M2 L7 Flashcards
Energy transactions, cofactors, ATP
what is the difference between catabolic and anabolic reactions
catabolic reaction (Degradation):
Fuel (carbohydrates, fats) → CO2 + H2O + useful energy
anabolic reaction (Biosynthesis):
Useful energy + simple precursors → Complex molecules
Catabolism involves degradation – breaking larger molecules into smaller, simpler ones,
and releasing useful energy in the process
Anabolism involves biosynthesis – making larger, more complex molecules from simpler
precursors.
Explain in simple thermodynamic terms why metabolic reactions occur in pathways
A metabolic pathway is a series of interconnected biochemical reactions that convert a substrate molecule(s) through a series of metabolic intermediates, eventually yielding a final product(s)
Explain why ATP can be used as a source of energy to drive reactions and processes
ATP links energy-producing and energy-utilizing systems
Describe briefly the functions of NAD+ and FAD
FAD: Insoluble- always bound to enzymes
it can accept two electrons and two protons
NAD+: These cofactors are soluble
can accept two electrons and one proton
Explain what is meant by reducing equivalent and why these are important in metabolic reactions and pathways
Protons and electrons that are released from substrates during catabolism
The transfer of reducing equivalents in biochemical reactions conserves energy
Describe the role of Coenzyme A
It is a central role in many metabolic reactions, its vitamin component is pantothenic acid (B5) reactive group is thiol (store of free energy) Carries acyl groups
Coenzyme A serves as an acyl group donor and acceptor
It’s a source of free-energy that can be used in coupled reactions
Explain what is meant by an endergonic and an exergonic reaction
If Keq is less than 1, ΔG0’ will be positive reaction is endergonic (requires energy, absorbs energy in the form of work, decrease in entropy)
If Keq is more than 1, ΔG0’ will be negative reaction is exergonic (change in free energy is negative, increase in entropy)
Use ΔGo values to predict the direction of a metabolic reaction
If ΔG is 0, the process is a equilibrium
If ΔG is negative, the process proceeds to equilibrium
If ΔG is positive, the process proceeds in the reverse direction
where is free energy derived from in the enviroment?
Phototrophs (plants) obtain free energy by trapping sunlight
Chemotrophs (animals) obtain free energy through the oxidation of foodstuffs
how do you release the energy in ATP?
The water molecule attacks the + center of the final phosphate group (hydrophilic attack)
Forms inorganic phosphate (broken off) Turns into ADP (adenosine diphosphate)
it repeats and it created AMP (Adenosine monophosphate)
It repeats and all that is left is adenosine.
Why can ATP be used to provide energy for “work” processes?
ATP has two ‘high energy phosphate ester bonds’ that can provide energy on hydrolysis. They are coupled to reactions which release energy
How is energy from catabolism of fuels used in the biosynthetic reactions?
It is transferred to intermediates using coupled reactions. Intermediates or products from catabolism can be used in more coupled reactions in biosynthetic reactions.
explain how free energy is conserved in pathways
When large changes in free energy occur this free energy is conserved in cofactors (NADH, NADPH or FADH2). These reduced cofactors can be used directly in another pathway to provide reducing power. So the energy conserved in one pathway (catabolic) can be used in a second pathway (anabolic).
