Bioenergetics Flashcards
Catabolism is
going from energy containing nutrients (carbs, fats, proteins) to energy depleted end products (CO2, H20, NH3) in order to make ATP, NADH, NADPH, FADH2
Anabolism is
Using ATP, NADH, NADPH, FADH2 to take precursor molecules (Amino acids, sugars, fatty acids, and nitrogenous bases) and turn them into cell macromolecules (proteins, polysaccharides, lipids, and nucleic acids).
what is the energy mechanism for the movement of muscles?
Using ATPase to harness the energy of ATP to move the myosin head (which is anchored to the myosin thick filament) further along the thin filament.
Describe how the cell maintains homeostasis
The sodium pump: three Na out and take in 2 K ions. Creates a concentration gradient and an electrochemical gradient. Inside of cells is electronegative versus the outside (inside K+ is 140 mM, Na+ 12mM. outside the cell K+ 4mM and Na+ is 145mM). The outside of the cell is at 50-70 mV potential. This is particularly important for neurons. The pump uses ATP >phosphate is transferred to covalently modify an aspartate residue on the sodium pump protein.
List the different forms of kinetic energy in living systems
A. Radiant energy: carried in photons from sun, the ultimate source of all forms of energy in living systems.
B. Thermal energy: Protein molecules function optimally at a particular temperature or need certain thermal energy to function.
C. Mechanical energy: movement of cells and cell components.
D. Electric energy: movement of charged particles down gradients of electric potential.
List the different forms of potential energy in living systems
A. Stored in chemical bonds.
B. Stored in concentration gradients.
C. Stored in electric fields from charge separation.
D. Stored in redox pairs.
What is the first law of thermodynamics
Energy is neither created, nor destroyed. Energy can be converted into different forms but is always conserved
What is the second law of thermodynamics
The entropy (S) is always increasing: the disorder is always increasing (heat is always being dispersed rather than collected into one spot)
Combustion of glucose demonstrates…
an increase in entropy (delta S is positive). You go from one glucose molecule and 6O2 to 6H2O and 6CO2. There is an increase in the number of molecules and also a bigger distribution between the liquid molecules and the gas molecules
The thermodynamic driving force for a rxn is
The change in Gibb’s free energy (- is favorable, + is not favorable).
DG = Gproducts - Greactants
DG = DH - TDS
The maximal amount of useful work that can be done by a system is defined by delta G.
Negative DG indicates:
Positive DG indicates:
A reaction is thermodynamically favorable and will occur spontaneously at constant temp.
When it is positive, this indicates that the reaction is thermodynamically unfavorable and will not occur spontaneously at constant temp.
What is enthalpy and how does it change depending on whether the reaction is endothermic or exothermic?
the change of bond energy of a reaction (DH) is the Hproducts-Hreactants.
Exo: heat is released and DH is negative (favorable)
Endo: heat is absorbed and DH is positive (unfavorable)
What is entropy and how does it change depending on whether the reaction is favorable or unfavorable?
DS is Sproducts-Sreactants and it is the change in randomness of a reaction. Favorable= DS positive. Unfavorable=DS is negative
Name a major way that the cell harnesses energy for the production of ATP
Oxidation of glucose DG is -686 kcal/mol. (however, the actual amount that we can harness is 30% and the rest is lost to heat).
What limits the rate of a reaction?
The activation energy (this is why a donut on the table is kinetically stable and not spontaneously combusting). Therefore, a reaction that is favorable may not happen if there is a high activation energy. This is why you need ENZYMES to digest and to decrease (or supply) the amount of activation energy needed.
What are the equations for Gibbs free energy in 1. a chemical reaction and for 2. a redox reaction?
- For a chemical reaction:
DG = DH - TDS
H=enthalpy, S=entropy, T= ºK - For a redox reaction:
DG = -nFDE
n= #electrons transferred, F = Faraday constant,
DE= difference in reduction potential in volts
Apply the following basic thermodynamic equations that describe the relationship between free energy, the equilibrium constant, enthalpy and entropy and calculate one unknown variable in an equation when all other variables are given.
ΔG =ΔG0 + RT ln [PRODUCTS]/[REACTANTS]
ΔG0 = - RT lnKeq ΔG = ΔH - T ΔS
Describe the relationship between the sign of the standard free energy and the direction of a reaction under standard conditions.
If ΔG’0 is less than 0 Keq is greater than 1.0 and the reaction proceeds forward
If ΔG’0 is equal to 0 Keq is equal to 1.0 and the reaction is at equilibrium If ΔG’0 is greater than 0 Keq is less than 1.0 and the reaction proceeds in reverse
Describe the effect of positive/negative entropy or enthalpy on the thermodynamic forces driving a reaction based on the equation: ΔG = ΔH – T ΔS.
If ΔG is positive the reaction is nonspontaneous and requires energy input to proceed (condition supported by positive enthalpy and negative entropy)
If ΔG is negative the reaction is spontaneous (condition supported by positive entropy and negative enthalpy)
Calculate the numerical conversion between free energy (ΔG) and Redox potential (ΔE) in biological systems.
ΔG = -nFΔE
n- number of electrons transferred
F- faraday’s constant
Two classes of “high energy” bonds:
Thioester bonds C-S: acetyl CoA Hi energy phosphate bonds: Phosphoanhydride (P-O-P) bonds: (ATP) P-N bonds: phosphocreatine C-O-P bonds: phosphoenolpyruvate
