GLYCOLYSIS BEGINS

Okay, what am I doing here in this biology power-point presentation? Since the presentation is about glycolysis, it looks like someone mixed it up with Gieco and thought they heard Geicolysis. By the way, I’m a Gecko not a Giecko. It’s an interesting word, lysis, used here as a suffix. Lysis means split and glyco means sugar, so glycolysis means splitting of sugar.

Now don’t get me wrong, but I really am no biochemistry expert. They just hire me for a job and I do whatever earns me a paycheque. So even though I know I have been misplaced I’ll simply read the teleprompter. After all, if the American president can get away with it, why can’t I? In the process of Glycolysis, glucose, a six carbon sugar, is split into two three carbon sugars. These smaller sugars generate ATP, NADH and water, turning it into pyruvate (pyruvic acid). The ATP generated, is formed by substrate level phosphorylation. Almost all cells utilize the glycolysis pathway. It is common to bacteria, protozoa, fungi, plants and animals like you and me. It is the first pathway in the breakdown of glucose to form energy for cells. It is used by both aerobic (with O 2 ) and anerobic pathways Remember substrate level phosphorylation

First it’s important to familiarize yourself with the chemicals in the pathway. Here is a listing of those chemicals sequenced for glycolysis. GLUCOSE GLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACETONE PHOSPHATEGLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE Notice that dihydroxyacetone phosphate is converted into G-3-P. Thus this bottom sequence progresses twice to make two pyruvates. The numbering of carbons is important in order to identify the positions of the phosphates on the carbon chains. Ex. Glucose-6- phosphate has a phosphate on the last (sixth) carbon in the six carbon chain of glucose. There are ten steps in the glycolytic process. Now you must remember the sequence

GLUCOSE GLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACETONE PHOSPHATE GLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE Now it’s time for you to sequence glycolysis

GLUCOSE Starts the process. It is a six carbon sugar. Remember how to number the carbons because it will be important in order to identify the positions of the phosphates later in subsequent molecules. In the cell rising ADP levels stimulate glycolysis.

GLUCOSE-6-PHOSPHATE C-C-C-C-C-C FRUCTOSE-6-PHOSPHATE This is just an isomer of the glucose and the phosphate position is not altered. An ATP molecule has been used to donate its phosphate to glucose carbon 6. P This is what glucose-6- phosphate actually looks like Glucose -6- phosphate skeleton simplified ATP Used

FRUCTOSE-1,6-DIPHOSPHATE P C-C-C-C-C-C P Another ATP has been used up and has donated its phosphate to fructose carbon 1 This molecule is cleaved –cut down the center- to form two three carbon sugars with one phosphate each. These new three carbon sugars are dihydroxyacetone phosphate and glyceraldehyde-3-phosphate G-3-P. Cut here (cleavage) Cleaveage cut on complete sugar Fructose-1.6- Diphosphate skeleton simplified ATP Used

DIHYDROXYACETONE PHOSPHATE Can you remember the chemical group this belongs to from my lesson? It’s a ketone!! Dihydroxyacetone phosphate and G-3-P are created in equal amounts and would remain equal at equilibrium, but the cell constantly uses up the G-3-P and not the dihydroxyacetone phosphate, thus pulling the equilibrium to produce more G-3-P DIHYDROXYACETONE PHOSPHATE GLYCERANDEHYDE-3- PHOSPHATE ENZYME ISOMERASE

GLYCERALDEHYDE-3-PHOSPHATE Can you identify the aldehyde group in this molecule. I hope you can because I expect you to remember it from my lesson! Aldehyde group P -C-C-C G-3-P simplified skeleton

1,3-DIPHOSPHOGLYCERATE P P -C-C-C Oxidation of G-3-P by NAD+ releases a lot of energy and it is enough to power the creation of NADH and also the attachment of an inorganic phosphate onto the carbon chain. There is now a phosphate on carbon 1. Where did it come from? NADH Formed PHOSPHATE inorganic added

3-PHOSPHOGLYCERATE P -C-C-C ATP Formed What happened to the phosphate on carbon 1? This high energy phosphate bond is transferred to ADP to make an ATP molecule

2-PHOSPHOGLYCERATE P -C-C-C No worries here. This is just an isomeric change.

PHOSPHOENOLPYRUVATE P -C-C-C As water is removed from 2phosphoglycerate to form phosphoenolpyruvate the phosphate takes on a high energy characterictistic and will be used to make ATP. H 2 O removed

PYRUVATE -C-C-C ATP Formed This is the last chemical in the glycolysis sequence. All the phosphates have been removed to make ATP molecules.

.GLUCOSE GLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACETONE PHOSPHATE GLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE Now its time to add the details to the pathway ATP used ATP used Pi added NADH formed ATP formed H 2 O formed

. GLUCOSEGLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACETONE PHOSPHATE GLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE It’s your turn to put the entire pathway together now! ATP used ATP used Pi added NADH formed ATP formed H 2 O formed 22222

.GLUCOSE GLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACETONE PHOSPHATE GLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE ATP used ATP used Pi added NADH formed ATP formed H 2 O formed It’s very important to remember that for each glucose that enters the pathway, two pyruvate are created. All products are also 2X In order to get gylcolysis initiated, 2 ATP must be used and converted into the lower energy ADP + P i. 4 ATP are generated in these steps but this is a gross gain. If you count the two that had to be used up you get only 2 net ATP from glycolysis Now for some facts about the overall process

Now as we approach the end of this presentation, I want to make it clear that you are expected to be able to sequence all these terms as shown in the previous slide. You do not, however, need to have the names of the chemicals memorized. Yet, you should become familiar with them as they will be used in our further study into metabolism and photosynthesis.

GLUCOSE GLUCOSE-6-PHOSPHATE FRUCTOSE-6-PHOSPHATE FRUCTOSE-1,6-DIPHOSPHATE DIHYDROXYACE TONE PHOSPHATE GLYCERALDEHYDE-3-PHOSPHATE(G-3-P) 1,3-DIPHOSPHOGLYCERATE 3-PHOSPHOGLYCERATE 2-PHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE PYRUVATE Now I’ll show you the enzymes involved in each step. Hexokinase Phosphoglucoisomerase Phosphofructokinase Aldolase Isomerase Triose phosphate dehydrogenatse Phosphoglycerokinase Phosphoglyceromutase Enolase Pyruvate kinase Worried yet? It’s okay, you do not have to memorize or sequence these enzymes. You just need to know there are there and get some familiarity with them.

So there you go, that is the process of glycolysis. Just a little word of advice. Next time you need to learn important biochemical pathways, use an expert and not a gecko. I wonder if that applies to insurance as well? Anyway, have a good day.

End Glycolysis