glycolysisreview

8/8/2019 glycolysisreview

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Mr. Earl Benjamin III

MS in Chemistry, Morgan State University

Presentation on 3/18/04

Review of Glycolysis

1. What is Glycolysis?

Glycolysis is the sequence of reactions that converts glucose into pyruvate with

the concomitant production of a relatively small amount of ATP. Glycolysis can

be carried out anerobically (in the absence of oxygen) and is thus an especially

important pathway for organisms that can ferment sugars. For example, glycolysis

is the pathway utilized by yeast to produce the alcohol found in beer. Glycolysis

also serves as a source of raw materials for the synthesis of other compounds. For

example, 3 phosphoglycerate can be converted into serine, while pyruvate can be

aerobically degraded by the Krebs or TCA cycle to produce much larger amounts

of ATP.

2. Why do animal need glycolysis?

Glycolysis is perhaps the first step in the of all energy producing.

3. Where does glycolysis occur?

Glycolysis occurs in most area of the cell.

4. What is/are the reactants/reagents necessary for glycolysis?

Glycolysis of requires glucose to produce energy.

5. What is/are the product of glycolysis?

Glycolysis produces a net amount of 2 ATP and 2NADH

4. Does this process need or use oxygen?

No it does not need large amounts of energy.

5. How much energy does glycolysis produce?

Glycosis produces 2ATP and 2 NADH which then goes into the Oxidative

Phosphorylation cycle which then produces more ATP.

6. What is the advantage of producing energy from glycolysis?


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Glycolysis, is considered as the basis for all energy processes in the cell.

Althoug it only produces low levels of ATP, normally called basal levels, this

process also produces large quantities of NADH which when processed by the

Oxidative Phosphorylation pathway can produce large amount of energy.

Glycolysis can also be carried out throughout the cell, which gives it an advantage

over the TCA and Oxidative phosphorylation cycles that occur in the

mitochondria.


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Review of Pyruvate Dehydrogenase (PDH) Complex

The fate of pyruvate depends on the cell energy charge. In cells or tissues with a high

energy charge pyruvate is directed toward fatty acid synthesis, but when the energy


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charge is low pyruvate is preferentially oxidized to CO2 and H2O in the TCA cycle, with

generation of 15 equivalents of ATP per pyruvate.

What is the Pyruvate Dehydrogenase (PDH) Complex ?

The PDH Complex is a series of biological step that prepare the pyruvate

produced in glycolysis to go into the TCA cycle. These processes chemically

convert pyurvate to Acetyl-CoA that can then enter the TCA cycle.

What are the reactants for the PDH cycle?

Pyruvate from glycolysis

What is the product of the PDH cycle?

Acetyl-CoA

What is the advantage of using this process?

This process allow for the chemical conversion of pyruvate into Acetyl-Co A

which can then be inserted into the TCA cycle for processing.


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Review of Citrus Acid Cycle

1.What is the Citrus Acid Cycle?Krebs cycle or the citric acid cycle or tricarboxylic acid cycle is the common

pathway to completely oxidize fuel molecules that mostly is acetyl CoA, the

product from the oxidative decarboxylation of pyruvate. It enters the cycle and

passes ten steps of reactions that yield energy and CO2.

Where does the Citrus Acid Cycle occur?

The mitochondrial membrane

Does the TCA Cycle need or use oxygen?

Yes. The Citrus Acid Cycle does need oxygen.

How much energy does the TCA cycle produce?

Per turn of the TCA cycle 3 NADH, 1 FADH2, and 1ATP

What is the reactant of the TCA cycle?

Acetyl-CoA produced from the pyruvate from glycolysis and converted by the

PDH complex. Citrate is also a reactant, which can come from OAA in the citrus

acid cycle.

What is the product of the TCA cycle?

In fact since the TCA cycle feed backs into itself there is no net products.

However, TCA cycle 3 NADH, 1 FADH2, and 1ATP are produced each turn.

What is the advantage of the TCA cycle?

The advantage of the TCA cycle is that it cycles that it can cycle which means

that it can repeat for several times to accumulate several products which can be either

used as direct energy or put into the oxidative phosphorylation pathway which can

produce large amounts of energy.


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Citrus Acid Cycle Steps

Step 1:

Reaction: Acetyl CoA+Oxaloacetate to CitrateEnzyme: Citrate synthaseReaction type: CondensationDescription: Acetyl CoA condenses with oxaloacetate first,to form citrylCoA. Then citryl CoA is hydrolyzed to citrate and CoA

Step 2.

Reaction: Citrate to cis-AconitateEnzyme: Aconitase

Reaction Type: Dehydration

Description: Citrate is isomerized to isocitrate by this first

dehydration and yields cis-aconitate as an

intermediate.


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Step 3.

Reaction: cis-Aconitate to IsocitrateEnzyme: AconitaseReaction Type: Hydration

Description: Hydration of cis-aconitate gives the interchange of H

atom and OH group from the step 2.

Step 4.

Reaction: Isocitrate to alpha-KetoglutarateEnzyme: Isocitrate dehydrogenase

Reaction Type: Oxidative decarboxylation

Description: Dehydrogenation of isocitrate occurs and yields

oxalosuccinate as an intermediate.Then CO2 leaves to

have alpha-ketoglutarate.This reaction gives NADH.

Step 5.Reaction: alpha-Ketoglutarate to Succinyl CoAEnzyme: alpha-Ketoglutarate dehydrogenase complex

Reaction Type: Oxidative decarboxylation

Description: This mechanism is almost as same as the reaction of

the oxidative decarboxylation of pyruvate to acetyl

CoA by pyruvate dehydrogenase complex. This

reaction gives one NADH.

Step 6.

Reaction: Succinyl CoA to SuccinateEnzyme: Succinyl CoA synthetaseReaction Type: Substrate-level phosphorylation

Description: The thioester bond of succinyl and CoA is an energy rich

bond. Thus only this step gives a high-energy phosphatecompound,GTP from the couple reactions of the thioester

bond cleavage and the phosphorylation of GDP.

Step 7.

Reaction: Succinyl CoA to SuccinateEnzyme: Succinate dehydrogenase

Reaction Type: OxidationDescription: The two hydrogens of succinate leave to an acceptor,

FAD. Then this reaction yields fumarate and FADH2.


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Step 8.

Reaction: Succinate to FumarateEnzyme: Succinate dehydrogenase

Reaction Type: Oxidation

Description: The two hydrogens of succinate leave to an acceptor,

FAD. Then this reaction yields fumarate and FADH2.

Step 9.

Reaction: Fumarate to MalateEnzyme: Fumerase

Reaction Type: Not described.

Description: Not described.

Step 10.

Reaction: Malate to Oxaloacetate

Enzyme: Malate dehydrogenaseReaction Type: Oxidation

Description: Malate is dehydrogenated to form oxaloacetate. The

hydrogen acceptor is NAD. So this reaction yields

NADH.

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