AC Lecture 61: Glycolysis: Functions, pathways, energetics, regulations Flashcards
What is the basic overall reaction of glycolysis?
Glucose + 2 NAD+ + 2Pi + ADP –> 2 pyruvic acid + 2ATP + 2NADH
What is the first step of Glycolysis?
Glucose + ATP –> Glucose-6-P + ADP +Pi via hexokinase
What organ systems use glycolysis for energy exclusively?
RBCs and brain
embryonic tissue, retina, adrenals, some immune cells, exercising muscles (major source)
Which steps in glycolysis are irreversible?
1, 3, and 10
What is the second step of glycolysis?
G6P –> Fructose 6-P
via phosphoglucoisomerase
What is the third step of glycolysis?
F6P + ATP –> F1,6bisP + ADP
via PF1K RATE LIMITING
What regulates the rate limiting step of glycolysis (not in the liver)?
the third step of glycolysis is catalyzed by PFK which is…
inhibited by ATP and citrate
stimulated byAMP, Pi, NH4, F1,6bisP
What kinds of sites does PFK have?
two substrate binding sites (ATP, F6P)
two allosteric inhibitory sites
four allosteric activator sites
What regulates the rate limiting step of glycolysis (in the liver)?
the third step of glycolysis is catalyzed by PFK which is…
insulin stimulated
glucagon inhibited
What is the fourth step of glycolysis?
F1,6bisP –> DHAP + G3P
via aldolase
What is the sixth step of glycolysis?
G3P + NAD+ + Pi –> 1,3bis phosphoglyceric acid + NADH
via gluceraldehyde 3-P dehydrogenase
Note: oxygen independent
What is the function of 1,3 bis PGA?
it is a high energy compound that traps energy that would have been released as heat
What is the seventh step of glycolysis?
1,3 bis PGA + ADP –> 3 PGA + ATP
via phosphoglycerate kinase
What is substrate level phosphorylation?
the transfer of energy to a high energy intermediate which can produce ATP
Which enzyme in glycolysis is highly sensitive to poisoning by heavy metals?
phosphogycerate kinase (enzyme of glycolysis 7) Hg, Cd, Pb
What effect does arsenic have on the body?
competes with Pi for G3P in the G3PDH reaction to form arseno-3-phosphoglyceric acid rather than 1,3 bisP that releases energy as heat rather than as ATP
glycolysis continues, but no ATP is produced- this is a problem for RBCs who use this as their only source for ATP –> anemia
What is the eighth step of glycolysis?
3 phosphoglycerate –> 2-phosphoglycerate
via phosphoglyceromutase
What is the ninth step of glycolysis?
2PGA –> Phosphoenolpyruvate (PEP) + H2O
via enolase
What is an inhibitor of enolase?
fluoride
What is the tenth step of glycolysis?
PEP + ADP –> Pyruvate + ATP
via pyruvate kinase
Which steps of glycolysis participate in substrate level phosphorylation?
seven and ten
How is pyruvate kinase regulated?
inhibited by ATP, NADH, and acetyl CoA stimulated by F1,6 bis P inhibited by glucagon (epi) cAMP-PKA phosphorylation stimulated by insulin
What is the net ATP yield for one mol of glucose through glycolysis?
net 2 ATP
2 ATP consumed, 4 ATP produced
Describe the process of fructose metabolism in the liver.
- Fructose + ATP –> Fructose 1P
via fructokinase - Fructose 1P –> Glyceraldehyde + Dihydroxyacetone P
via aldose - Glyceraldehyde + ATP –> Glyceraldehyde 3P + ADP
via triose kinase - G3P –>–> Pyruvate
