Review 2: TCA Cycle Flashcards
Through what process are triglycerides converted into acetyl coA?
beta oxidation of fatty acids
What can acetyl CoA go on to become?
1) energy via TCA
2) ketone bodies
3) fatty acids; cholesterol
What 3 things can produce acetyl coA?
1) pyruvate
2) fatty acids
3) amino acids
What enzyme is responsible for converting pyruvate into acetyl CoA?
PDH (pyruvate dehydrogenase)
What 3 vitamin cofactors are required for PDH function?
1) Thiamine (B1)
2) Riboflavin (B2)
3) Niacin (B3)
The most common form of pyruvate dehydrogenase deficiency is caused by mutations in the ___ alpha gene (X-linked)
E1
Children with PDH deficiency have elevated serum levels of ________, _______, and ________.
lactate, pyruvate, and alanine
cannot shuttle pyruvate into TCA cycle
Each cycle of the TCA generates ___ ATP and ___ GTP
9; 1
reoxidation of 3 NADH, 1 FADH2, and 1 GTP
What is the ATP conversion rate of reoxidizing NADH? FADH2?
NADH 2.5
FADH2 1.5
What method of enzyme regulation is primarily responsible for the fine control of TCA enzymes?
allosteric regulation
higher conc of ADP and Ca++ __________ TCA cycle
stimulates
higher conc of ATP, GTP, and NADH (high energy) _______ TCA cycle.
inhibits
True or False: TCA cycle intermediates can be replenished by anaplerotic (intermediate) reactions
True
Aspartate can feed into the TCA cycle as what?
oxaloacetate
glutamate can feed into the TCA cycle as what?
alpha ketoglutarate
propionyl coA (from valine and isoleucine) can feed into the TCA cycle as what?
succinyl CoA
Aspartate, phenylalanine, tyrosine can feed into the TCA cycle as what?
fumarate
Define gluconeogenesis
synthesis of glucose from noncarbohydrate precursors
What condition stimulates gluconeogenesis?
low blood glucose
Where does gluconeogenesis take place?
liver and kidney
During gluconeogenesis, pyruvate is converted into ___________________
phosphoenolpyruvate (in a 2 step process via oxaloacetate) this is the ACTIVATED form of pyruvate
What two substances are involved in the activation of pyruvate into PEP?
bicarbonate and cofactor biotin
What is the Cori Cycle?
glucose-lactate cycle
Where does the Cori cycle occur?
RBCs and skeletal muscle
Where does the Alanine cycle occur?
skeletal muscle
Does gluconeogeneis produce or consume ATP?
CONSUME
True or false: gluconeogenesis from amino acids requires more ATP (which is used for ureagenesis)
true
What serves as the major source of ATP for gluconeogenesis during fasting?
Oxidation of fatty acids
What are the 4 enzymes that are required to reverse the 3 irreversible steps of glycolysis?
1) pyruvate carboxylase (in the mitochondria)
2) Phosphoenolpyruvate carboxykinase (cytoplasm)
3) Fructose 1,6 bisphosphatase (cytoplasm)
4) Glucose 6-phosphatase (cytoplasm)
The lack of which enzyme causes the accumulation of pyruvate in the plasma (which is then converted to lactate)
Pyruvate carboxylase
What reaction does pyruvate carboxylase catalyze?
pyruvate to oxaloacetate
What is von Gierke disease?
deficiency of glucose 6-phosphatase
inherited autosomal recessive - glycogen storage disease
What reaction cannot happen in patients with von Gierke disease?
gluconeogenesis (glucose 6-phosphatase cannot convert glucose 6-phophate into glucose for the brain to use)
What happens to the liver in patients with von Gierke disease?
enlarges due to the accumulation of glycogen and fat in the liver (elevated serum uric acid and lactate)
Ethanol metabolism can cause ___________ because high NADH OPPOSES gluconeogenesis
hypoglycemia
Ethanol metabolism ___________ the NADH/NAD ratio
increases
high levels of NADH promotes the conversion of pyruvate and oxaloacetate into ________ and _______
lactate and malate
Increased NADH leads to lactate _______
formation
decreased NADH leads to _______ lactate formation
decreased
