EXAM 3 BIOC405 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Pyruvate fate in hypoxic conditions, cells without mitochondria, or anaerobic
organisms
pyruvate is reduced in the cytoplasm to regenerate NAD+ for glycolysis in
pyruvate fate in cells with oxygen and mitochondria
pyruvate is transported into the mitochondria for aerobic respiration
Inner mitochondrial membrane purpose
Generates ATP
Mitochondrial matrix purpose
Pyruvate oxidation and citric acid cycle
Cells without mitochondria
Bacteria, cells in the sense of the inner eye, red blood cells
Pyruvate Dehydrogenase (PDH) complex purpose
catalyzes the oxidative decarboxylation of pyruvate and its conversion to acetyl-CoA
Pyruvate to Acetyl-CoA reaction
Pyruvate + NAD+ + CoA-SH => Acetyl-CoA + NADH + CO2
Thiamine pyrophosphate (TPP) location
tightly bound to E1
Thiamine pyrophosphate (TPP) function
decarboxylates pyruvate, yielding hydroxyethyl-TPP
,Lipoid acid (lipoamide) location
covalently bound to E2 via lysine ("swinging arm")
Lipoid acid (lipoamide) function
accepts hydroxyethyl carbanion from TPP as acetyl group
Coenzyme A (CoA) location
Dissociable substrate for E2
Coenzyme A (CoA) function
accepts acetyl group from lipoamide
Flavin adenine dinucleotide (FAD) location
Tightly bound to E3
Flavin adenine dinucleotide (FAD) function
Accepts a pair of electrons from reduced lipoamide
nicotinamide adenine dinucleotide (NAD+) location
Dissociable substrate for E3
nicotinamide adenine dinucleotide (NAD+) function
Accepts a pair of electrons from reduced FADH2
Reaction 1 of the PDH complex
Decarboxylation of pyruvate using TPP as a cofactor causing the formation of
hydroxyethyl-TPP
Reaction 2 of the PDH complex
Oxidation to acetyl group bound to lipoamide cofactor by cofactor E2 (dihydrolipoamide
transacetylase)
Reaction 3 of the PDH complex
,Transfer of acetyl group from acetyl-dihydrolipoamide to CoA to form Acetyl-CoA by
cofactor E2 (dihydrolipoamide transacetylase)
Reaction 4 of the PDH complex
Re-oxidation of the dihydrolipoamide to regenerate E2
Reaction 5 of the PDH complex
Transfer of electrons to NAD+ and FAD+
FAD+ => FADH in reaction 5 of the PDH reactions
Accepts 1 or 2 H+ ions at different binding sites
NAD+ => NADH in reaction 5 of the PDH reactions
Accepts 1 H2 molecule at the same binding site
Regulators of the PDH Complex
allosterically via phosphorylation of the PDH complex and transcription of acetyl-CoA
and NADH which provides feedback inhibition
3 enzymes of the PDH complex
E1: pyruvate dehydrogenase
E2: dihydrolipoamide transacetylase
E3: dihydrolipoamide dehydrogenase
5 cofactors of the PDH complex
Thiamine pyrophosphate (vitamin B1), Lipoic acid/lipoamide, Coenzyme A (vitamin B5),
flavin adenine dinucleotide (vitamin B2), NAD+ (vitamin B3)
4 types of molecules that the citric acid extracts energy from
carbohydrates, lipids, proteins, and metabolites (ex. amino acids)
common entry molecule into the citric acid cycle
, acetyl-CoA
Citric acid cycle function
extract energy from acetyl-CoA in the form of electrons and feed these into the ETC for
oxidative phosphorylation
Citric acid cycle reaction
Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 2 H2O => 2 CO2 + 3 NADH + FADH2 +
GTP + 2H+ + CoA
Step 1 of Citric Acid Cycle
Acetyl-CoA + Oxaloacetate --> Citrate
Uses citrate synthase enzyme
H2O --> CoA
Step 2 of Citric Acid Cycle
Citrate <--> Isocitrate
Uses aconitase enzyme
H2O <--> H2O
Step 3 of Citric Acid Cycle
Isocitrate --> α-ketoglutarate
Uses isocitrate dehydrogenase
NAD(P)+ --> NAD(P)H + CO2
Step 4 of Citric Acid Cycle
alpha-ketoglutarate (5C) + NAD+ + CoA --> succinyl CoA (4C) + CO2 + NADH
by alpha-ketoglutarate dehydrogenase, which requires CoA-SH and NAD+
