Glycolysis is the first stage of carbohydrate metabolism in which one molecule of glucose is converted into two molecules of pyruvate through a series of enzyme-catalyzed reactions.It is the most fundamental pathway for energy production and occurs in almost all living cells.
The term “Glycolysis” is derived from two Greek words:
- Glyco = Sugar
- Lysis = Breakdown
Therefore,glycolysis literally means “breakdown of glucose.”
Definition
Glycolysis is the metabolic pathway in which one molecule of glucose (6-carbon compound) is converted into two molecules of pyruvate (3-carbon compounds) with the production of ATP and NADH.
Site of Glycolysis
- Occurs in the cytoplasm (cytosol) of both prokaryotic and eukaryotic cells.
- Does not require mitochondria.
- Can occur in both aerobic and anaerobic conditions.
Importance of Glycolysis
- It is the first step of glucose metabolism.
- Produces ATP,which serves as the immediate energy source for cells.
- Generates NADH for oxidative phosphorylation under aerobic conditions.
- Provides pyruvate for the Krebs (TCA) cycle.
- Supplies intermediates for the synthesis of amino acids,nucleotides,and lipids.
- It is the only source of ATP in mature red blood cells because they lack mitochondria.
- Provides energy during anaerobic conditions such as vigorous exercise.
Overall Chemical Reaction of Glycolysis
The overall reaction of glycolysis is:
Glucose + 2 NAD+ + 2 ADP + 2 Pi →
2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O
Flow Diagram of Glycolysis
The complete glycolytic pathway is shown below.This diagram illustrates every intermediate compound,enzyme involved,ATP consumption,ATP generation,and NADH formation.
Phases of Glycolysis
The glycolytic pathway is divided into two major phases.
1. Energy Investment Phase (Preparatory Phase)
- Occurs from glucose to glyceraldehyde-3-phosphate.
- Consumes 2 ATP molecules.
- Prepares glucose for energy extraction.
2. Energy Payoff Phase
- Occurs from glyceraldehyde-3-phosphate to pyruvate.
- Produces 4 ATP molecules.
- Produces 2 NADH molecules.
- Results in a net gain of ATP.
Summary of Glycolysis
| Parameter | Value |
|---|---|
| Location | Cytoplasm (Cytosol) |
| Starting Molecule | Glucose |
| Final Product | 2 Pyruvate |
| ATP Consumed | 2 ATP |
| ATP Produced | 4 ATP |
| Net ATP Gain | 2 ATP |
| NADH Produced | 2 NADH |
| Oxygen Requirement | Not Required |
| Total Number of Reactions | 10 Enzyme-catalyzed Steps |
Discover more from Pharmacy Helper
Subscribe to get the latest posts sent to your email.