fermentation and regulation of glycolysis

Fate of Pyruvate

made into ethanol or lactate if no oxygen. Made into acetyl CoA if there is oxygen

Fermentation

In presence of no oxygen but not preferred bc it doesn’t yield as much ATP. Also restores NAD+

Which form of fermentation do humans do

Lactate fermentation

Oxidative phosphorylation

Needs oxygen. Pyruvate to Acetyl CoA and further oxidation

Pyruvate to ethanol- alcohol fermentation

Pyruvate into acetylaldehyde by Pyruvate decarboxylase and then into ethanol by alcohol dehydrogenase.

Why does NAD+ need to be restored

NAD+ made by alcohol dehydrogenase or lactate dehydrogenase fuels the formation of 1,3-BPG. That forms NADH which helps form ethanol or lactate

Pyruvate to lactate- lactic acid fermentation

Pyruvate into lactate by lactate dehydrogenase

What are the regulation points in glycolysis

The irreversible enzymatic rxns.

Regulation of glycolysis at rest- PRK

ATP allostericlly inhibit PFK at a different site from catalytic site (high energy charge) AMP competes for spot but doesn’t inhibit.

Why is there no ADP in regulation of glycolysis

Bc it could easily be turned into ATP

What is the most importanr regulatory point

Phosphofructokinase

Regulation of glycolysis- Hexokinase

A high concentration of G6P creates -ve feedback on Hexokinase

Regulation of glycolysis - private kinase

Allosteric inhibition by ATP or activation by fructose 1,6-bus phosphate

Regulation of glycolysis in liver

Glucose stored as glycogen when too much glucose. Release stored glucose if blood sugar level is low. Use glucose for biosynthesis

Regulation of PFK in liver

After Pyruvate and ATP are made, Pyruvate makes citrate. ATP and citrate have negative inhibition on PFK

Feedforward stimulation of PFK in liver

Fructose 6-phosphate makes fructose 2,6-bisphosphate which activates PFK

Regulation of Hexokinase in liver

Instead of Hexokinase liver has glucokinase which is an isozyme of Hexokinase. Glucokinase activated when there is a high concentration of sugar in blood

What happens to glucokinase when blood glucose is high

Insulin is activated in response to high glucose levels and activates glucokinase

What happens to glucokinase when blood glucose is low

GKRP is activated in response to low glucose levels and inhibits glucokinase

is in all metabolizing cells, acts on expose sugars, low Km/higher affinity, low Vmax/saturation at lower level, G6P regulates

Hexokinase

In liver and pancreatic cells, acts only on glucose, high Km/lower affinity to glucose, high Vmax/high capacity towards glucose, insulin stimulates

Glucokinase

Pyruvate kinase regulation in liver

Fructose 1,6-bisphosphate stimulates Pyruvate kinase. Pyruvate makes alanine. Alanine and ATP inhibit Pyruvate kinase

Reversible phosphorylation

Inactive form of Pyruvate kinase is phosphorylated (glucagon) becomes active form without phosphate and can go back and forth