Exam 4 Flashcards
Where does the citric acid cycle take place in the cell?
Mitochondria
In the presence of oxygen, pyruvate is converted to this
acetyl-CoA
a large, multi-subunit enzyme complex that links glycolysis and the citric acid cycle under aerobic conditions
PDH (pyruvate dehydrogenase)
provides a flexible linker between active sites within the pyruvate dehydrogenase complex
lipoamide
causes the disease Beriberi
deficiency in vitamin thiamine
the activated form of acyl groups and the fuel for the citric acid cycle
acetyl CoA
What are the steps involved in the conversion of pyruvate to acetyl CoA
- Decarboxylation
- Oxidation
- Transfer to CoA
Which of the following functions as a “flexible swinging arm” when it transfers the reaction intermediate from one active site to the next?
lipoamide
PDH phosphatase deficiency results in this
chronic elevated plasma lactate
Which PDH cofactor is affected by mercury and arsenide compounds?
Lipoamide
What are the three enzyme subunits in the PDH complex and the reactions they catalyse
E1: the PDH component and catalyzes the oxidative decarboxylation of pyruvate.
E2: is called dyhydrolipoyl transacetylase and catalyzes the transfer of an acetyl group to coenzyme A.
E3: The third enzyme subunit is dyhydrolipoyl dehydrogenase and catalyzes the regeneration of the oxidized form of lipoamide
What are the five essential cofactors for PDH?
TPP, Lipoic Acid, FAD, NAD+, CoA
How are the three active sites of PDH linked?
the long, flexible arm of the E2 subunit acts like a long robotic arm and carries the substrate from active site to active site
What are the two advantages that are derived from the coordinated actions of the three enzymes in the PDH complex?
The proximity of one enzyme to another enzyme increases the overall reaction rate and minimizes side reactions
What is the key means of regulation of PDH
The inactive form of PDH is the phosphorylated form of the E1 component. PDH phosphatase activates PDH by removing the phosphoryl group and PDH kinase phosphorylates and inactivates it again when the energy charge is high.
The formation of acetyl CoA limits the cell’s use of it to which two fates?
The oxidative decarboxylation of pyruvate to form acetyl CoA is an irreversible step in animals, so pyruvate cannot be reformed. It can either be completely oxidized to CO2 in the citric acid cycle or it can be incorporated into lipids.
the product found by the condensation of oxaloacetate and acetyl CoA
citrate
the citric acid cycle intermediate is at both the beginning and the end of the citric acid cycle
oxaloacetate
the product of the complete oxidation of carbon in the citric acid cycle
carbon dioxide
carbons from carbs enter the citric acid cycle in the form of
acetyl CoA
When is the citric acid cycle inhibited
high energy conditions
the first citric acid cycle intermediate to be oxidized
isocitrate
organisms that can convert fat into sugar use the ____ cycle
glyxolyate
a mutation in the active site of succinyl CoA synthetase where His is converted into a Lysine would result in
the loss of a sucking phosphate intermediate