
What is the first law of thermodynamics
- 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
What is the second law of thermodynamics
- the tendency of nature is toward ever-greater disorder in the universe
What is entropy
- a measure of a systems disorder
How do cells not defy the second law of thermodynamics
- 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)
What is photosynthesis and cellular respiration?
- 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
Oxidation
the removal of an electron from an atom (increasing the charge)
Reduction
the addition of an electron from an atom (reducing the charge)
Oxidation and reduction reactions always occur _______________
simultaneously
If you were trying to obtain energy from a molecule, would you rather use methane or CO2?
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
What is free energy and how is it expressed?
- the energy that can be harnessed to do work and drive chemical reactions
- it is expressed as “G” denoted as “∆G”
What happens when “∆G” is negative
- means the reaction is spontaneous/exergonic, +G means the reactions is non-spontaneous/endergonic
How might an unfavourable reaction occur
- 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)
What is the standard free energy change?
∆G°→is the ∆G of a reaction calculated under specific conditions
→makes it possible to compare the energetics of different reactions
what is activation energy
- the energy that must be acquired to undergo a chemical reaction
what is a catalyst
- a substance that lowers the activation energy of a reaction
what is an enzyme
- 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
Does an enzyme alter ∆G
no it does not!
Why are enzymes important for humans?
- because they allow reactions to occur in our bodies that normally take place really slowly
What is ∆G dependent on
∆G is dependent on the concentrations of substrates and products
are cells ever at thermodynamic equilibrium?
- 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
What is the equilibrium constant (K)?
- 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
When k is less than 1, equal to 1, or more than 1 what happens
- 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
If two reactants bound noncovalently to form the product of a reaction, would you expect the free energy change to be positive or negative?
Negative→when you are forming bonds, you are releasing energy
