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27 Cards in this Set

  • Front
  • Back
What metabolic reactions take place in the mitochondria?
-B-oxidation of FA
Describe the mito from outside to inside.
Outer mito membrane --> Intermembrane space --> Inner mito membrane --> mitochondrial matrix
What are key features of the OMM?
Has porins which form large aqueous channels that allow passage of molecules such as NADH, FADH2 and molec with weight < 10,000 g/mol
What are key features of IMM?
-80% ptn by weight
-has Cardiolipin which thickens the mb and makes it impermeable to ions
-Has transport ptns that are part of ETC (ATP synthase)
-Forms cristae which inc SA to maximize ATP production
Key features of the mitochondrial matrix?
-7 of 8 CAC enz
-B-oxid of FA
-Enz used for oxid of certain aa
-enz of low MW, DNA, RNA etc
WHat is the evidence for the endosymbyosis theory for mito?
-Double mb structure (OMM and IMM)
-Circular DNA genome
-Mito ptn synthesis inhibited by chloramphenicol (which also inhibits bacterial ptn synthesis) but does not inhibit cytoplasmic ptn synthesis
How is pyruvate transported into the mito?
Pyruvate translocase
-Acts as an H+ symport
Carries pyruvate and H+ in (even though pyruvate is going against its [gradient])
What is an example of an antiport ptn?
ATP/ADP exchange ptn
-transmb potential-cyclical process
-ATP is more negative than ADP and mito is more negative than cytosol so ATP is expelled to cyto. and ADP is brought into mito
What does the ATP synthase do?
Transports H+ to P ADP to ATP
What are the 3 subunits of PDC and their functions?
E1: Pyruvate Dehydrogenase
E2: Dihydrolipoyl Transacetylase
E3: Dihydrolipoyl Dehydrogenase
What are the accessory ptns in the PDC and their functions?
-E3 Binding protein: ptn that binds E3 to E2
-Pyruvate deydrogenase Kinase (PDK): P E1, which inactivates it
-Pyruvate dehydrogenase Phosphatase (PDP): reverses the effects of PDK on PDC
What does the PDC do?
Where does this take place?
Pyruvate--> Acetyl CoA
Mitochondrial matrix
What is Beriberi?
Thiamine deficiency, unable to convert pyruvate to Acetyl CoA
What are the cofactors of the PDC and their functions?
-TPP: bound to E1. Decarboxylates pyruvate to get hydroxyethyl-TPP carbanion
-Lipoic Acid: covalently linked to E2 (lipoamide). Accepts the hydroxyethyl carbanion from TPP as an acetyl gp
-Coenzyme A (CoA): Substrate for E2. Accepts acetyl gp from E2
-FAD: bound to E3. Reduced by lipoamide
-NAD+: Substrate for E3. Reduced by FADH2
What is the overall rxn of PDC?
Pyruvate + CoA-SH + NAD+ --> Acetyl CoA + NADH + H+ + CO2
What is step 1 of PDC?
-Covalent catalysis btw E1, E2 and substrate
-Nuc attack on pyruvate
-Decarboxylation facilitated by TPP
What is step 2 of PDC?
-Hydroxyethyl-TPP makes carbanion which does a nuc attack on lipoamide of E2
-Transfer a 2C gp from E1 to E2 and oxidizes a C to a COOH
-Prod: acetyl-dihydrolipoamide (has a thioester linkage, high E)
What is step 3 of PDC?
-Transesterification catalyzed by E2
-get Acetyl CoA
What is step 4 of PDC?
-Disulfide exchange
-E3 oxidizes E2's sulfhydryl gps to regenerate the lipoamides diS gp
What is step 5 of PDC?
-Reform diS gp in E3
-reduction of FAD and then NAD+
What does arsenite affect?
-PDC and a-Ketogluterate-DH-complex
-Attacks lipoamide moiety of E2 and forms bidentate adduct which stops PDC and a-KDC
What is arsenate and what does it do?
-Phosphate analog
-competes with phosphates in all rxn involving phosphate
-Affects GAP-DH, forms another intermediate .: lose 1 ATP from glycolysis
=> not as bad as shutting down PDC tho (like arsenite does)
What are teh mechanistic advantages of multienzyme complexes?
1) Rxn rate inc because distance btw active sites dec
2) Metabolic interm are channeled btw active sites
-Reduces side rxns
-protects labile intermediates
3) Coordinate control of enzyme activities: inhibit one enz, whole complex shuts down (easier to control)
How is pyruvate regulated?
-Lactate DH
What is the Warburg Effect?
Cancer cells downregulate PDC and utilize Lactate DH.
Use only glycolysis instead of glycolysis + oxid P
What can Acetyl CoA be used for?
Only CAC or FA synthesis (can't go back to glucose .: committed step)
What are the 2 methods of regulatiokn of PDC?
-Product inhibition: NADH inhibits rxn 5 and Acetyl-CoA inhibits rxn 3
-Covalent Modification:
->PDK: P E1 and inhibits the complex. PDK activated by NADH and Acetyl-CoA. PDK inhibited by: pyruvate, ADP, Ca2+
->PDP: deP E1 so that it can be active. PDP activated by Ca2+ and Mg2+