Biochemistry-Glycolysis III Flashcards
How does NADH get to the electron transport chain?
Malate Aspartate Shuttle System. The 2 NADH from glycolysis reduce oxaloacetate to malate. Malate inters the mitochondrial matrix from the cytosol where it is oxidized by NAD and NADH is formed within the cytosol.
How does oxaloacetate in the mitochondrial matrix get back into the cytosol?
Transamination to form aspartate by glutamate. Aspartate exits the matrix and enters the cytosol. alpha-ketoglutarate then catalyzes another transamination of aspartate to form oxaloacetate.
Why are most mitochondrial membrane transporters anti ports?
Swapping one solute for another prevents accumulation of solute in the matrix or in the cytosol.
What determines the direction lactate dehydrogenase runs?
NADH/NAD ratio in this reaction.
What tissues use lactate as a fuel? How do they do it?
Liver, resting muscle and heart. The liver uses gluconeogenesis. Resting muscle and heart reverse the lactate dehydrogenase reaction. Lactate -> Pyruvate -> Acetyl CoA -> CO2
Why do your muscles really start to burn after climbing the stairs out of the subway for a minute straight?
You spend the subway ride sitting with little blood flow to skeletal muscle. When you hit the stairs, your muscles need ATP, but blood flow is not sufficient enough to maintain aerobic respiration. Consequently, pyruvate and NADH build up. NADH reduces pyruvate to lactic acid. Lactic acid leaves the cell and causes muscle “burn”.
What is the anaerobic threshold?
Aerobic respiration is maxed out due to activity, pyruvate accumulates and lactic acid production increases.
What tissues depend on anaerobic glycolysis?
Red cells, white blood cells, lens of the eye, kidney medulla and exercising muscle
How does the heart protect itself from muscle cramps?
Myocardium maintains a high concentration of NAD in the cytosol, pushing the reaction towards pyruvate when lactate enter. The pyruvate is then completely oxidized to CO2 and H2O.
How is the liver altruistic in metabolism?
Gluconeogenesis. It takes lactate and gives up precious glucose to other tissues.
Why do tumors rely so heavily on glycolysis?
They are replicating so quickly they need the most “powerful” form of cellular respiration and use anaerobic glycolysis. Lactic acid also helps invade tissues.
