BIOL 201 Lecture 1: L1 Jan 9 Energy in Cells 1
18 Feb 2019
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L1 Jan 9 Energy in Cells 1
ā¢ Orgs consume energy quality
o Living orgs convert high-quality energy into low-quality energy
o Plants do this by turning photons into chemical bonds
o Animals do this by turning energy from chemical bonds into heat and work
How do we define Energy Quality?
ā¢ Quality of energy depends on how much is āfreeā
o H=enthalpy=TOTAL energy
o G=free energy or available energy
o G=H ā unavailable energy
o S= entropy= disorder
o G=H- TS
Change in free energy determines if a process occurs spontaneously
ā¢ For isolated system-
o H=0
o S= positive value
o Therefore, G must be negative for a spontaneous process to occur
Free energy values are standardized:
ā¢ Standard free energies are additive- if have a seq of chem rxns (rxn A to rxn B to rxn C)
o Energy from going from A to C= energy from going A to B to C
ā¢ Releasing free energy is not always easy (related to transition states)
o Catalystās function is to lower the transition state so the rxn can occur
faster/easier
How do you make it over a transition state?
ā¢ Would in theory require a positive G value to get to transition state but we know total G
must be negative for spontaneous process
o Explanation- energy of molcs fluctuates over time
ā¢ Fluctuation comes from collision w other molcs (H2O, photons, etc)
o This causes shape distortion, the molc will change its configuration as energy is
gained/lost
o Also collides w neighbouring molcs and gives energy/gains energy from them
ā¢ Fluctuation allows the molc to reach its energy peak and it reaches threshold- pushing it
into its transition state
ā¢ This is why catalysts are able to lower energy of transition states
o Catalyst takes substrate and forces it into its transition state (peak energy) by
distorting the configuration
Document Summary
L1 jan 9 energy in cells 1: living orgs convert high-quality energy into low-quality energy, plants do this by turning photons into chemical bonds, animals do this by turning energy from chemical bonds into heat and work. How do we define energy quality: quality of energy depends on how much is free", h=enthalpy=total energy, g=free energy or available energy, g=h unavailable energy, s= entropy= disorder, g=h- ts. Change in free energy determines if a process occurs spontaneously: for isolated system, h=0, s= positive value, therefore, g must be negative for a spontaneous process to occur. How do these processes happen simultaneously: recall- free energies are additive, cells burn atp to drive unfavourable rxns, ex. Conversion of glutamic acid to glutamine is unfavourable (+g) but burning. Atp is a favourable (-g) with a g value that counteracts the +g of the rxn- this results in a net g value therefore rxn can happen.
