Intro and Overview
00:00:00Glycolysis is the process of oxidizing glucose, a six-carbon molecule, into pyruvate. Glucose is obtained from our diet and brought into cells for oxidation through various steps. However, glucose cannot passively move through the cell membrane by diffusion due to its water-soluble nature.
Glucose (Glut) Transporters
00:01:29Glut transporters are specialized transporters that bring glucose into the cell. They can move glucose bidirectionally, from inside to outside the cell. There are different types of glut receptors categorized as Glut1, Glut2, and Glut3. Glut1 is found in red blood cells and at the blood-brain barrier. Glut2 is present in the kidney, liver, pancreas, and gastrointestinal tract. And finally, glint3 is found in placenta neurons.
Glucose-6-Phosphate
00:06:30Glucose is transported into the cell through glut transporters. To prevent glucose from moving back out, a phosphate group is added to the six carbon of glucose, forming glucose-6-phosphate. This process involves enzymes called hexokinase or glucokinase.
Fructose-6-Phosphate
00:10:20The enzyme phospho hexose isomerase catalyzes the conversion of glucose 6-phosphate into fructose 6-phosphate. This step is irreversible and crucial in the metabolic pathway.
Fructose-1,6-biphosphate
00:11:40The enzyme phosphofructokinase type one (PFK-1) is involved in the irreversible step of converting fructose-1,6-biphosphate. PFK-1 adds a phosphate group to the six carbon of fructose, resulting in fructose 1,6 bisphosphate. This process requires ATP and converts it into ADP.
Dihydroxy Acetone Phosphate / Glyceraldehyde-3-Phosphate
00:14:00Dihydroxy Acetone Phosphate "Dihydroxyacetone phosphate" is a three-carbon molecule with a ketone in the middle and a phosphate on one of the carbons. It needs to be converted into another molecule called "glyceraldehyde-3-phosphate" before it can be utilized in glycolysis pathway.
"Glyceraldehyde-3-Phosphate" "Glyceraldehyde-3-phosphate" is different from dihydroxyacetone phosphate as it has an aldehyde group on one end. The enzyme involved in splitting dihydroxyacetone phosphate and converting it into glyceraldehyde-3-phosphate is called aldolase.
Triose Phosphates Interconversion To convert dihydroxyacetone phosphate into glyceraldehye - 3 -phospate, an enzyme called triose phosphatase isomerase facilitates their interconversion.
1,3-biphosphoglycerate
00:17:24"1,3-biphosphoglycerate" is formed by adding another phosphate to the molecule. This step involves an enzyme called glyceraldehyde 3-phosphate dehydrogenase (GAPDH), which adds NAD+ and removes hydrides from glycerol-3-phosphate. The resulting molecule is converted into NADH.
3-phosphoglycerate
00:20:30In this step, a phosphate is lost from the substrate, resulting in the formation of 3-phosphoglycerate. The enzyme phosphoglycerate kinase plays a key role by converting DP to ATP, producing two ATP molecules.
2-phosphoglycerate
00:22:30- The conversion of 3-phosphoglycerate to 2-phosphoglycerate is a simple reaction. - By switching the position of the phosphate group from the third carbon to the second carbon, we obtain 2-phosphoglycerate. - This reaction is catalyzed by an enzyme called phosphoglycera
Phosphoenol-pyruvate (PEP)
00:23:40Phosphoenol-pyruvate (PEP) undergoes a structural modification called an enol conversion. The phosphate group is transferred to create phospho enol, resulting in the formation of phosphoenolpyruvate. This modification is facilitated by the enzyme enolase.
Pyruvate Kinase
00:25:25In glycolysis, the enzyme pyruvate kinase plays a crucial role in converting phosphoenolpyruvate into pyruvate. This step is highly regulated and irreversible. Pyruvate kinase transfers the phosphate from phosphoenolpyruvate onto ADP to produce ATP. The overall process results in the production of two molecules of ATP.
Anaerobic
00:27:10During anaerobic conditions, pyruvate can be converted into lactic acid by the enzyme lactate dehydrogenase. This occurs when there is no oxygen or very little oxygen available. The NADH molecules unload their hydrides onto pyruvate since they cannot deliver them to the electron transport chain without oxygen. Lactic acid can then be further metabolized in the liver to produce glucose or ATP, depending on the body's needs.
Wrap Up
00:30:55Glycolysis occurs in the cytoplasm of the cell. The starting substrate is glucose, and the end product is two pyruvates. In this process, a total of four ATP molecules are produced, but only two net ATP molecules are generated due to using two ATP at the beginning step. Two NADH molecules are also generated. Glycolysis is an anaerobic process that can produce lactic acid when there's low or no oxygen.