Bioenergetics Flashcards
Define Bioenergetics
Quantitative study of energy transformations and exchanges upon which all life depends
Study of the nature and function of the chemical processes underlying energy transformation and exchange
What does it mean by Biological systems being open?
They can absorb energy from, and give energy back to their surroundings
What is the use of the ATP cycle?
Linking energy release and utilisation within cells
What is the first step in the ATP cycle?
Energy sources enter such as stored nutrients, ingested foods and solar photons
ADP converted to ATP
What is the second step of ATP cycle
Catabolic reactions
Exergonic: free energy released from stores converted to ATP
What is the third step of ATP cycle
Heat energy dissipated to surroundings
What is the forth step of ATP cycle?
Anabolic reactions: Endergonic: Free energy stored in ATP released to maintain biological systems
ATP converted to ADP
What is the final step of ATP cycle
Complex biomolecules cellular work (such as mechanicla osmotic) released
Define free energy
The portion of the energy of a system capable of doing work
Results from the difference in atoms and bonds present in reactants and products
Define enthalpy
Living animals can’t use heat energy to do work
Essentially Isothermal
Temperature throughout the system is uniform
Enthalpy change also has a disorder component (entropy)
Unavailable for work in biological systems
What does biological systems use to drive living processes?
Chemical energy
Define Gibbs free energy (G)
Chemical energy avaible for work
G is related to enthalpy change and entropy
Define Exergonic reactions
Have Negative Delta G
Products have less free energy than reactants
Free energy released is available for work
Reactions will be spontaneous
Define Endergonic reactions
Energy is absorbed or entropy decreases
Has positive Delta G
Products have more free energy than reactants
Input of free energy is required
Reactions will not process spontaneously
Define spontaneous in relation to Endergonic and exergonic
Doesn’t mean instantaneous
Delta G is a measure of whether a reaction is spontaneous
Does not predict rate of reaction or stability of reactants
When is a reaction spontaneous?
Large, negative free energy change occurs
ATP is very stable
Only breaks down when catalysis is present to reach activation energy
Explain large negative free energy change on a molecular level
ATP as an example
Products are more stable than reactants
Electrostatic repulsion requires energy to be removed
Phosphate and ADP seperate nicely through hydrolysis
Energy released with addition release of free energy because product is rearranged
Ionisation used to get product into more stable form
Define Resonance stabilisation
Pascal negative charge on all the oxygens
Free energy change is due to?
The sum of all atoms and bonds present in reactants and products
Free energy of high energy phosphates not due to hydrolysis alone, what else?
Type of bonding reactants and products is also important
Free energy of hydrolysis is large because keto form of pyruvate is more stable
Free energy of hydrolysis is large because of resonance stabilisation
What is ATP hydrolysis like in free solution?
Loss of free energy of hydrolysis as heat
ATP is only a useful transducer of free energy because free energy of hydrolysis is coupled via group transfer
Explain coupled reactions
Share a common intermediate therefore can link
The reactions can be coupled because they have phosphate as a common intermediate
Often involved activated enzyme intermediates
Phosphorylation of the enzyme provides sufficient energy for group transfer
Why is ATP hydrolysis used in coupled reactions?
Couples to another reaction makes the overall reaction energetically favorable
What can we predict from Delta G
The direction in which a reaction will proceed
The equilibrium position
The amount of work a chemical reaction can theoretically perform
How are Delta G and Equilibrium constant of a reaction related?
For reactions of this type: A + B C + D
Composition of reactants and products in a system will change constantly until equilibrium is reached
Rates of the forward and reverse reactions are the same as equilibrium
No net change in [reactant] and [product] at equilibrium
Ratio of [product] and [reactant] at equilibrium determine equilibrium constant
What is the 1st law of thermodynamics?
The energy of the universe is constant: Energy may change form or be transported from one region to another but it cannot be created or destroyed
What is the 2nd law of thermodynamics?
In all natural processes, the entropy of the universe increases:
Every energy transfer or transduction increases the entropy of the universe
Increase in entropy need not be within the observed system
