Glycolysis Flashcards

Comprehensive vocabulary flashcards covering the enzymatic steps, regulatory mechanisms, and clinical correlations of the glycolysis pathway.

Hexokinase I

The tissue-specific form of hexokinase localized in the brain and red blood cells.

Hexokinase II

The tissue-specific form of hexokinase localized in the muscle.

Hexokinase IV

The tissue-specific form of hexokinase localized in the liver and pancreas.

Embden-Meyerhof-Parnas (E.M.P.) pathway

An alternative name for the glycolysis pathway which occurs in the cytoplasm.

Preparatory phase

The first phase of glycolysis involving the phosphorylation of glucose and its conversion to glyceraldehyde 3-phosphate, requiring the investment of two $ATP$ molecules.

Payoff phase

The oxidative conversion of glyceraldehyde 3-phosphate to pyruvate, yielding a net gain of $2 NADH$ and $2 ATP$.

Glycolysis End Products

The net result of converting one glucose molecule: $2 \text{ Pyruvate}$, $2 \text{ ATP}$, and $2 \text{ NADH}$.

Hexokinase

The enzyme in step 1 that uses cofactor $Mg^{2+}$ to phosphorylate glucose, undergoing an 'induced fit' shape change upon binding.

Phosphohexose Isomerase

Also known as phosphoglucose isomerase, it catalyzes the rearrangement of carbonyl and hydroxyl groups at $C-1$ and $C-2$ to convert glucose 6-phosphate to fructose 6-phosphate.

Phosphofructokinase-1 (PFK-1)

A regulatory enzyme that catalyzes the first 'committed' step in glycolysis by phosphorylating fructose 6-phosphate to fructose 1,6-bisphosphate.

PFK-1 Allosteric Regulation

Regulated positively by $AMP$ and fructose 2,6-bisphosphate, and negatively by $ATP$ and citrate.

Fructose 1,6-bisphosphate Aldolase

An enzyme that performs a reversible aldol condensation to cleave fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.

Triose Phosphate Isomerase

The enzyme responsible for the interconversion of dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

Glyceraldehyde 3-phosphate dehydrogenase

An enzyme that uses $NAD^{+}$ (Vitamin B3) to oxidize the aldehyde group of G-3-P and add inorganic phosphate to form 1,3-bisphosphoglycerate.

Substrate-level phosphorylation

The process where $ADP$ is converted to $ATP$ by the direct transfer of a phosphoryl group from a high-energy compound.

Phosphoglycerate mutase

An enzyme that catalyzes the reversible shift of a phosphoryl group between $C-2$ and $C-3$ using $Mg^{2+}$ as an essential cofactor.

Enolase

A lyase enzyme that removes a molecule of $H_{2}O$ from 2-phosphoglycerate to yield phosphoenolpyruvate.

Pyruvate kinase

The enzyme for the second substrate-level phosphorylation step, requiring $K^{+}$ and $Mg^{2+}/Mn^{2+}$, which serves as a secondary regulation point.

Lactate Dehydrogenase

The enzyme involved in anaerobic glycolysis that forms lactic acid, which then diffuses out of the cell into the bloodstream for metabolism in the liver or heart.

Ethanol Formation

An anaerobic process in yeast involving pyruvate decarboxylase and alcohol dehydrogenase ($ADH$) to detoxify acetaldehyde into ethanol.

Auto-brewery syndrome

A condition where the fungi $S. \text{ cerevisiae}$ overgrows in the gut microbiome, leading to systemic alcohol intoxication via the conversion of pyruvic acid to ethanol.

Thiamine pyrophosphate (TPP)

The active form of Vitamin B1 which serves as a co-enzyme for several enzymes in carbohydrate metabolism, such as pyruvate decarboxylase.

Hypoxemia

A severe reduction in the amount of oxygen delivered to tissues for cellular respiration, which can lead to metabolic acidosis due to elevated plasma lactic acid.