Bioenergetics Flashcards
What is the equilibrium constant?
Kq
- describes the composition of the reaction mixture at equilibrium
Kq = concentration of products / concentration of reactants
to the power of their stoichiometry
What does Gibbs free energy tell us?
what direction the reaction needs to go in to reach equilibrium
does not give information about rate
What are bioenergetics useful for?
describing continuous conditions where reactions occur spontaneously
helps understand
- structure macromolecules
- how membrane transport processes occur
- how metabolic processes provide energy for the cell
What are the types of biochemical reactions?
endergonic
- positive gibbs free energy
- never spontaneous
example - condensation
exergonic
- negative gibbs free energy
- always spontaneous
example - hydrolysis
Why is ATP a good source of energy?
has adenosine (nucleoside = sugar + base) and three phosphate groups
energy is provided with each phosphate group removed
How is ATP hydrolyses to provide energy?
1 - hydrolytic cleavage of the gamma phosphate anhydride group = relieves electrostatic repulsion in ATP
2 - phosphate formed is stabilised by resonance structures
3 - ADP products immediately ionises, releasing a proton into the medium
4 - ATP has small solvation compared to solvation energies of ADP, phosphate ion and proton
What are coupled reactions?
chemical reaction with a common intermediate where energy is transferred from one reaction to another
free energy from the first reaction is sued to drive the second reaction forward
What is an example of a coupled reaction?
hydrolysis of ATP (addition of water) releases ADP and a phosphate ion
this reaction which has higher (more negative) gibbs free energy is used to drive the reaction of phosphorylating glucose
phosphorylation of glucose forms glucose 6-phosphate and water
What is oxidation?
loss of electrons
loss of hydrogen
gain of oxygen
What is reduction?
gain of electrons
gain of hydrogen
loss of oxygen
What are oxidising and reducing agents?
oxidising agents are reduced and cause oxidation of another substance
reducing agents are oxidised and cause reduction of another substance
What are coenzymes?
organic molecules that can function as electrons carriers
- transfers electrons needed for redox reactions
What is an example of coenzymes?
NADH (NAD+) and NADPH (NADP+)
= derived from vitamins, are water soluble cofactors
- can carry electrons back and forth between enzymes easily = reversible
- oxidising agent
undergo reversible reductions of the nicotinamide ring
Why is NAD called an oxidoreductase?
also known as dehydrogenase or reductases
- catalyses the transfers of electrons from one molecule to another
