Glycolysis

[Qurratulain]

glycolysis (glīkŏl'ĭsĭs) , term given to the metabolic pathway utilized by most microorganisms (yeast and bacteria) and by all “higher” animals (including humans) for the degradation of glucose. Glycolysis means, literally, the dissolution of sugar. The process is a series of consecutive chemical conversions that require the participation of eleven different enzymes, most of which have been crystallized and thoroughly studied. Glycolysis begins with a single molecule of glucose and concludes with the production of two molecules of pyruvic acid. The pathway is seen to be degradative, or catabolic, in that the six-carbon glucose is reduced to two molecules of the three-carbon pyruvic acid. Much of the energy that is liberated upon degradation of glucose is conserved by the simultaneous formation of the so-called high-energy molecule adenosine triphosphate (ATP). Two reactions of the glycolytic sequence proceed with the concomitant production of ATP, thus ATP synthesis is said to be coupled to glycolysis. Hundreds of cellular reactions, particularly those involved in the synthesis of cellular components and those that allow the cell to perform mechanical work, require the participation of ATP as a source of chemical energy. While glycolysis is the primary fuel process for some organisms that do not require oxygen, such as yeast, aerobic organisms can only gain a small portion of their needed energy from this process. Glycolysis occurs in two major stages, the first of which is the conversion of the various sugars to a common intermediate, glucose-6-phosphate. The second major phase is the conversion of glucose-6-phosphate to pyruvate. The products of glycolysis are further metabolized to complete the breakdown of glucose. Their ultimate fate varies depending upon the organism. In certain microorganisms lactic acid is the final product produced from pyruvic acid, and the process is referred to as homolactic fermentation. In certain bacteria and in brewer's yeast, lactic acid is not produced in large quantities. Instead pyruvic acid, which is also the precursor of lactic acid, is converted to ethanol and carbon dioxide by an enzyme-catalyzed two-step process, termed alcoholic fermentation. In the tissues of many organisms, including mammals, glycolysis is a prelude to the complex metabolic machinery that ultimately converts pyruvic acid to carbon dioxide and water with the concomitant production of much ATP and the consumption of oxygen.


Source: Columbia University Press

[I M Possible]

Nice job but i think its cyclic diagram is really helpful for practical studies.

Regards

[Qurratulain]

Yara, i tried, but it was going beyond the limits prescribed by the forum. I'll try to edit the diagram (width/ height etc) first and then will post it, so just wait.

[fatima3k]

ASA

@Qurratulaain

Good work.I also have gathered some information about metabolism and Glycolysis.I hope it will be helpful:

Gycolysis


The most pressing need of all cells in the body is for an immediate source of energy. Some cells such as brain cells have severely limited storage capacities for either glucose or ATP, and for this reason, the blood must maintain a fairly constant supply of glucose. Glucose is transported into cells as needed and once inside of the cells, the energy producing series of reactions commences. The three major carbohydrate energy producing reactions are glycolysis, the citric acid cycle, and the electron transport chain.

The overall reaction of glycolysis which occurs in the cytoplasm is
represented simply as:

C6H12O6 + 2 NAD+ + 2 ADP + 2 P -----> 2 pyruvic acid, (CH3(C=O)COOH + 2 ATP + 2 NADH + 2 H+

The major steps of glycolysis are outlined in the graphic on the left. There are a variety of starting points for glycolysis; although, the most usual ones start with glucose or glycogen to produce glucose-6-phosphate. The starting points for other monosaccharides, galactose and fructose, are also shown.


Facts about Glycolysis:
The major steps of glycolysis are outlined in the graphic on the left. There are a variety of starting points for glycolysis; although, the most usual ones start with glucose or glycogen to produce glucose-6-phosphate. The starting points for other monosaccharides, galactose and fructose, are also shown.

Glycolysis - with white background for printing

There are five major important facts about glycolysis which are illustrated in the graphic.

1) Glucose Produces Two Pyruvic Acid Molecules:

Glucose with 6 carbons is split into two molecules of 3 carbons each at Step 4. As a result, Steps 5 through 10 are carried out twice per glucose molecule. Two pyruvic acid molecules are the end product of glycolysis per mono- saccharide molecule.

2) ATP Is Initially Required:

ATP is required at Steps 1 and 3. The hydrolysis of ATP to ADP is coupled with these reactions to transfer phosphate to the molecules at Steps 1 and 3. These reactions evidently require energy as well. You may consider that this is a little strange if the overall objective of glycolysis is to produce energy. This energy is used in the same way that it initially takes heat to ignite the burning of paper or other fuels - you need to expand some energy to get it started.

3) ATP is Produced:

Reactions 6 and 9 are coupled with the formation of ATP. To be exact, 2 ATP are produced at step 6 (remember that the reaction occurs twice) and 2 more ATP are produced at Step 9. The net production of "visible" ATP is: 4 ATP.

Steps 1 and 3 = - 2ATP
Steps 6 and 9 = + 4 ATP
Net "visible" ATP produced = 2.
Important Facts about Glycolysis (cont.):

4) Fate of NADH + H+:

Reaction 5 is an oxidation where NAD+ removes 2 hydrogens and 2 electrons to produce NADH and H+. Since this reaction occurs twice, 2 NAD+ coenzymes are used.

If the cell is operating under aerobic conditions (presence of oxygen), then NADH must be reoxidized to NAD+ by the electron transport chain. This presents a problem since glycolysis occurs in the cytoplasm while the respiratory chain is in the mitochondria which has membrane that is not permeable to NADH. This problem is solved by using glycerol phosphate as a "shuttle." - see graphic on the left. The hydrogens and electrons are transferred from NADH to glycerol phosphate which can diffuse through the membrane into the mitochondria. Inside the mitochondria, glycerol phosphate reacts with FAD coenzyme in enzyme complex 2 in the electron transport chain to make dihydroxyacetone phosphate which in turn diffuses back to the cytoplasm to complete the cycle.

As a result of the the indirect connection to the electron transport at FAD, only 2 ATP are made per NAD used in step 5. If step 5 is used twice per glucose, then a total of 4 ATP are made in this manner.

If the cell is anaerobic (absence of oxygen), the NADH product of reaction 5 is used as a reducing agent to reduce pyruvic acid to lactic acid at step 10. This results in the regeneration of NAD+ which returns for use in reaction 5.

[fatima3k]

metabolism Diagram

[fatima3k]

glycolysis Diagram

[Muhammad T S Awan]

MashALLAh!

great work dear sis Qurat and Fatima....

but my dear fellows, these diagrams are of much professional type to be required for relevant optional papers like Botany or Zoology.

As regards paper of Every Day Science, one just need a simple diagram, lets say, Glucose (arrow) Glucose 6 Phosphat (arrow) Fructose 6 Phosphat (arrow) Fructose 1, 6 diphosphate.... and so on

sorry jee, i m unable to put arrows in the box