Chapter 8 - Metabolic Pathways Flashcards
Hexokinase
first step in glycolysis, kinase is an enzyme that transfers terminal phosphate group of ATP unit to some other compound (-4.0 kcal/mol)
Phosphofructokinase
transferase, catalyzes conversion of fructose-6-phosphate to fructose-1,6-diphosphate (∆G°’ = -3.4 kcal/mol)
Aldolase
lyase, (∆G°’ = +5.7 kcal/mol)
How does DHAP convert to glyceraldehyde-3-phosphate?
isomers, rxn catalyzed by triose phosphate isomerase, once G3P is removed, DHAP is isomerized to G3P (∆G°’ = +1.8 kcal/mol)
When does the oxidation state of the C-1 carbon of glyceraldehyde-3-phosphate change?
Step 6, oxidation state of C-1 becomes +1, the enzyme glyceraldehyde-3-dehydrogenase will convert G3P into 1,3-DPG, which has an oxidation state of +3 on C-1, cofactors: NAD+ and Pi
Phosphoglycerate Kinase
won’t work unless ADP is present; produces 3-phosphoglycerate and ATP (remember we split the 6 carbon glucose molecule into two trioses) so there’s two 3-PG and 2 ATP
Phosphoglyceromutase
converts 3-PG to 2-PG; the enzyme is a phosphorylated enzyme so during an intermediate state, the phosphorous gets transferred to the C-2 position of 2-PG and phosphorous from 3-PG gets transferred to the enzyme (∆G°’ = +1.1 kcal/mol)
What is the importance of 2,3-BPG?
binds in the middle of hemoglobin and stabilizes the deoxy state so more oxygen is released to the tissue
Pyruvate Kinase
transfers phosphoryl group from PEP to ADP and gives pyruvate and ATP, this phosphorylation is nonoxidative (∆G°’ = -7.5 kcal/mol) remember that we have two 3-carbon pyruvates so we made 2 ATPs (net)
How is L-lactate synthesized from pyruvate?
In keto form, oxidation state is +2, so a 2 e- transfer would make a carbon with a zero oxidation state (L-lactate), the enzyme required is lactate dehydrogenase and we can reoxidize NAD for the debt from step 6
