Chapter 10.2 Flashcards
Describe the first step of Krebs cycle(Citrate formation)
- acetyl-coA and oxaloacetate undergo a condensation reaction
- > so you remove co enzymeA(CoA-SH) and get citrate
-note the reaction is synthesized by citrate synthase
What enzyme is the rate limiting enzyme of the Krebs cycle
- it is alpha-ketoglutarate dehydrogenase
- >this enzyme results in the formation of carbon dioxide and NADH
What happens during the oxidation of alpha-ketoglutarate
- NADH is formed and CO2 is also released
- > note here that CoA-SH is also added to alpha-ketoglutarate
- this comes to be known as succinyl-coA
- > it has a thioester bond
How does succinyl-coA become succinate
- through the enzyme succinyl-coA synthetase
- > that hydrolyzes the thioester bond of succinyl-coA
-GTP then forms
What is the role of nucleosidediphosphate kinase
-it transfers phosphate group from GTP to ADP to form ATP
Where does fumarate formation take place
- it is when succinate is converted to fumarate
- > this is the only reaction that doesn’t take place in the mitochondrial matrix
- > it takes place in the mitochondrial membrane
- > through succinate dehydrogenase(complex 2)
-note here that FAD is reduced to FADH2
How does malate form
- the enzyme fumurase converts fumurate to malate
- >only L-malate forms in this reaction
What is the last step of the citric acid cycle
- oxaloacetate forms from malate as malate is oxidized
- > through malate dehydrogenase
- > NADH forms here
How does PDH kinase and PDH phosphatase regulate the PDH complex
PDH kinase
- > phosphorylates the complex
- > inhibits the complex
PDH phosphatase
- > dephosphorylates the complex
- > activates the complex
-note the complex is inhibited by ATP, NADH and acetyl coA
What molecules regulate citrate synthase
- ATP/NADH function as allosteric inhibitors of citrate synthase
- citrate also allosterically inhibits citrate synthase
What molecules regulate the isocitrate dehydrogenase
- ATP and NADH inhibit it
- >ADP and NAD+ activate it
What molecules regulate alpha-ketoglutarate dehydrogenase complex
- succinyl-coA/ NADH/ATP inhibits this complex
- note ADP and calcium ions activate the alpha ketoglutarate complex
