Post on 21-May-2020
Respiratory chain (RCH)
� is found in all cells containing mitochondria
� is composed of 4 enzyme complexes
� the enzymes occur in the inner mitochondrial membrane
� RCH oxidizes NADH+H+ to NAD+ and FADH2 to FAD → electrons are transported to O2
� protons (H+) are transported to the intermembrane space ⇒ proton gradient
Recommended animations
• electron transport chainhttp://vcell.ndsu.nodak.edu/animations/etc/index.htm
• ATP synthesishttp://vcell.ndsu.nodak.edu/animations/atpgradient/index.htm
The figure is found at http://plaza.ufl.edu/tmullins/BCH3023/cell%20respiration.html (December 2006)
The figure is found at http://www.grossmont.net/cmilgrim/Bio220/Outline/ECB2Figures&Tables_Ed2-Ed1/Chapter14_13/REDOX_POTENTIALS_ElectronTransportChain_Fig14-21.htm (December 2006)
Gibbs energy„G“
Redox potential
„E“
↑ reducing properties
↑ oxidizing properties
The figure is found at http://academic.brooklyn.cuny.edu/biology/bio4fv/page/mito_ox.htm (December 2006)
The figure is found at http://www.cellml.org/examples/images/metabolic_models/the_electron_transport_chain.gif (December 2006)
Citrate cycle
succinate DH
The figure is found at http://web.indstate.edu/thcme/mwking/oxidative-phosphorylation.html (December 2006)
FADH2
Complex II can not transport H+
The figure is found at http://plaza.ufl.edu/tmullins/BCH3023/cell%20respiration.html (December 2006)
ATP synthase
inner mitochondrial membrane
The figure is found at http://departments.oxy.edu/biology/Franck/Bio222/Lectures/March23_lecture_shuttles.htm (December 2006)
Uncoupling proteins(UCP)
= separate RCH from ATP
synthesis(the synthesis is
interrupted)
energy from H+
gradient is released as a heat
Synthesis of ATP in cells is called
1. oxidative phosphorylation
alternative names
aerobic phosphorylation
2. substrate level phosphorylation(= formation of ATP without direct presence of oxygen;energy source for this ATP synthesis is an energy rich compound: 1,3-bisphosphoglycerate = 1,3-BPG, phosphoenolpyruvate = PEP, succinyl-CoA, GTP, creatine phosphate,...)
ATP (GTP) can be formed in these reactions
• 1,3-BPG + ADP → 3-phosphoglycerate + ATP (in glycolysis)
• PEP + ADP → pyruvate + ATP (in glycolysis)
• succinyl~CoA + GDP+Pi → succinate + GTP (in Krebs cycle)
• GTP + ADP → GDP + ATP
• creatine phosphate + ADP → creatine + ATP (in muscles)creatine kinase (CK)
• ADP + ADP → ATP + AMP(adenylate kinase = myokinase)
Adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Formation of reducing equivalents (NADH, FADH2)
• glycolysis (cytosol): 2 NADH
• pyruvate dehydrogenase (PDH): 1 NADH
• β-oxidation: (n/2)-1 FADH2 / (n/2)-1 NADH(n= number of carbons of FA)
• citrate cycle: 3 NADH, 1 FADH2
• glutamate dehydrogenase (GMD): 1 NADH
• interconversion of ketone bodies: 1 NADH
• oxidation of ethanol to acetic acid: 2 NADH(alcohol dehydrogenase/cytosol, aldehyde dehydrogenase/mitoch.)
MALATE-ASPARTATE SHUTTLE
Transport of reducing equivalents to mitochondria
The figure was accepted
from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc.,
New York, 1997. ISBN 0-471-15451-2
GLYCEROL PHOSPHATE SHUTTLE
The figure was accepted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Oxidative metabolism in mitochondria
• pyruvate dehydrogenase (PDH) glucose, amino acids
• glutamate dehydrogenase (GMD) amino acids
• β-oxidation of fatty acids fatty acids
• ketone bodies degradation ketone bodies
• Krebs cycle all nutrients
• respiratory chain – O2 NADH, FADH2
oxidative phosphorylation= ATP synthesis in cooperation with the respiratory chain
The figure is found at: http://faculty.uca.edu/~johnc/pdhrxns.gif (December 2006)
2-oxoacid dehydrogenase is a multienzyme complex
mitochondria
„pyruvatedehydrogenase reaction“ = PDH
= oxidative decarboxylation of pyruvate
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
The figure is found at http://www.sp.uconn.edu/~bi107vc/images/mol/krebs_cycle.gif (December 2006)
simplification:
The figure is found at http://www.holon.se/folke/kurs/Distans/Ekofys/Recirk/Eng/regcyc5.jpg (December 2006)
The figure is found athttp://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html
Amphibolic nature of the
citrate cycle
The figure is found at http://www.elmhurst.edu/~chm/vchembook/images/590metabolism.gif (December 2006)
The figure is found at http://www.hupe.hu/szerv/tanszekek/kio/im/oktat/SEJTBIO/citratkor/citr_summa_e.html(December 2006)
Products of the citrate cycle
The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)
„F“ → Fumarate andFADH2
The figure is found at http://web.indstate.edu/thcme/mwking/tca-cycle.html (prosinec 2006)
Anaplerotic reactions
The figure is found at http://www.bmb.leeds.ac.uk/illingworth/metabol/2120lec3.htm#krebs (December 2006)
pyruvate carboxylase
The most important anaplerotic reaction:
The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)
strongly exergonic reactions
Regulation of CC
Regulation of the citrate cycle
• ↑ NADH / NAD+
• ↑ ATP / ADP• GTP• succinyl-CoA
• Ca2+2-oxoglutarate dehydrogenase
• ↑ NADH / NAD+
• ↑ ATP / ADP• ↓ ATP / ADPisocitrate
dehydrogenase(key enzyme)
• ↑ NADH / NAD+
• succinyl-CoAcitrate synthase
inhibitionactivationregulatory enzyme
= by availability of substrates and consumption of produts
The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)
↑ATP
transported to the cytosol
Citrate
• is formed from oxaloacetate and activated acetic acid (acetyl-CoA)
• is transported to the cytoplasm if its concentration in a mitochondrion rises
• participates in inhibition of glycolysis
• activates fatty acid synthesis
excess of energy is stored in glycogen and fat
Recommended animations- SUMMARY -
1. Essential Biochemistry / Wiley & Sons(Exercises: 10, 11, 16, 17, 19, 20)http://www.wiley.com/college/pratt/0471393878/student/exercises/index.html
2. Interactive Concepts in Biochemistry / Boyerhttp://www.wiley.com/legacy/college/boyer/0470003790/animations/animations.htm
3. Fundamentals of Biochemistry / Voethttp://www.wiley.com/college/fob/anim/
4. Schematic Pathways / Hardyhttp://ull.chemistry.uakron.edu/Pathways/index.html
5. Virtual Cell Animation Collectionhttp://vcell.ndsu.nodak.edu/animations/home.htm