Flashcards in Mitsoura - Glycolysis Deck (31):
Describe the sources of GLUCOSE for glycolysis and how these sources are used as a function of metabolic state
Dietary intake (fed state), from glycogenolysis (fasting state), from gluconeogenesis (starving state - new glucose synthhesis)
Where is glucokinase found/located?
liver and pancreas only
Glucokinase has a high Km for glucose. What does this mean?
It has a low affinity for glucose and therefore it has a high Vmax
When does glucokinase work best?
Works best during the fed state to take in large amounts of blood glucose
What sugars does glucokinase have an affinity for?
Where is hexokinase found/located?
all tissues and organs outside liver and pancreas
When does hexokinase work best?
it works at all metabolic states
What effect does insulin have on glucokinase and hexokinase?
insulin has no effect on hexokinase, but glucokinase is inducible by it
What sugars does hexokinase have an affinity for?
Glucose, Galactose, and Fructose
What is the investment phase of glycolysis?
Step #1: Glucose → Glucose-6-Phosphate (enzyme: hexokinase/glucokinase)
Step #3: Fructose-6-Phosphate → Fructose-1,6-bisphosphate (enzyme: PFK-1)
What is the splitting phase?
Step #4: Fructose-1,6-bisphosphate → Glyceraldehyde-3-Phosphate (G3P) + Dihydroxyacetone Phosphate (DHAP)
(enzyme: Aldolase A)
How many energy generating steps are there?
there are 3 steps
List the first energy generating step
Step #: G3P ↔ 1,3-biphosphoglycerate
(enzyme: glyceraldehyde phosphate dehydrogenase)
generates 2 NADH
Where do the NADHs from the first energy generating step go?
to electron transport chain for ATP production
List the second energy generating step
1,3-biphosphoglycerate ↔ 3-Phosphoglycerate
(enzyme: phosphoglycerate kinase)
generates 2 ATP
List the third energy generating step
Phosphoenolpyruvate (PEP) → Pyruvate
(enzyme: pyruvate kinase)
generates 2 ATP
[this is a regulated step]
What is the net energy generated in glycolysis
2 ATP and 2 NADH
How much energy is produced anaerobically?
2 ATP, zero NADH
How does insulin stimulate glycolysis?
by activating PFK-2, catalyzing F-6-P → F-2,6-bisphosphate, which acts as an allosteric activator of PFK-1
How does glucagon inhibit glycolysis?
by activating F-2,6-bisphosphatase, catalyzing F-2,6-bisP → F-6-P, which then inhibits PFK-1
What stimulates and inhibits glucokinase?
stimulation: insulin and glucose
inhibition: glucagon and ATP
What inhibits hexokinase?
ATP and glucose-6-phosphate (G-6-P)
What stimulates and inhibits phosphofructokinase-1 (PFK-1)?
stimulation: AMP, Insulin, Fructose-2,6-bisphosphate
inhibition: Glucagon, ATP, Citrate (TCA cycle)
What stimulates and inhibits pyruvate kinase?
stimulation: Insulin, Fructose-1,6-bisphosphate
inhibition: ATP and Glucagon
When does lactic acidosis occur?
it occurs when there is a build up of lactate
What is the build up of lactate due to?
high concentrations of Pyruvate
What enzyme converts Pyruvate to Lactate?
What diseases cause/result in lactic acidosis?
severe lung disease, Von Gierke's (GSD), Leukemia, Metastatic carcinoma
What two deficiencies cause/result in lactic acidosis?
Pyruvate dehydrogenase deficiency and α-ketoglutarate dehydrogenase deficiency
What 6 other conditions/factors result in lactic acidosis?
strenuous exercise, high altitude, drowning, carbon monoxide poisoning, cyanide poisoning, and alcohol intoxication