Pyruvate, gluconeogenesis, AA metabolism Flashcards
What is the Cori cycle?
Anaerobic respiration in animals
Describe the Cori cycle
Glucose to pyruvate through glycolysis in the muscles
Pyruvate to lactate using lactate dehydrogenase (NADH–>NAD+)
Lactate transporter in the bloodstream to the liver
Lactate to pyruvate using lactate dehydrogenase
Pyruvate to glucose through gluconeogenesis
Where does the link reaction occur?
In the mitochondrial matrix
Describe link reaction
Pyruvate + CoA –> acetyl CoA + CO2 (NAD –> NADH)
Uses pyruvate dehydrogenase
Acetyl CoA enters Krebs cycle
What inhibits pyruvate dehydrogenase complex?
Acetyl CoA and NADH allosterically
Acetyl CoA, NADH, ATP by phosphorylation
What activates pyruvate dehydrogenase complex?
Pyruvate and insulin by de-phosphorylation
Where does the tricarboxylic acid cycle occur?
Mitochondrial matrix
Describe the Krebs cycle
Oxaloacetate + acetyl CoA –> citrate (citrate synthase)
Citrate –> isocitrate
Isocitrate –> alpha ketoglutarate + CO2 (isocitrate dehydrogenase) (NAD+–>NADH)
Alpha ketoglutarate –> succinyl CoA + CO2 (alpha ketoglutarate dehydrogenase) (NAD+–>NADH)
Succinyl CoA –> Succinate (GDP–>GTP–>ATP)
Succinate –> fumarate (FAD–>FADH2)
Fumarate –> Malate
Malate –> Oxaloacetate (NAD+–>NADH)
How is citrate synthase activated?
AMP
How is citrate synthase inhibited?
ATP
How are isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase activated?
Ca2+
How are isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase inhibited?
ATP and NADH
Where does the electron transport chain take place?
Across the inner membrane of the mitochondria (between the matrix and the inter membrane space)
Describe the electron transport chain
NADH and FADH2 donate electrons and protons.
Electrons donated to the ETC, they move down the ETC by a series of REDOX reactions.
The energy is used to pump protons against the concentration gradient across the membrane into the inter-membrane space.
Protons move down the electrochemical gradient by chemiosmosis through ATP synthase forming ATP.
Protons and electrons react with oxygen to form water to maintain the electrochemical gradient
What is the phosphate pentose pathway?
Pathway that forms NADH
What is the product of phosphate pentose pathway used for?
NADH is used in reductive biosynthetic pathways e.g. fatty acid synthesis
Where does the phosphate pentose pathway occur?
In the cytosol
What enzyme is used in the 1st step of the phosphate pentose pathway?
Glucose-6-phosphatase dehydrogenase
What is gluconeogenesis?
The formation of glucose in the liver from non-carbohydrate substrates
What are the substrates for gluconeogenesis?
Pyruvate (from alanine or lactate) or dihydroxyacetone-p from glycerol
How is pyruvate formed from alanine or lactate?
Alanine is transaminated by alanine aminotransferase to pyruvate.
Lactate converted to pyruvate using lactate dehydrogenase
Describe gluconeogenesis?
They enter as pyruvate.
Pyruvate is converted into phosphenolpyruvate in 2 steps catalysed by pyruvate carboxylase and PEP carboxykinase.
Glycolysis is then reversed to form glucose
What enzymes are used in the irreversible steps of gluconeogenesis?
Pyruvate carboxylase and PEP carboxykinase used to convert pyruvate into phosphenolpyruvate
Fructose-1,6-bisphosphatase used to convert fructose-1,6-bisp to fructose-6p.
Glucose-6-phosphatase used to convert glucose-6-p into glucose
How is gluconeogenesis activated?
Glucagon
What activates pyruvate carboxylase?
Acetyl CoA
What are essential amino acids?
Amino acids essential for survival that our bodies cannot make
What are non-essential amino acids?
Needed for survival but our bodies can make them
What is a keto-acid?
AA without amino group
What is transamination?
The formation of an AA from a ketoacid by another AA donating the amino group
What enzymes are used in transamination?
Aminotransferase
What is phenylketonuria?
Lack of phenylalanine hydrolase.
Phenylalanine cannot be converted to tyrosine.
Phenylalanine saturates the blood brain barrier so other molecules cannot cross
Describe the process of AA catabolism
AA donates amino group to convert alpha-ketoglutarate into glutamate.
Glutamate can be deaminated.
The ketoacids can enter TCA cycle
What are glycolic ketoacids?
Enter TCA cycle
What are ketogenic ketoacids?
Enter ketone synthesis
What is the fate of serine after AA catabolism?
Transaminated to form the veto from of 3-phosphoglycerate which can enter glycolysis to prom pyruvate.
What is the fate of glutamate after AA catabolism?
Transaminated into alpha-ketoglutarate which can enter TCA cycle
