Couples Reactions and Metabolic Pathways Flashcards
thermodynamics
set of principles that apply to all physical and biological processes and govern conditions under which they can occur
1st law
total amount of energy within a system and its surroundings is constant
2nd law
total entropy (level of disorder) of a system and its surroundings always increases
3rd law
entropy of a system approaches a constant value when its temp reaches 0
system
whatever part of the universe we are interested in
closed system- cannot exchange matter across boundaries
open system- can pass matter back and forth across boundaries (cells)
surroundings- everything that surrounds the system (rest of universe)
enthalpy (H)
enthalpy (H) = E + PV
energy at constant pressure and volume
thermodynamic quantity equivalent to the total heat content of a system
It is equal to the internal energy of the system plus the product of pressure and volume.
∆H and ∆E are similar in solid and liquid
heat released or absorbed by a system at constant volume is equal to total internal energy
exo- release of heat (energy)
endo- heat (energy) absorbed
entropy (S)
refers to level of disorder in a system
how energy is distributed in a system
low entropy- organised
high entropy- disorganised
entropy always increases spontaneously
gibbs free energy
tells us if a process will occur on its own (spontaneous or not)
expressed as ∆G
∆ G° = ∆H - T ∆S
G considers for both enthalpy and entropy
∆G < 0 = a spontaneous process (exergonic)
∆G > 0 = not a spontaneous process (endergonic)
all biochemical reactions must result in a loss of free energy/increased entropy and therefore be exergonic (- ΔG).
spontaneous or not
enthalpy- exothermic= ∆H < 0 endothermic= ∆H > 0
entropy- disordered= ∆S > 0 ordered= ∆S < 0
exothermic + disorded= -∆G (neg) spontaneous
endothermic + disorded- spontaneous at high temp
exothermic + ordered- spontaneous at low temp
endothermic + ordered= +∆G- non spotaneous
thermodynamic changes
low entropy (organised) to high entropy (disorganised) occurs when ∆S >0 (increased)
high enthalpy to low enthalpy
∆H <0 (has decreased eg exothermic)
example is bomb going off
∆G < 0 LOSS OF FREE (AVAILABLE) ENERGY
rules of ∆G
reaction will occur spontaneously if ∆G <0
reaction cannot occur spontaneosly if ∆G>0- energy input is required
∆G=0 at equilibrium
∆G reaction depends on free energy of the reactions and products and is independent f the path it takes to get there
∆G provides no info about rate of reaction
coupled reactions
reaction cannot occur spotnaneously if ∆G is >0- energy input is required
overall free energy change ∆G for a coupled reaction is equal to the sum of its individual reactions
coupled reactions- energy favourability
energetically favourable- free energy of Y is greater than that of X
during reaction of Y to X
free energy (∆G) is <0 and disorder of universe increases
spontaneous
energetically unfavourable
reaction of X to Y
free energy (∆G) is >0 and universe would become more ordered
only occurs if coupled with energetically favourable reaction
activated carriers
if ∆G is >0 energy must be stored eg after being released from oxidation
stored in molecules called activated carriers as chemical group or electrons
energy is then used for endergonic reactions or other cell activities
ATP is most widely used and important activated carrier molecules
obtaining energy
cells obtain energy through the oxidation of organic molecules
energy is stored in covalent bonds of these organic molecules
individual anabolic and catabolic reactions which enable us to obtain energy from organic molcules is called metabolism
fuel oxidation
oxidation- removal/ loss of electrons
reduction- gain of electrons
electrons are never actually lost- one molecule oxidised, another must be reduced
(electrons are normally followed by hydrogen- less C-H bonds indicated oxidation)
glycolysis
oxidation of sugars
consists of 10 reactions
atp hydrolysed in reactions 1 and 3; phosphorylates sugar, couple reaction to make it energetically favourable
glycolysis doesnt involved oxygen (involved oxidation + NAD is reduced)
atp is generated in reaction 7 and 10
(energy investment phase - 1+ 3 and energy generation phase 7+ 10)
lactate
glycolysis may become 11 reaction pathway when lactate is produced from pyruvate
when no o2 is available to act as electron acceptor, nadh passes electrons to pyruvate to form lactate
normal circumstances- pyruvate moves into mitochondria where it is decarboxylated to form acetyl coA
β-Oxidation
fatty acids converted to fatty acyl coA and transported to mitochondria
fatty acyl coA enters β-Oxidation
β-Oxidation = 4 enzymatic reactions which reduces number of carbons on fatty acyl coA
produces acetyl coA, 1xNADH and 1 FADH2
cycle continues until all carbons are removed and fatty acid is degraded
tca cycle
results in complete oxidation of c atoms on acetyl coA
acetyl coA (2C) is transferred to 4C oxaloacetate to form citric acid (6C)
series of 8 reactions (4 oxidation) regenerate oxaloacetate
energy released - 3x NADH, 1xFADH2, 1XGTP
