Enzyme controlled energy metabolism and glycolysis Flashcards
Processes in the body that require energy [4]
Muscle contraction- motion.
Transport of ions/molecules across membranes.
Biosynthesis of essential metabolites.
Thermoregulation
Free energy
Energy available to perform work- cells require this as they are isothermal.
Cells cannot use heat energy as a source of energy.
Gibbs free energy=
Change in enthalpy- ( change in entropy x temperature)
Exergonic reaction
Also a spontaneous reaction- catabolism
When the products exceed the reactants at equilibrium.
Change in free energy < 0, energy is released when the reaction occurs.
Products have less free energy than reactants - so are more stable
Endergonic reaction
Also an unfavourable reaction- anabolism
When the reactants exceed the products at equilibrium.
Change in free energy > 0, energy has to be taken from the environment for reaction to occur.
Products have more free energy than reactants.
Coupling reactions
Energy liberated from exergonic reactions can be used to drive forward endergonic reactions
- through a common intermediate.
Example: phosphorylation of glucose is endergonic and uses energy released from the hydrolysis of ATP (exergonic)- using phosphate H20 and phosphate as a common intermediate
Phosphate group transfer
The method of hydrolysing ATP to ADP by forming an intermediate with a phosphate group.
Phosphate is later then released into solution.
ATP is not simply hydrolysed but instead the phosphate group is temporarily transferred.
Mg2+ complexes
Mg2+ forms complex with ATP in the cytosol.
Mg2+ interacts with oxygens on the triphosphate chain.
- This allows the chain to be susceptible to cleavage from phosphate group transfer.
Substrate level phosphorylation
Phosphate group transfer from another substrate to ADP to form ATP.
Uses soluble enzymes and chemical intermediates.
Oxidoreductases
Enzymes that transfer electrons- can oxidise or reduce substrates.
Examples:
- Oxidases
- Reductases
- Peroxidases
Transferases
Enzymes that transfer functional groups
Co-enzymes
Non-protein cofactors.
Derived from vitamins.
Have a loose association with their enzyme and carry electrons between enzymes.
Regenerated to maintained cellular concentrations.
Example: NAD+
Prosthetic groups
Non-protein cofactors that are permanently associated with their enzymes- covalently bound
Temporarily stores electrons
Example: FAD or FMN
FAD
Prosthetic group derived from from B2- riboflavin
Receives electrons from dietary material to be reduced.
- Receives 2 electrons and 2 protons to form FADH2
- Reoxised in the respiratory chain during oxidative phosphorylation.
FMN
Prosthetic group derived from from B2- riboflavin
NAD+
Co-enzyme derived from vitamin niacin- - Functional group is nicotinamide
Receives electrons from dietary material to be reduced.
- Receives 2 electrons (hydride ion) and 1 proton
- Forms NADH
NADH is reoxidised in oxidative phosphorylation, via the respiratory chain or anaerobic respiration.
