CH 3 Flashcards
Your body extracts energy from the food you ingest by catalyzing reactions that essentially “burn” the food molecules in a stepwise fashion. What is another way to describe this process?
oxidation
Oxidation is a favorable process in an aerobic environment, which is the reason cells can derive energy from the oxidation of macromolecules. Once carbon has been oxidized to __________, its most stable form, it can only cycle back into the organic portion of the carbon cycle through __________.
CO2, photosynthesis
For the reaction Y → X at standard conditions with [Y] = 1 M and [X] = 1 M, ΔG is initially a large negative number. As the reaction proceeds, [Y] decreases and [X] increases until the system reaches equilibrium. How do the values of ΔG and ΔG° change as the reaction equilibrates?
ΔG becomes less negative and ΔG° stays the same.
The equilibrium constant (K) for the reaction Y → X can be expressed with respect to the concentrations of the reactant and product molecules. Which of the expressions below shows the correct relationship between K, [Y], and [X]?
K = [X]/[Y]
If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B?
K = [AB]/[A][B]
NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional __________ and one additional __________. This combination can also be referred to as a hydride ion.
electrons, proton
T / F
Activated carriers provide energy for unfavorable reactions and are “reloaded” when coupled to favorable reactions.
True
Chemical reactions are reversible; they can proceed in both the forward and reverse directions. If the ΔG° for the reaction Y → X is energetically favorable, how can you explain the fact that not all the Y molecules will be converted to X molecules?
As Y -> X, the [Y] decreases and [X] increases, which makes ΔG less negative and the reaction less favorable as the reaction nears equilibrium.
Heat:
form of energy arising from random motion of molecules
Entropy:
measure of disorder
Enzyme use in redox reactions
catalysts that transfer electrons to make/break bonds
Addition of hydrogens is…
reduction
Removal of hydrogens is…
oxidation
equilibrium constant is directly proportional to…
delta G°
delta G =
(c+d) - (a+b)
enzymes can speed up rate but cannot change the
delta G°
why do we need energy
to perform unfavorable reactions through coupling
Delta G equation
G = G° + RT ln [Prod]/[React]
delta G° is________ of concentration
independent ~ only intrinsic properties of products + reactants
The Equilibrium Constant (K) Is Directly Proportional to delta G°
-5.94 log K
Sequential reactions
X -> Y unfavorable (+delta G)
Y -> Z very favorable (-delta G)
Y -> Z reaction siphons the X-Y reaction
In general, enzymes and substrates are found in relatively _____ concentrations to water
low
the larger K, the greater distance between associated and dissociated states, leading to a ____ binding site interaction between the two molecules
stronger
siphoning reaction
Siphoning, where a favorable reaction lowers the concentration of the product of an
unfavorable reaction, driving the reaction to occur
Nad+
NADPH
NAD+ - oxidizing agent in catabolic reactions that generate ATP
NADPH - reducing agent in anabolic reactions
Condensation vs hydrolysis
Condensation - lost of H2O ~ unfavorable
Hydrolysis - gain of H2O ~ favorable
