The roles of ATP in living cells and mechanisms of production part 1 Flashcards
what is metabolism
integrated set of enzymatic reactions comprising both anabolic and catabolic reactions
what is anabolism
synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP)
what is catabolism
breakdown of energy rich molecules to simpler ones (CO2 H20 NH3)
(energy released is captured as ATP and stored for later use in anabolic reactions)
how can anabolic and catabolic reactions be told apart
Anabolic – synthetic reactions (pathways end in genesis eg glycogenesis)
Catabolic – breakdown reactions (pathways end in lysis eg glycolysis)
why are bioenergetics important
Living cells and organism must perform work to stay alive
Energy required for motion (muscle contraction), transport (of ions/molecules across membranes), biosynthesis of essential metabolites), thermoregulation
why are storage forms of energy needed
Timing of processes doesn’t necessarily coincide with feeding times
why do cells require sources of free energy
Cells are isothermal systems so heat flow can’t be used as energy so free energy (energy available to perform work is acquired from nutrient molecules
what are important thermodynamic quantities
Gibbs free energy (G) – energy capable of doing work at constant temp and pressure
Enthalpy (H) – the heat content of reacting system
Entropy (S) – the randomness or disorder of a system
how goes G relate to H and S in cells
G=H-T S (change in all, ex T)
G of reaction – max energy that can be obtained from a reaction at a constant temp and pressure
H reflects the kinds and numbers of chemical bonds broken and formed (positive when energy absorbed by reaction)
S is formation of large complex molecules from smaller ones and vice versa (positive when randomness increases such as breaking up a larger molecule into smaller ones)
how does free energy change
A->B
Greater conc of B than A at equilibrium
Spontaneous or exergonic reaction, free energy defined as negative (G<0), energy liberated by reaction
Greater conc of A
Unfavourable or endergonic reaction, free energy positive, energy input required to start reaction
what are exergonic reactions
Products have less free energy than reactants and are more stable, formation downhill
change in G negative
catabolism
what are endergonic reactions
Products have more free energy than reactants so are less stable, uphill reaction
change in G positive
anabolism
how do endergonic reactions occur
Endergonic reaction coupled to exergonic to drive it forward, via common intermediate eg Glucose+Pi>G6P+H20 (exo) ATP+H2O>ADP+Pi (endo) overall ATP+Glucose>ADP+G6P change in G negative
what is ATP
Provides most of free energy required for endergonic reactions
ATP currency of cell, achieved by phosphate group transfer
How does ATP link to G
energy derived from oxidation of dietary fuels to generate ATP, energy conserved as ATP and transduced into useful work
How does ATP link to Mg2+
ATP/ADP Mg2+ complexes
ATP in cytosol is present as a complex with Mg2+
Mg2+ interacts with oxygens of triphosphate chain making it susceptible to cleavage in the phosphoryl transfer reactions
Mg2+ deficiency impairs virtually all metabolism
what is substrate level phosphorylation
Formation of ATP by phosphate group transfer from substrate to ADP
Require soluble enzymes and chemical intermediates
how is SLP different to Respiratory linked phosphorylation
resp linked phosphorylation involves membrane bound enzymes and transmembrane gradients of protons and require oxygen
what are enzymes
Biological catalysts that accelerate rate of chemical reactions by creating a new pathway with a lower activation energy
Does not influence G of reaction
what enzymes are important to know for SLP
Oxidoreductases - transfer of electrons
transferases - transfer of functional groups
what are coenzymes an cofactors
Cofactors – non protein molecules necessary for enzyme activity eg metal cations and coenzymes
what are coenzymes
Most are organic molecules derived from vitamins
Participate in enzymatic reactions
Cycle between oxidised and reduced forms
made of cosubstrates and prosthetic groups
CE and CS loose association to enzyme and diffuse between enzymes carrying e-
what are prosthetic groups
non protein cofactor that is covalently bound to enzyme so not released as part of reaction, acts as temporary e- store or intermediates
what are coenzymes and prosthetic groups
vitamin precursors
eg B2 > FAD/FMN or Niacin > NAD+
What do redox coenzymes and prosthetic groups do
Major redox coenzyme/prosthetic groups involved in transduction of energy from dietary foods to ATP – NAD+/FAD/FMN
Electrons are transferred from dietary material to these carriers – coenzymes reduced
In each case 2 e- transferred but H+ moved varies
Eg NAD+ reduced to NADH but FAD reduced to FADH2
what is Nicotinamide adenine dinucleotide
NAD+
NAD+ and NADP+ accept pairs of e- to form NADH or NADPH
Nicotinamide is functional part
NADH for ATP synthesis and NADPH for reductive biosynthesis
what happens to redox coenzymes after they’re used
re-oxidation
Recycling of NADH and FADH2 is via resp chain in mitochondria
Coupled to ATP synthesis – process of oxidative phosphorylation
where does cellular energy metabolism occur
Proteins/carbs/lipids to AA/glucose/FA and glycerol
glycolysis to pyruvate - cytosol
rest in mitochondria
Pyruvate to Acetyl-CoA - CAC-CO2- Oxidative phosphorylation
what is glycolysis
glucose to glucose-6-phosphate
to fructose-6-phosphate
to fructose-1,6-biphosphate
to dihydroxyacetone phosphate or glyceraldehyde-3-phosphate
what converts glucose to G6P
Hk
ATP to ADP
PRIMING REACTION
what converts G6P to F6P
isomerase
what converts F6P to F1,6BP
PFK-1
ATP to ADP
PRIMING REACTION
COMMITTED STEP
What converts F1,6BP to DHAP/G3P
Aldolase
DHAP to G3P interconverted by isomerase
G3P continues to glycolysis
what are payoff reactions
G3P 1,3 biphosphoglycerate 3 phosphoglycerate 2 phosphoglycerate phosphoenolpyruvate pyruvate
what steps of payoff reactions are SLP
3P to pyruvate
what converts G3P to 1,3BPG
GAPDH
NAD+ - NADH
what converts 1,3BPG to 3P
PGK
ADP to ATP
what converts 3P to 2P
Mutase
what converts 2P to PP
ENOLASE
what converts PP to pyruvate
PK
ADP to ATP
What key enzymes are involved in priming
Hexokinase - phosphorylation
PFK-1 - phosphorylation
Pyruvate kinase - phosphorylation
what is a summary of priming
investment of ATP at the hexokinase and PFK-1 reaction
uses2 ATP and produces to C3 molecules (interconvertible DHAP and GAP)
What is a summary of payoff
recovery of ATP by SLP in 1,3BPG and pyruvate reactions
generates 4 ATP and 2 NADH and various intermediates
what is pyruvate converted to
Pyruvate formed from glucose via glycolysis
Aerobic – oxidised and degraded to CO2 and H20
Hypoxic – reduced to lactate (lactate dehydrogenase, canoe reduced back with O2)
