BCH 451: EXAM 3 QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
where does glycolysis occur
cytoplasm
where does the citric acid cycle occur
mitochondrial matrix, except for succinate dehydrogenase in inner membrane
where does oxidative phosphorylation occur
mitochondrial inner membrane
Conversion of Pyruvate to Acetyl-CoA Decarboxylation #1
Pyruvate translocate actively transports pyruvate into the mitochondria
Oxidative decarboxylation of pyruvate
lose CO2, generate NADH
Function of CoA is to accept and carry
acetyl groups
Structure of Lipoyllysine: Prosthetic groups strongly bound to
protein
Structure of Lipoyllysine: Lipoate can serve as both _______ and ___________
electron (hydrogen) carrier and as acyl carrier
TPP
carries active acetaldehyde
Lipoate
carries electrons and acetyl
,CoA
carries acetyl
NADH and FADH2
carries electrons
Step 1 CAC: Carbon Carbon bond formation by condensation of Acetyl-CoA and
Oxaloacetate
- Condensation of acetyl-CoA and oxaloacetate by citrate synthase
- Only carbon carbon bond formation
- Rate limiting step, activity depends on oxaloacetate concentration
- Highly thermodynamically favorable/irreversible, regulated by substrate availability and
product inhibition
Citrate Synthase's Induced Fit: Open conformation
free enzyme doesn't have binding site for acetyl-CoA
Citrate Synthase's Induced Fit: Closed conformation
binding of OAA create binding for acetyl CoA, reactive carbanion protected
Aconitase Structure: Iron sulfur center
water removal and addition are catalyzed (sensitive to oxidative stress)
Aconitase Structure: Stereospecific
only R-isocitrate produced by aconitase, three point attachment to active site
Step 3 CAC: Oxidative Decarboxylation #2
- Oxidative decarboxylation via isocitrate dehydrogenase to ketone, transfers hydride to
NAD or NADP
- Cytosolic isozyme uses NADP as cofactor
, - Lose carbon from oxaloacetate (not acetyl CoA) as CO2
- Mn2+ stabilize transient enol
- Highly thermodynamically favorable/irreversible
- Regulated by product inhibition and ATP
Step 4 CAC: Oxidative Decarboxylation #3
- Last oxidative decarboxylation via alpha ketoglutarate dehydrogenase
- Net full oxidation of all carbons of glucose after two turns of cycle
- Carbons not directly from glucose, but from oxaloacetate
- Succinyl CoA higher energy thioester bond
- Highly thermodynamically favorable/irreversible
- Regulated by product inhibition
Step 5 CAC: Generation of GTP Through Thioester
- Substrate level phosphorylation via succinyl-CoA synthetase
- Goes through a phospho-enzyme intermediate
- Produces GTP, can be converted to ATP
- Slightly thermodynamically favorable/reversible
- Product concentration kept low to pull forward
Step 6 CAC: Oxidation of an Alkane to Alkene
- Bound to mitochondrial inner membrane, part of Complex II in the electron transport
chain
- Oxidation of the alkane to alkene requires FAD (covalently bound)
- Near equilibrium/reversible
- Product concentration kept low to pull forward
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
where does glycolysis occur
cytoplasm
where does the citric acid cycle occur
mitochondrial matrix, except for succinate dehydrogenase in inner membrane
where does oxidative phosphorylation occur
mitochondrial inner membrane
Conversion of Pyruvate to Acetyl-CoA Decarboxylation #1
Pyruvate translocate actively transports pyruvate into the mitochondria
Oxidative decarboxylation of pyruvate
lose CO2, generate NADH
Function of CoA is to accept and carry
acetyl groups
Structure of Lipoyllysine: Prosthetic groups strongly bound to
protein
Structure of Lipoyllysine: Lipoate can serve as both _______ and ___________
electron (hydrogen) carrier and as acyl carrier
TPP
carries active acetaldehyde
Lipoate
carries electrons and acetyl
,CoA
carries acetyl
NADH and FADH2
carries electrons
Step 1 CAC: Carbon Carbon bond formation by condensation of Acetyl-CoA and
Oxaloacetate
- Condensation of acetyl-CoA and oxaloacetate by citrate synthase
- Only carbon carbon bond formation
- Rate limiting step, activity depends on oxaloacetate concentration
- Highly thermodynamically favorable/irreversible, regulated by substrate availability and
product inhibition
Citrate Synthase's Induced Fit: Open conformation
free enzyme doesn't have binding site for acetyl-CoA
Citrate Synthase's Induced Fit: Closed conformation
binding of OAA create binding for acetyl CoA, reactive carbanion protected
Aconitase Structure: Iron sulfur center
water removal and addition are catalyzed (sensitive to oxidative stress)
Aconitase Structure: Stereospecific
only R-isocitrate produced by aconitase, three point attachment to active site
Step 3 CAC: Oxidative Decarboxylation #2
- Oxidative decarboxylation via isocitrate dehydrogenase to ketone, transfers hydride to
NAD or NADP
- Cytosolic isozyme uses NADP as cofactor
, - Lose carbon from oxaloacetate (not acetyl CoA) as CO2
- Mn2+ stabilize transient enol
- Highly thermodynamically favorable/irreversible
- Regulated by product inhibition and ATP
Step 4 CAC: Oxidative Decarboxylation #3
- Last oxidative decarboxylation via alpha ketoglutarate dehydrogenase
- Net full oxidation of all carbons of glucose after two turns of cycle
- Carbons not directly from glucose, but from oxaloacetate
- Succinyl CoA higher energy thioester bond
- Highly thermodynamically favorable/irreversible
- Regulated by product inhibition
Step 5 CAC: Generation of GTP Through Thioester
- Substrate level phosphorylation via succinyl-CoA synthetase
- Goes through a phospho-enzyme intermediate
- Produces GTP, can be converted to ATP
- Slightly thermodynamically favorable/reversible
- Product concentration kept low to pull forward
Step 6 CAC: Oxidation of an Alkane to Alkene
- Bound to mitochondrial inner membrane, part of Complex II in the electron transport
chain
- Oxidation of the alkane to alkene requires FAD (covalently bound)
- Near equilibrium/reversible
- Product concentration kept low to pull forward
