Citric Acid Cycle and OxPhos
What other "high-energy" compound is generated directly by the c.a.c?
GTP, equivalent to ATP.
How many ATP's are generated through ox/phos during the oxidation of FADH2?
FADH2 yields about 2 ATP/FADH2
What can be synthesized from α-ketoglutarate?
Glutamate, generated in one step by transamination.
What can be synthesized from succinyl CoA?
Heme synthesis.
Why is pyruvate dehydrogenase an important enzyme?
It is an enzyme that links glycolysis with the Citric Acid cycle. It converts pyruvate to acetyl CoA. Provides substrate for the c.a.c.
What is the role of the proton gradient in ox/phos?
It is the driving force for ATP production by the ATP synthase.
What are the citric acid cycle's catabolic functions?
It oxidizes the two carbon atoms of acetyl CoA to carbon dioxide (CO2), at the same time generating compounds such as reduced cofactors, NADH, and FADH2.
Why is pyruvate carboxylase an important enzyme?
It provides oxaloacetate to keep the citric acid cycle going if/when intermediates are removed for synthesis.
Why is the citric acid cycle (TCA) said to be amphibolic?
It serves both catabolic (degradative) and anabolic (synthetic) roles.
What are the two characteristic of an uncoupler of ox/phos?
1. Lipophilic: can pass through Inner mitochondrial membrane easily 2. Weak acids: can pick up a H+ easily
How many molecules of reduced cofactors are produced by the oxidation of one molecule of acetyl CoA by the TCA?
Acetyl CoA --> 3 NADH and 1 FADH2
From what metabolites is the citric acid cycle derived?
Acetyl CoA is from the breakdown of fatty acids and amino acids, as well as glucose.
What is the fuel for the citric acid cycle?
Acetyl CoA, GDP, Pi, NAD+, and FAD
What can be synthesized from oxaloacetate?
Aspartate (generated by transamination).
Why are the ATP's generated from ox/phos NADH and FADH2 approximate?
Because ATP is only generated indirectly from NADH and FADH2, through setting up the proton pumps for ATP synthase.
What does citrate give rise to?
Carbon for fatty acid synthesis, and control of glycolysis (via PFK)
What four intermediates of the cycle are important for synthesis of other cell constituents?
Citrate, α-ketoglutarate, succinyl CoA, and oxaloacetate.
Where in the cell does the citric acid cycle occur?
In the matrix of the mitochondria.
Where in the cell does ox/phos occur?
Inner mitochondrial membrane of the cell
How many ATP's are generated through ox/phos during the oxidation of NADH?
NADH yields about 3 ATP/NADH.
How is the proton gradient in ox/phos generated?
NADH-CoQ reductase, CoQ-cytochrome c reductase, and cytochrome oxidase pump H+ ions out of the matrix of the mitochondria into the inner membrane space generating a proton gradient.
The oxidation of one mole of glucose via glycolysis and the c.a.c produces ~30 moles of ATP.
Only if you count the GTP's as ATP's. (freebie from groseclose!)
What is P50? (hint: Hb!)
P50 is the pO2 at which half of the available binding sites are occupied.
What are the citric acid cycle's anabolic functions?
Produces starting materials for the synthesis of glucose, amino acids, fatty acids, heme, and many other cell constituents.
How does the uncoupler of ox/phos work?
They interfere with the phosphorylation of ADP to ATP by allowing protons to pass through the IMM anywhere, not just through the ATP synthase, collapsing the proton gradient.
What are the other names for the citric acid cycle?
Tricarboxylic Acid Cycle (TCA) and Kreb's cycle.
How does P50 change with a right shift? (hint: Hb!)
With a right shift, O2 unloading is increased. P50 is increased.
What is pyruvate carboxylases' allosteric effector?
acetyl CoA
Where within the cell does ox/phos occur?
inner mitchondrial membrane
