Biochemistry Flashcards
What is meant by the term bioenergetics? (2)
Transformation and flow of energy within biological systems, and their environment.
Concerned with the initial and final energy states of reactants, not the mechanism or kinetics
What is the significance of “bioenergetics” to us?
2 possible answers
1) Study of how such energy flows, transforms and harnessed.
2) Processes by which the body meets energy demands e.g. digestion & other metabolism.
What is thermodynamics?
laws & principles describing the flow and interchanges of heat, energy, & matter in systems
List and explain 3 types of systems.
1)Isolated - cannot exchange matter or energy with its
surroundings
2) Closed - may exchange energy, but not matter, with the surroundings
3) Open - may exchange matter, energy, or both with the surroundings
What kind of system would you classify the human body as? Justify your choice
The human body is an open system
• exchange of matter (air, food in & waste out)
• exchange of heat (e.g. via homeostasis)
What is the 1st law of thermodynamics? (3)
the total energy of a system (including surroundings) remains constant
• energy cannot be gained or lost
• it can be transferred from part to part
• It can be converted from one form to another
What is the 2nd law of thermodynamics?
total entropy of a system must increase for a process to occur spontaneously.
What determines how energy flows and whether reactions occur?
Gibbs free energy (G)
What is Gibbs free energy?
• energy available to reactants/products in rxn
• determines the feasibility of reactions i.e. direction &
extent
Two forms of G used in chemical reactions
ΔG, the change in G of rxn
ΔG°, the standard ΔG (reactants/products @ 1mol/L)
ΔG° useful only under standard conditions
ΔG is determined by two factors. what are them?
Enthalpy (ΔH) – change in heat of reactants and
products of a rxn (e.g. chemical bonds)
• Entropy (ΔS) – change in randomness/disorder of
reactants & products
ΔG can also be defined for ideal gas reactions. what is the formula?
ΔG = ΔG° + RT ln [B]/[A] At constant P (pressure) & T (absolute) – thermal equilibrium R = gas constant (8.315 J/mol/K) In = natural logarithm [B] = concentration of product [A] = concentration of reactant
What happens to Gibbs free energy under standard conditions?
ΔG = ΔG°
ΔG° is predictive only under standard conditions
ΔG & ΔG° can differ greatly depending on [A], [B]
What is the formula for standard gibbs free energy at equilibrium?
At equilibrium ΔG = 0
0 = ΔG° + RT lnKeq
ΔG° = – RT lnKeq
how does a reaction become feasible?
As long as the sum of ΔG is –ve the pathway is
feasible.
