You are currently browsing the tag archive for the ‘enolase’ tag.

Hey you masses of scientists!  Today, since I feel rather prepared for my biochemistry exam tomorrow, I felt like reviewing what I learned with you all.  This post (and the *hopefully* two subsequent) will overview the topics of my exam and help both myself and you!  Ah, what a symbiotic relationship we have!  Anyways, lets get down to buisness.

Glycolysis–The cycle in overview!

In Overview.

Ahhh, sugar. <3Step 1: Phosphate (-OPO3-2 in our case) is added onto the sixth carbon of glucose to form Glucose-6-Phosphate.  This reaction occurs via the O- (formerly OH) group of C6’s nucleophilic attack on ATP’s third phosphoryll group.  Hexokinase aids the reaction (via a Lys group) and thusly ADP and H+ (from the -OH group) are formed as products.

**Gluconeogenesis–glucose-6-phosphatase catalyzes the reverse reaction, since this step is IRREVERSIBLE**

Step 2: Glucose-6-Phosphate is then isomerized to fructose-6-phosphate.  Via two His groups from phosphoglucose isomerase, the 6 membered ring of G6P is opened up and then reclosed as a 5 membered fructose ring; the phosphate group remains unchanged.  This reaction is reversible (and works backwards for gluconeogenesis).

Step 3: Fructose-6-phosphate picks up another phosphate group via the same mechanism as step 1.  The C1 carbon of F6P then picks up a phosphate group via nucleophilic attack on ATP.  Phosphofructokinase catalyzes the reaction to form Fructose 1,6 bisphosphate.  ADP and H+ are released as side products.

**Gluconeogenesis–The reverse is catalyzed by fructose bisphosphate since this reaction is IRREVERSIBLE!**

Note the action center in the center of the enzyme.Step 4: Fructose 1,6 bisphosphate is then cleaved at the third carbon to produce D-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. Fructose bisphosphate aldolase catalyzes the reaction.  It leaves two, three carbon chains–one aldehyde and one keytone.  The reaction is reversible.

Step 5: The keytone (C1) in Dihydroxyacetone phosphate is reduced to an alcohol, while the alcohol (C2) is oxidized into a keytone, thusly making a second glyceraldehyde-3-phosphate.  Triosephosphate isomerase catalyzes the reaction and it is reversible.

Step 6: (From here on out, there are two equivalents of each molecule *i.e. G3P). The two glyceraldehyde-3-phosphates then pick up a second phosphate group (from Pi, not ATP) onto C3.  The aldehyde (=O) is moved to C1 and the OH on C2 becomes out instead of in (to the page).  This forms 1,3-bisphosphoglycerate and is catalyzed by glyceraldehyde phosphate dehydrogenase (GAPDH).  NAD+ is reduced to NADH and H+.  This reaction is reversible.

Step 7: 1,3 Bisphosphoglycerate then has its C1 phosphate group removed leaving just the oxygen (O-).  3-phosphoglycerate is formed as is ATP via the catalyst phosphoglycerate kinase.  This reaction is reversible.

Step 8: 3-phosphoglycerate then has its C3 phosphate group moved to C2, forming 2-phosphoglycerate.  Phosphoglycerate mutase is the catalyst and the reaction is reversible.

Step 9: 2-phosphoglycerate is then dehydrogenated at the C3 carbon to form a double bond between C3 and C2, forming phosphoenolpyruvate. The OH group on C3 is removed and pulls a proton off of C2 in the process, forming the double bond.  Enolase catalyzes the reaction, which is reversible.  Water is formed.

Pyruvate with its Na ion, balancing the negative charge on O.Step 10: Phosphoenolpyruvate then has its phosphate group (C2) removed to form ATP via pyruvate kinase. This leaves a keytone group on C2 while fully hydrogenating C3 (methyl group) called Pyruvate. ADP and H+ are consumed, while ATP is produced.

**Gluconeogenesis–this step is catalyzed via two enzymes, pyruvate carboxylase and phosphoenolpyruvase.  Pyruvate carboxylase turns pyruvate to oxaloacetate which is then transformed into phosphoenolpyruvate by phosphoenolpyruvase.  This reaction, obviously, is IRREVERSIBLE!**

The net gain of glycolysis is 2 ATP (4ATP were formed but 2 were consumed initially) and 2 NADH.

That’s glycolysis in a nutshell.  Hopefully, the step wise explanation of the reactions (minus mechanisms, sorry!) will aid you all in your studies of biochemistry.  NOW! On to the Citric Acid Cycle!

Cheers,

The Alchemist Kitten

Advertisements

Currently, Kitten…

Error: Twitter did not respond. Please wait a few minutes and refresh this page.

Past Experiments