Chapter 13: Metabolism
what conditions allow for a spontaneous (negative GFE) reaction?
a negative H and a positive S H is the enthalpy or heat content, roughly the number of kinds of bonds S is the entropy or measure of disorder in the reaction
what are the three components of a nucleotide?
a sugar molecule, a phosphate group and a nitrogenous base (ATCGU)
ATP can transfer energy via a. direct hydrolysis of an ATP molecule with water displacing a phosphate group b. a phosphoryl, pyrophosphoryl, or adenylyl group is transferred to the substrate or enzyme, then displaced as a leaving group c. the entire ATP molecule bonds directly to the substrate or enzyme for the duration of the reaction d. ATP does not supply energy for metabolic reactions
a. direct hydrolysis of an ATP molecule with water displacing a phosphate group
how do you predict the ∆G⁰' for a reaction?
as entropy increases ∆G⁰' decreases so more product than reactant is going to result in a negative ∆G⁰' while the opposite will result in a positive, and an equal amount results in a ∆G⁰' of zero
both reactions, A ->B and C->B are endergonic, however, A -> C is a favorable reaction, which of the following must be true of A->C? (select all that apply) a. the coupled reaction is A -> B + C -> B b. the coupled reaction is A->B->C c. the absolute value of ∆G of A->B is smaller than the absolute value of ∆G of B->C d. the absolute value of ∆G of A->B must be greater than that of C->B
b. the coupled reaction is A->B->C c. the absolute value of ∆G of A->B is smaller than the absolute value of ∆G of B->C for a reaction to be favorable, the overall change in Gibbs free energy (∆G) must be negative so, if A → B has a smaller absolute value of ∆G than B → C, it means A → B is more favorable, and the overall reaction A → C could be favorable
NAD(P)H is _________ a. nearly always a part of a catabolic reaction b. the usual coenzyme in reductions c. generally present at a lower concentration than NADP+ d. a pyridine nucleotide without an added hydride ion
b. the usual coenzyme in reductions
in order for a metabolic pathway to proceed in the cell a. ∆G°' has to be zero or negative for all reactions b. ∆G has to be zero or negative for all reactions c. ∆G°' and ∆G have to be zero or negative for all reactions d. ∆G‡ has to be zero or negative for all reactions
b. ∆G has to be zero or negative for all reactions metabolic pathways involve a lot of consecutive reactions taking place so each one needs to be spontaneous to keep things moving and a negative delta G corresponds to a spontaneous reaction
which of the following statements is true? a. auto- and chemotrophs use both light and organic compounds to make energy b. hetero- and autotrophs use both light and organic compounds to make energy c. chemoheterotrophs use organic compounds to make energy d. autotrophs can exist purely on light alone
c. chemoheterotrophs use organic compounds to make energy autotrophs can produce their own energy from inorganic sources like light or chemicals heterotrophs rely on organic compounds produced by other organisms for their energy chemoheterotrophs obtain energy by breaking down organic compounds through chemical processes
The formation of a protein's secondary structure increases order within the peptide, however, according to the second law of thermodynamics, the process is still spontaneous because: a. more stable bonds are formed than broken b. increased order does not affect ΔG c. entropy of the surroundings increase d. it is not actually spontaneous
c. entropy of the surroundings increase
steady state is best described as a state of a. equilibrium b. dynamic flux c. homeostasis d. constant energy
c. homeostasis
what is NOT a way that ATP can be used to supply energy? a. supplying energy for active transport across a membrane b. supplying energy to myosin and actin to turn chemical energy into motion c. supplying energy through hydrolysis to produce conformational changes d. Supplying energy by being a storage molecule of energy
d. Supplying energy by being a storage molecule of energy ATP is not a storage molecule it is an energy carrier
what is the second law of thermodynamics?
disorder (entropy) in the universe increases, a process is only spontaneous when entropy of the universe increases
the 2nd law of thermodynamics explains why: a. the formation of chemical bonds can produce heat b. an enzyme operates more slowly at suboptimal temperatures c. protein folding is a spontaneous process d. A and C e. B and C
e. B and C
what would the energy diagrams for a reaction with delta G = 0, delta G < 0, and delta G > 0 look like?
free energy along the y-axis and the reaction coordinate along the x-axis, G < 0 has a lower product curve than the reactants and the G > 0 is the opposite, G = 0 has them land at equal points
if Keq < 1, the ∆G'° is _______ if Keq > 1, the ∆G'° is________ if Keq = 1, the ∆G'° is ________
if Keq < 1, the ∆G'° is positive if Keq > 1, the ∆G'° is negative if Keq = 1, the ∆G'° is zero
how can you determine the change in entropy of a given reaction?
if the number of moles from the products to the reactants decreases then so does the entropy of the system
what are two ways that allow unfavorable reactions to be carried out within the cell?
reaction coupling a favorable reaction to an unfavorable one and the use of enzymes
catabolism _______ energy, while anabolism _______ energy
releases, absorbs
why is knowing Q critical for determining whether a reaction is spontaneous or nonspontaneous?
sometimes the actual concentrations of products and reactants are far from standard conditions, ΔG = ΔG'0 + RTlnQ, and a reaction that is unfavorable at standard conditions may be favorable at physiological conditions
what is the first law of thermodynamics?
the total amount of energy in the universe is constant, therefore energy cannot be created or destroyed
how many high phosphoanhydride energy bonds does ATP have?
two
plants make glucose from ______ and _______
water and carbon dioxide
