Unit 9 Flashcards
Explain what is meant by the phrase:pyruvate dehydrogenase complex the reaction it catalyses,its importance and its cellular location Hint:
your answer should also mention two metabolic pathways.
pyruvate that is generated from glycolysis is converted to acetyl CoA
happens in mitochondrial matrix
deficiencies in the coenzymes or any alteration in enzyme activities can result in diseases like beriberi.
PDH is also a site of arsenic poisoning.
Compare and contrast the mechanism of
arsenic poisoning in the glycolytic pathway and the pyruvate dehydrogenase complex.
similarity- 1) interferes with enzyme activity 2) cells witness reduced ATP reduction
Difference- In glycolysis it is pentavlent arsenate, acts as inhibitor of phosphate
In pyruvate trivalent arsenate enhibits enzyme by binding to site on lipoic acid
Explain one regulatory mechanism that exercising muscle may employ to
affect the pyruvate dehydrogenase complex and how the result of this mechanism would be beneficial to exercising muscle.
calcium is a strong activator of PDH phosphatase, which stimulates E1 activity
release of Ca2+ stimulates PDC which produced energy
A high energy state in the cell is usually indicated by high concentrations of ATP, acetyl CoA, and NADH. Explain how the components of this high energy state may affect the activity of pyruvate dehydrogenase
and the generation of energy
kinase is allosterically activated by 3 things
Therefore in high energy PDC turned off
CoA and NADH allosterically inhibit the dephosphorylated form of E1
The human disease beriberi is caused by a deficiency of thiamine in the diet. People with severe beriberi have higher than normal levels of pyruvate in their blood and urine. Explain this observation in terms of a
particular enzymatic reaction.
defiency in vitamin b1 causes decrease in pyruvate dehydrogenase activity
cause increase pyruvate and decrease in Acetyl CoA that enters TCA cycle which decreases ATP
What is the cellular location of TCA cycle
in eukaryotes how many chemical reactions are used in the TCA cycle when converting acetyl CoA to oxaloaceta the, and what is the essential purpose of this series of
reactions in terms of glucose catabolism?
Mitochondria
8 chemical reactions
purpose- important role in glucose catabolism due to carbon skeleton of some amino acids. provides building blocks for amino acid and heme
The synthesis of citrate from acetyl CoA and oxaloacetate is a biosynthetic reaction. What is the energy source that drives this reaction and what observation about this reaction would support this?
citrate synthase
equilibrium in direction of citrate synthase which supports it as energy source
Mutations can occur in humans where an enzyme can have no activity or much less activity and this leads to various diseases. However, mutations in enzymes of the TCA cycle are rarely seen. Why is this?
Die quickly
The phrase: ‘substrate phosphorylation’ is often given to a particular type
of reaction. Explain this phrase and give one example from both glycolysis
and the TCA cycle where this reaction occurs.
synthesis of ATP from ADP by high-energy phosphate bonds
bonds are completed by rxns that have ADP as substrate produce ATP
glycolysis- ATP production when 1,3 bisphophoglycerate is converted to ATP
TCA cycle- GDP + Pi forms GTP
The phrase: ‘oxidative decarboxylation’ is given to a particular type of enzymecatalysed reaction. Explain this phrase and support your
explanation with a particular example from
the TCA cycle Hint: include in your answer any coenzymes that may participate in this reaction.
oxidation reactions that contains a carboxylate group that is removed to create CO2
Happens in TCA when alpha-ketoglutarate is converted to succinyl CoA.
coenzymes: are thiamine pyrophosphate, lipoid acid, FAD, NAD+, and CoA.
Explain how uncoupling proteins achieve their effect and which tissue uses these proteins. What is one example of a synthetic chemical that has the same effect as an uncoupling protein?
by ‘proton leak’- allows protons to re-enter mitochondrial matrix without energy captured as ATP
brown adipocytes of mammals
aspirin
