Glycolysis Flashcards
Is glycolysis anaerobic or aerobic?
Glycolysis can function aerobically and anaerobically depending on availability of oxygen and ET chain.
How do erythrocytes metabolize glycolysis?
B/c they lack mitochondria, they rely on glucose as their metabolic fuel & metabolize it anaerobically.
How are skeletal muscles able to perform under low oxygen levels?
Ability of glycolysis to provide ATP during intense exercise helps tissues survive anoxic episodes.
Diseases in which enzymes of glycolysis are deficient
Hemolytic anemias
In fast growing cancer cells, glycolysis proceeds at _____?
High rate, forming a lot of PYRUVATEs, which are then reduced to lactate and exported.
What transpires when muscle contracts under anaerobic conditions?
Glycogen disappears, lactate appears
What is the end product of glycolysis of oxygen is involved?
PYRUVATE
What is the price to pay when glycolysis occurs in anaerobic conditions?
Less ATP produced per mole of glucose oxidized
What happens to PYRUVATE formed in anaerobic glycolysis in yeast and other microorganisms?
PYRUVATE is NOT reduced to lactate BUT decarboxylated and reduced to ETHANOL.
All enzymes of glycolysis are…
cytosolic.
Is the conversion of glucose to G6P reversible?
No. It is an irreversible reaction.
What catalyzes the conversion of glucose to G6P?
Hexokinase
How is hexokinase inhibited?
It is inhibited by its product — G6P.
What is an isoenzyme of hexokinase found in liver and pancreatic B-islet cells?
Glucokinase
Function of glucokinase in liver
Remove glucose from hepatic portal blood following a meal, regulating available concentration to peripheral tissues
Function of glucokinase in pancreatic B-islet cells
Detects high concentrations of glucose in portal blood
Increased glycolysis and increased ATP formation lead to…
closure of ATP-K channel, causing membrane depolarization & opening of voltage gated ca2+ channel.
Influx of Ca++ leads to…
Fusion of insulin secretory granules w/ cell membrane & release of insulin
How many ATPs were produced during the substrate level phosphorylation step of glycolysis?
2 ATPs since 2 triose phosphate molecules were created.
Toxicity of arsenic is a result of what?
Competition of arsenate w/ Pi —-> 1-Arseno-3-phosphoglycerate
What products are produced when 1-arseno-3-phosphoglycerate is hydrolyzed?
3-phosphoglycerate without ATP
Under anaerobic conditions, what enzyme catalyzes PYRUVATE to lactate?
Lactate dehydrogenase
What pathway does PYRUVATE follow in aerobic conditions?
PYRUVATE enters mitochondria and gets converted to acetyl coA through oxidative decarboxylation then gets oxidized to CO2 in CAC.
Why does glycolysis in erythrocytes always terminates in lactate?
Subsequent reactions of PYRUVATE oxidation are mitochondrial and erythrocytes do not have mitochondria.
What conditions produce lactate?
vigorous exercise, septic shock, cancer cachexia
Lactate is oxidized to PYRUVATE in what organelle?
mitochondrion
True or False:
Do Liver, kidneys, and heart Normally take up lactate?
True. but produce it Under hypoxia conditions
What are the major sites of regulation of glycolysis and are markedly exergonic and irreversible?
hexokinase, phosphofructokinase, pyruvate kinase
How does fructose enter glycolysis?
- bypasses main regulatory steps
- gets phosphorylated to fructose-1-phosphate
- more PYRUVATE and acetyl coA are formed than is required for ATP formation
In LIVER AND ADIPOSE TISSUE —-> increased lipogenesis
How is PYRUVATE transported into the mitochondrion?
Proton symporter
What enzyme decarboxylates PYRUVATE to hydroxyethyl derivative of thiazole ring of enzyme-bound thiamin diphosphate?
PYRUVATE dehydrogenase
In thiamin deficiency, what happens to glucose metabolism?
Glucose metabolism is impaired and there is significant & potentially life threatening lactic and pyruvic acidosis.
What inhibits PYRUVATE dehydrogenase?
NADH, acetyl CoA
What regulates PYRUVATE dehydrogenase?
phosphorylation (kinase) of 3 serine residues on PYRUVATE dehydrogenase component of multienzyme complex —> decreased activity
Dephosphorylation (phosphatase) —> increased activity
PYRUVATE dehydrogenase — glycolysis is inhibited WHEN
there’s adequate ATP available and when fatty acids are being oxidized
What causes elevated levels of PYRUVATE?
- arsenite and mercuric ions inhibit PYRUVATE dehydrogenase
- thiamin deficiency
What causes hemolytic anemia in erythrocytes?
Inherited aldolase a deficiency
PYRUVATE kinase deficiency
Conditions that involve an impairment of PYRUVATE metabolism frequently lead to….
LACTIC ACIDOSIS
