BIOC312 Lecture Notes - Lecture 6: Thioester, Malate Dehydrogenase, Symporter

11 views10 pages
22 Jul 2016
Department
Course
Professor
Lecture 6; Citric Acid Cycle
Aerobic catabolism (Oxidation reactions)
Intermediates used for biosynthetic reactions
Takes place in the mitochondria in eukaryotes or the cytosol in bacteria
Energy of the osidation reactions is largely conserved as reducing
power stored in coenzymes. Main coenzymes;
o NAD+ NAHD
o Ubiquitone (Q) Ubiquinol (QH2)
lOMoARcPSD
Pyruvate translocase transports pyruvate into the mitochondria in symport
with H+, where it is coupled to an enzyme A and is decarboxylated and
oxidized by huge enzyme complex pyruvate dehydrogenase. This process
uses a little energy and concentration gradient of protons is required provided
by the citric acid cycle.
For each acetyl CoA that enters; 2 molecules CO2 released, Coenzymes
NAD+ and Q are reduced, 1 GDP (or ADP) is phosphporylated and initial
acceptor (Oxaloacetate) is regenerated.
Steps;
1. Oxidative decarboxylation of pyruvate to Acetyl CoA (In the pyruvate
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 10 pages and 3 million more documents.

Already have an account? Log in
dehydrogenase complex). NADH is formed.
2. Addition of acetate group derived from Acetly CoA to end product of citric
acid cycle (Oxaloacetate), yielding citrate (6C tricarboxylic acid). Hydrolysis
of the high energy thioester bond in acetyl CoA drives this reaction, catalysed
by citrate synthase.
3. Isomerisation of citrate to give isocitrate catalysed by aconitase
lOMoARcPSD
4. Another strongly exothermic oxidative decarboxylation reaction carried
out by the enzyme isocitrate dehydrogenase., yielding 5C compound
ketoglutarate and the energy is conserved in the reducing enzyme NADH
5. Antoher strongly exothermic oxidative decarboxylation reaction carried
out by the enzyme complex ketogluterate dehydrogenase, yielding succinyl α
CoA and the energy is conserved in both the thioester linkage of HS-CoA as
well as the reduced coenzyme NADH
6. Hydrolysis of thioester bond and removal of coenzyme A, yielding 4C acid
succinate, This energy is conserved by direct phosphorylation of GTP (Or
ATP) by enzyme (Succinyl CoA synthetase)
7. Oxidation of succinate to fumarate (Generates double C=C bond) .
Reducing power (energy) is conserved by the formation of the reduced
coenzyme ubiquinol (GH2) in membrane- bound complex called succinate
dehydrogenase or Complex II
8. Hydration of the double bond in fumurate yields malate catalysed by
fumurate dehydratase, simply a rearrangement preparing for final reaction.
9. Oxidation of malate to oxaloacetate, ‘last’ intermediate in the cycle.
Malate dehydrogenase conserves energy by coupling oxidation to the
reduction of coenzyme NADH.
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 10 pages and 3 million more documents.

Already have an account? Log in
lOMoARcPSD
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 10 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class