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Pyruvate fate in hypoxic conditions, cells without mitochondria, or anaerobic
organisms
pyruvate is reduced in the cytoplasm to regenerate NAD+ for glycolysis in
pyruvate fate in cells with oxygen and mitochondria
pyruvate is transported into the mitochondria for aerobic respiration
Inner mitochondrial membrane purpose
Generates ATP
Mitochondrial matrix purpose
Pyruvate oxidation and citric acid cycle
Cells without mitochondria
Bacteria, cells in the sense of the inner eye, red blood cells
Pyruvate Dehydrogenase (PDH) complex purpose
catalyzes the oxidative decarboxylation of pyruvate and its conversion to acetyl-CoA
Pyruvate to Acetyl-CoA reaction
Pyruvate + NAD+ + CoA-SH => Acetyl-CoA + NADH + CO2
Thiamine pyrophosphate (TPP) location
tightly bound to E1
Thiamine pyrophosphate (TPP) function
decarboxylates pyruvate, yielding hydroxyethyl-TPP
,Lipoid acid (lipoamide) location
covalently bound to E2 via lysine ("swinging arm")
Lipoid acid (lipoamide) function
accepts hydroxyethyl carbanion from TPP as acetyl group
Coenzyme A (CoA) location
Dissociable substrate for E2
Coenzyme A (CoA) function
accepts acetyl group from lipoamide
Flavin adenine dinucleotide (FAD) location
Tightly bound to E3
Flavin adenine dinucleotide (FAD) function
Accepts a pair of electrons from reduced lipoamide
nicotinamide adenine dinucleotide (NAD+) location
Dissociable substrate for E3
nicotinamide adenine dinucleotide (NAD+) function
Accepts a pair of electrons from reduced FADH2
Reaction 1 of the PDH complex
Decarboxylation of pyruvate using TPP as a cofactor causing the formation of
hydroxyethyl-TPP
Reaction 2 of the PDH complex
Oxidation to acetyl group bound to lipoamide cofactor by cofactor E2 (dihydrolipoamide
transacetylase)
Reaction 3 of the PDH complex
,Transfer of acetyl group from acetyl-dihydrolipoamide to CoA to form Acetyl-CoA by
cofactor E2 (dihydrolipoamide transacetylase)
Reaction 4 of the PDH complex
Re-oxidation of the dihydrolipoamide to regenerate E2
Reaction 5 of the PDH complex
Transfer of electrons to NAD+ and FAD+
FAD+ => FADH in reaction 5 of the PDH reactions
Accepts 1 or 2 H+ ions at different binding sites
NAD+ => NADH in reaction 5 of the PDH reactions
Accepts 1 H2 molecule at the same binding site
Regulators of the PDH Complex
allosterically via phosphorylation of the PDH complex and transcription of acetyl-CoA
and NADH which provides feedback inhibition
3 enzymes of the PDH complex
E1: pyruvate dehydrogenase
E2: dihydrolipoamide transacetylase
E3: dihydrolipoamide dehydrogenase
5 cofactors of the PDH complex
Thiamine pyrophosphate (vitamin B1), Lipoic acid/lipoamide, Coenzyme A (vitamin B5),
flavin adenine dinucleotide (vitamin B2), NAD+ (vitamin B3)
4 types of molecules that the citric acid extracts energy from
carbohydrates, lipids, proteins, and metabolites (ex. amino acids)
common entry molecule into the citric acid cycle
, acetyl-CoA
Citric acid cycle function
extract energy from acetyl-CoA in the form of electrons and feed these into the ETC for
oxidative phosphorylation
Citric acid cycle reaction
Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 2 H2O => 2 CO2 + 3 NADH + FADH2 +
GTP + 2H+ + CoA
Step 1 of Citric Acid Cycle
Acetyl-CoA + Oxaloacetate --> Citrate
Uses citrate synthase enzyme
H2O --> CoA
Step 2 of Citric Acid Cycle
Citrate <--> Isocitrate
Uses aconitase enzyme
H2O <--> H2O
Step 3 of Citric Acid Cycle
Isocitrate --> α-ketoglutarate
Uses isocitrate dehydrogenase
NAD(P)+ --> NAD(P)H + CO2
Step 4 of Citric Acid Cycle
alpha-ketoglutarate (5C) + NAD+ + CoA --> succinyl CoA (4C) + CO2 + NADH
by alpha-ketoglutarate dehydrogenase, which requires CoA-SH and NAD+
