Lecture 1: Bioenergetics Flashcards
Benjamin Murray (life- long alcoholic) developed symptoms of:
dermatitis, diarrhea, dementia
Deficiency in the B-Vitamin niacin, present at low levels in alcoholics presents the classical symptoms of _____
pellagra
ethanol inhibits intestinal absorption of niacin
Deficiency in niacin affects many ________enzymes
dehydrogenase
The Free Energy Change (ΔG) for a reaction is:
ΔGreaction = Gproducts – Greactants
When ΔG is negative (<0), reaction occurs _________ it is ______ and the reaction proceeds to the _____
spontaneously, exergonic, right
When ΔG is positive, the reaction requires _____ to proceed; it is ______ and the reaction does not occur _______
energy, endergonic, spontaneously
At equilibrium ΔG =
0
in ΔG is related to the _______ of a reaction
directionality
Standard free energy change =
ΔG0’
Change in ΔG is related to the directionality of a reaction but not___
to its rate or path it follows.
G = ΔG0’ under which conditions?
25°C
1 atm pressure
1M Initial concentration of reactants and products
Except [H+], which is 1 x 10-7 M (so pH is 7.0)
The Laws of Thermodynamics
1st: Energy can be neither created nor destroyed. The total energy of the universe is constant
2nd: Systems tend toward disorder. Entropy increase in the universe
Entropy Equation
ΔG = ΔH - TΔS
Where:
ΔH is the change in enthalpy or heat content of system
ΔH = Hproducts - Hreactants
T is absolute temperature in Kelvin
ΔS is the change in entropy
For ΔG to be neg:
Either ΔH is neg.
Or TΔS is pos
Or both
The chemical energy of a compound is affected by:
Bond strain
Resonance forms
Steric effects
Solvation
When products have less chemical energy (are more stable) than reactants, the excess ____ is liberated as ____ and ΔH is ____.
energy, heat, negative
Relationship between ΔG0’ and the Equilibrium Constant, Keq
ΔG0’ =
-RT x 2.303 log Keq
R is ideal gas constant (1.987 x 10-3 kcal/mol-K)
T is temperature in Kelvin
Typically, if ΔG0’ is between +3 and -3 kcal/mol, reactions are driven by
“mass action” effects
CP levels kept around ____ in muscle; used as phosphoryl donor to rapidly synthesize ATP when [ATP] low in muscle
30 mM
During sudden exercise, _________, and CP transfers a phosphoryl group to ADP
ATP is depleted
______ is a high energy compound
ATP
Has two phosphoanhydride bonds that, when hydrolyzed, yield a lot of free energy. It has a large negative ΔG0’ (hydrolysis)
5 examples of high energy compounds are:
Phosphate anhydrides (ATP), enol phosphates (PEP), acyl phosphates (1,3-BPG), guanidinium phosphates (CP) and thiol esters (acyl-CoAs)
The transphosphorylation of ATP to ADP requires what cofactor?
Mg2+
Reasons for large negative Delta G0’ of hydrolysis of ATP
- Resonance stabilization of the product inorganic phosphate
- Less electrostatic repulsion (bond strain) in product (ADP) compared to reactant (ATP)
- Greater degree of solvation (hydration) of products compared to reactants
