The TCA Cycle and Oxidative Phosphorylation
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What 3 things go into the Kreb’s cycle?
• glucose (by glycolysis) • fatty acids (beta oxidation) • amino acids (transamination)
Where does the Kreb’s cycle?
Mitochondrial matrix
What tissues does this occur in?
All tissues with mitochondria
Give details on the Link’s reaction
Pyruvate is converted to Acetyl CoA Pyruvate dehydrogenase is needed for this to work This reaction releases carbon dioxide and NADH Happens twice as glycolysis produces 2 pyruvate molecules
What is the chemical structure of oxaloacetate?
OOC-C=O-CH2-COO
What are the 1st 4 reactions of the Krebs cycle?
1) Condensation reaction - oxaloacetate is converted to citrate 2) Isomerisation (citrate to isocitrate) 3) First loss of carbon dioxide (6 carbon molecule forms a 5 carbon molecule). Isocitrate forms glutarate 4) Second loss of carbon dioxide. Oxoglutarate to succinyl CoA
What are the 2nd 4 reactions of the Krebs cycle?
5) Trapping thioester bond energy at GTP (GTP molecule is released here) 6) Conversion of succinate to fumarate (formation of FADH2) 7) Conversion of fumerate to malate 8) Conversion of malate to oxaloacetate
What allows the regeneration of glucose from pyruvate?
pyruvate carboxylase
What is essential that succinyl CoA makes? How about glutamate?
Haem Other amino acids, purines
What do you need to add to pyruvate to make oxoloacetate?
COO
What are 3 examples of oxidation reactions?
• Add oxygen directly to a molecule • Remove one electron • Remove a pair of hydrogen atoms
What are some key points on oxidative phosphorylation?
Location - mitochondria (cristae) Tissues - most tissues except red blood cells Function - direct phosphorylation of ADP to produce ATP
What are the 2 components of the electron transport chain?
• H pair acceptors (flavin cofactors, coenzyme) 2. Electron acceptors (iron sulphur protein, cytochrome proteins
What molecules help transport down the electron chains?
Iron-sulphur proteins - the iron can gain/lose electrons and hence transport them HAEM ring of cytochrome protein (electron acceptors).
What are redox carriers?
• every cofactor involved in oxidation/reduction reaction can be assigned a value known as the oxido-reduction potential • this redox potential describes the ability of the carrier to donate its electrons to another electron acceptor molecule • electrons flow from a carrier with a negative E0 to a carrier with a more positive value
Explain the movement of electrons in the electron transport chain
The electrons pass down the chain and go down in energy. The energy changes the conformation in the protein which allows them to move the protons from the mitochondrial matrix to the inter-membrane space.
What are the two gradients which are created by the movement of protons across the inner membrane?
• pH gradient - voltage potential
What is the change in energy across the membrane to get ADP and Pi to bond?
Kinetic to mechanical
What complexes move hydrogen ions out the cell?
1, 3 and 4
Give some inhibitors and uncouplers of oxidative phosphorylation
Inhibitors = CN- , CO and rotenone Uncouplers = DNP, thermogenin protein in brown adipose tissue
What does the brown adipose tissue harness the energy from the electron transport chain for?
for heat, not to make ATP
When metabolism takes place in aerobic tissue, oxygen utilisation results mainly from:
its reduction to water by cytochrome oxidase
How many reactions in the TCA cycle produce NADH and H+ from NAD-?
3
The electron transport chain is made up of a chain of electron carriers with: —– electron affinity and —– redox potential
increasing, increasing