Download Citrate cycle - 3.LF UK 2015

Citrate Cycle (CC)
- exercise -
Vladimíra Kvasnicová
Citrate cycle is also called
a) citric acid cycle
b) tricarboxylic acid cycle
c) Krebs cycle
d) electron transport chain
Citrate cycle is also called
a) citric acid cycle
b) tricarboxylic acid cycle
c) Krebs cycle
d) electron transport chain
The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations,
4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
simplification:
The figure is found at http://www.sp.uconn.edu/~bi107vc/images/mol/krebs_cycle.gif (December 2006)
citric acid
(2-hydroxypropane-1,2,3-tricarboxylic acid)
Hans Adolf Krebs
The Nobel Prize in Physiology or Medicine in 1953
for his discovery of the citric acid cycle.
= the other metabolic pathway
The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical
Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Citrate cycle
a) is a catabolic pathway
b) participates in anabolic reactions
c) belongs among oxidative processes
d) produces carbon dioxide
Citrate cycle
a) is a catabolic pathway
b) participates in anabolic reactions
c) belongs among oxidative processes
d) produces carbon dioxide
The figure is found at http://www.holon.se/folke/kurs/Distans/Ekofys/Recirk/Eng/regcyc5.jpg (December 2006)
Amphibolic nature
of the
citrate cycle
The figure is found at
http://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html
Enzymes of the citrate cycle
a) are found in all cells
b) are located in a mitochondrion
c) catalyze freely reverzible reactions
d) produce coenzymes which are regenerated
in a respiratory chain
Enzymes of the citrate cycle
a) are found in all cells
b) are located in a mitochondrion
c) catalyze freely reverzible reactions
d) produce coenzymes which are regenerated
in a respiratory chain
strongly exergonic
reactions
The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)
The substances enter the CC
a) acetyl~CoA
b) NAD+ and FAD
c) carbon skeleton of amino acids
d) GDP
The substances enter the CC
a) acetyl~CoA (→ 2 CO2)
b) NAD+ and FAD (→ NADH+H+ + FADH2)
c) carbon skeleton of amino acids
d) GDP (→ GTP)
The figure is found at http://www.elmhurst.edu/~chm/vchembook/images/590metabolism.gif (December 2006)
Choose products of the cycle
a) pyruvate
b) acetyl-CoA
c) NADH
d) FADH2
Choose products of the cycle
a) pyruvate
b) acetyl-CoA
c) NADH (→ electron transport chain)
d) FADH2 (→ electron transport chain)
Products of the citrate cycle
The figure is found at http://www.hupe.hu/szerv/tanszekek/kio/im/oktat/SEJTBIO/citratkor/citr_summa_e.html
(December 2006)
Energy released from oxidation of
acetyl group in the CC is conserved in
a) GTP
b) ATP
c) NADH
d) FADH2
Energy released from oxidation of
acetyl group in the CC is conserved in
a) GTP (succinyl~Co → succinate)
b) ATP (GTP + ADP → GDP + ATP)
c) NADH (3x)
d) FADH2 (1x)
The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)
NAD+ is reduced to NADH+H+ in the
reactions of the CC
a) isocitrate → -ketoglutarate
b) -ketoglutarate → succinyl~CoA
c) succinate → fumarate
d) malate → oxaloacetate
NAD+ is reduced to NADH+H+ in the
reactions of the CC
a) isocitrate → -ketoglutarate
b) -ketoglutarate → succinyl~CoA
c) succinate → fumarate
d) malate → oxaloacetate
„F“ → Fumarate and
FADH2
The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)
Carbon dioxide (CO2) is produced in the
reactions of the CC
a) oxaloacetate + acetyl~CoA → citrate
b) citrate → isocitrate
c) isocitrate → -ketoglutarate
d) -ketoglutarate → succinyl~CoA
Carbon dioxide (CO2) is produced in the
reactions of the CC
a) oxaloacetate(C4) + acetyl~CoA(C2) →
citrate(C6)
b) citrate (C6)→ isocitrate (C6)
c) isocitrate (C6) → -ketoglutarate (C5)
d) -ketoglutarate (C5) → succinyl~CoA (C4)
! count number of carbons !
The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)
Choose reactions that lead to
net synthesis of CC intermediates
(= anaplerotic reactions)
a) pyruvate → acetyl~CoA
(PDH)
b) pyruvate → oxaloacetate
(pyruvate carboxylase)
c) aspartate → oxaloacetate
(AST)
d) glutamate → -ketoglutarate
(ALT)
Choose reactions that lead to
net synthesis of CC intermediates
(= anaplerotic reactions)
a) pyruvate → acetyl~CoA
(PDH)
b) pyruvate → oxaloacetate
(pyruvate carboxylase)
c) aspartate → oxaloacetate
(AST) – the reaction
consumes 2-oxoglutarate (+1 -1 = 0 net synthesis)
d) glutamate → -ketoglutarate
(ALT)
The figure is found at http://web.indstate.edu/thcme/mwking/tca-cycle.html (prosinec 2006)
The most important anaplerotic reaction:
pyruvate carboxylase
The figure is found at http://www.bmb.leeds.ac.uk/illingworth/metabol/2120lec3.htm#krebs (December 2006)
The substances can be synthesized from
intermediates of the CC
a) amino acids
b) heme
c) glucose
d) fatty acids
The substances can be synthesized from
intermediates of the CC
a) amino acids
b) heme
c) glucose
d) fatty acids
Citrate cycle
as a source of
substrates used
in a synthesis of
other molecules
The figure is found at
http://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html
The enzymes regulate velocity of the CC
a) citrate synthase
b) isocitrate dehydrogenase
c) -ketoglutarate dehydrogenase
d) hexokinase
The enzymes regulate velocity of the CC
a) citrate synthase
b) isocitrate dehydrogenase
c) -ketoglutarate dehydrogenase
d) hexokinase
The citrate cycle is inhibited by
a)  ATP/ADP
b)  NADH,  NAD+
c)  NADH/NAD+
d)  AMP
The citrate cycle is inhibited by
a)  ATP/ADP
b)  NADH,  NAD+
c)  NADH/NAD+
d)  AMP
Regulation of the citrate cycle
= by availability of substrates and consumption of produts
regulatory
enzyme
citrate synthase
activation
isocitrate
dehydrogenase
(key enzyme)
  ATP / ADP
2-oxoglutarate
dehydrogenase
 Ca2+
inhibition
  NADH / NAD+
 succinyl-CoA
  NADH / NAD+
  ATP / ADP
  NADH / NAD+
  ATP / ADP
 GTP
 succinyl-CoA
Citrate
a) is formed from oxaloacetate and acetic acid
b) is transported to the cytoplasm if accumulates
c) acts as an inhibitor of glycolysis
d) activates synthesis of fatty acids
Citrate
a) is formed from oxaloacetate and acetic acid
b) is transported to the cytoplasm if accumulates
c) acts as an inhibitor of glycolysis
d) activates synthesis of fatty acids
energy excess → it is stored in a glycogen and fat
ATP
The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)
see next
presentation
The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical
Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2