9 - energy, metabolism and enzymes Flashcards
what is energetics?
flow of energy and its charge from one form to another
what is metabolism
all chemical reactions in an organism that harness energy to do work
what is cellular metabolism
all chemical reactions in a cell that harness energy to perform essential functions: cell pumps and motors, muscular work, maintaining homeostasis, heat, growth and maintenance and repair.
what are activated carrier molecules?
all animal and plant cells are powered by energy stored in the chemical bonds or organic molecules, molecules that can be split to release energy:
- ATP - transfers Pi
- NADH and FADH2 - transfer a hydride (H-) and a proton (H+) (2 electrons)
what is stored bond energy used to do?
used to perform cellular work: hydrolysis of ATP to ADP.
what is the universal tendency to disorder?
stored energy is released (exergonic) to create disorder (entropy); ΔG –ive
effort/work is required (endergonic) to reverse disorder (enthalpy); ΔG +ive
ΔG = Gibbs free energy exchange: reversible work energy
what is the Gibbs free energy change determines by?
The Gibbs free energy change (ΔG) of a reaction is determined by:
The difference in free energy level between reactant (A) and product (B)
what happens if ΔG° is negative?
the reaction is exergonic energy is released. the reaction goes forward spontaneously.
what happens if ΔG° is positive
the reaction is endergonic it requires energy input. the reaction does not go forward spontaneously.
what happens if ΔG° is zero?
the reaction goes neither forward nor backward spontaneously: A (reactant) and B (product) have reached equilibrium.
what is activation energy?
to make molecules react together, often additional energy is needed to overcome an energy barrier
the amount of energy needed to overcome this is the activation energy or Ea
reaction rate depends on size of Ea
when is a reaction exergonic?
the products contain less energy than the reactants
ΔG° is -ve and the reaction is spontaneous
when is a reaction endergonic?
the products contain more energy than the reactants i.e. ΔG° is +ve. the reaction is not spontaneous.
what are coupled reactions?
the energy released from one reaction can be used to drive another unfavourable reaction
what is reaction rate determined by?
- substrate/enzyme concentration
- temperature and pH
- enzyme modifications, inhibitors and activators.
