BIOCH200 Lecture Notes - Lecture 14: Phosphocreatine, Anabolism, Endergonic Reaction
5 May 2018
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Biochemical Standard State
❏pH = 7
❏Substrate and Product concentration is 1M
❏Temperature is 25
❏Pressure 1 atm.
❏Water is not considered in the equation.
❏Signs of G tell us if
❏Negative = forward direction
❏Positive = backwards direction.
❏Delta G close to zero → near equilibrium
❏Therefore Delta G tells us direction and Magnitude.
❏Reaction with positive biochemical standard state may have a negative actual free
energy under cellular conditions
Example
A ←---> B
❏Equilibrium is 1:4 and Standard Conditions are 1:1. Which way does the reaction proceed?
❏We need to get standard condition to equilibrium → Forward direction.
Metabolic Pathways
❏First and Last step regulated through allostery or phosphorylation.
❏Synchronous regulation or irreversible reactions.
❏Synchronous → turn on A and e together, and turn them off together.
❏Intermediates can typically maintain equilibrium concentration.
High Energy Intermediates
❏Contain usable chemical energy that can be recovered or used by the cell
❏Three Types
1. Electron Carriers (NADH,NADPH, FADH2, FMNH2)
a. NAD NADP, FAD, FMN are electron acceptors not considered high energy
2. Nucleotide Triphosphates (NTPS; ATP, GTP, UTP) and diphosphates (because of
anhydride bonds)
3. Thioesters.
Oxidation/Reduction Reactions
❏Carbolism → Oxidative where metabolites are oxidized (lose electrons) and cofactors are
reduced (oxidizing agents) → NAD+, FAD, NADP+
❏Anabolism → Reductive where metabolites are reduced (gain electrons) and cofactors are
oxidized (reducing agents) → NADPH
Oxidized States of Carbon from Least oxidized to most oxidized
Reduction of Cofactors
❏NAD+ and NADP+ go from C-OH to C=O
❏FAD goes from C-C bond to C=C bond.
ATP
❏Generated by metabolism directly and through reoxidation of NADH/FADH2 by ETC
❏Used in driving unfavourable reaction s(coupling) and movement and active transport (ion
pumping)
Thioesters
❏High energy
❏Similar to esters but no electron delocalization
❏OH + Carboxylic acid → Esters (resonance)
Document Summary
Water is not considered in the equation. Delta g close to zero near equilibrium. Therefore delta g tells us direction and magnitude. Reaction with positive biochemical standard state may have a negative actual free energy under cellular conditions. Equilibrium is 1:4 and standard conditions are 1:1. We need to get standard condition to equilibrium forward direction. First and last step regulated through allostery or phosphorylation. Synchronous turn on a and e together, and turn them off together. Contain usable chemical energy that can be recovered or used by the cell. Three types: electron carriers (nadh,nadph, fadh2, fmnh2, nad nadp, fad, fmn are electron acceptors not considered high energy, nucleotide triphosphates (ntps; atp, gtp, utp) and diphosphates (because of anhydride bonds, thioesters. Carbolism oxidative where metabolites are oxidized (lose electrons) and cofactors are reduced (oxidizing agents) nad+, fad, nadp+ Anabolism reductive where metabolites are reduced (gain electrons) and cofactors are oxidized (reducing agents) nadph.
