Chapter 14 Flashcards
Define “metabolism”
A broad term that refers to the entire network of chemical reactions carried out by living cells.
Define “metabolite”
Small molecule intermediates produced during the degradation and synthesis of biopolymers
What distinguishes a catabolic reaction from an anabolic reaction?
Catabolic reactions degrade larger polymers to create smaller molecules and release energy, which is often stored in the form of high energy compounds (like ATP) or in the form of reduced cofactors (like NADPH).
Anabolic reactions deal with the synthesis of polymers
What does the symbol ΔGo’ symbolize?
Biological standard state
How would one calculate the actual ΔG for the sample reaction A + B –> C + D?
ΔGrxn=ΔGo’ + RTln ([C][D]/[A][B])
Knowing the actual ΔG for a reaction allows you to determine ________.
The overall directionality of a metabolic reaction.
When a reaction reaches equilibrium, what does ΔG equal?
0
Mathematically express how to calculate ΔGo’ using Keq. Express why the substitution of Keq can be made.
ΔGo’= -RTlnKeq, because the definition of Keq is the concentration of products over reactants at equilibrium
There are 3 implications of thermodynamics for metabolic pathways. List them.
- Metabolic pathways are irreversible
- Every metabolic pathway has a committed step
- Catabolic and anabolic reactions differ, and cannot completely run in reverse
What causes a metabolic pathway to be irreversible?
At least one reaction in the pathway having a ΔG«0. Gives each pathway overall directionality
What is a committed step? Reference pathway regulation.
An irreversible (exergonic) reaction that prevents the substrate from reacting in reverse and sends it forward down the pathway. Most regulation of a pathway is focused on altering the activity of the enzyme that carries out that committed step.
Carbon compounds consumed by catabolism are destined to eventually be converted to ____, the most oxidized compound, during the citric acid cycle
CO2
(T/F) The differences in reduction potentials can provide energy to drive many biological reactions, but not the synthesis of ATP.
False. Enough energy can be provided to synthesize ATP.
The reduction potential of a reducing agent is a measure of its ______ _______.
Thermodynamic reactivity.
Using the half reaction 2H+ + 2e- —> H2 as a reference, what would a negative value of E tell you about another reaction? Positive?
A negative E value would indicate that the substrate has a lower affinity for electrons than H+. A positive E value would indicate that the substrate has a higher affinity for electrons than H+.
