Biochemistry Lecture 16: Glycolysis

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Questions and Answers

What is the net number of ATP generated from glucose to lactate?

2 (correct)

Which enzyme cleaves one molecule of glucose into two C3 molecules?

Lactate dehydrogenase

Phosphofructokinase

Fructose bisphosphate aldolase (correct)

Hexokinase

During which process is NADH recycled back to NAD?

Citric acid cycle

Electron transport chain

Lactate fermentation (correct)

Alcohol fermentation

How many molecules of NADH are produced up to pyruvate in glycolysis?

2 Signup and view all the answers

What happens to NADH if oxygen is present?

It is later oxidized in the electron transport chain. Signup and view all the answers

What is the role of PEP in glycolysis?

To phosphorylate glucose. Signup and view all the answers

In which tissues does the reduction of pyruvate to lactate primarily occur?

Muscle and some cancer cells Signup and view all the answers

During which stage of glycolysis is one ATP used?

The phosphorylation of glucose Signup and view all the answers

Which glycolytic intermediate has the highest concentration in a red blood cell?

Glucose Signup and view all the answers

What is the primary function of 2,3-bisphosphoglycerate in red blood cells?

Promotes the release of oxygen from deoxy-haemoglobin Signup and view all the answers

Which of the following glycolytic intermediates has the lowest concentration in a red blood cell?

1,3-Bisphosphoglycerate Signup and view all the answers

Which compound directly follows Fructose-1,6-bisphosphate in the glycolytic pathway?

Dihydroxyacetone phosphate Signup and view all the answers

What role does ATP play in the glycolysis process?

It provides energy for the phosphorylation of glucose. Signup and view all the answers

Which pathway is primarily utilized by E.coli and mammalian cells to break down glucose?

Emden Meyerhof Parnas (EMP) pathway Signup and view all the answers

What role does phosphoenol pyruvate (PEP) play in E.coli regarding glucose transport?

It is used as the phosphoryl donor in the phosphotransferase system. Signup and view all the answers

How does glucose enter eukaryotic cells?

Through phosphorylation by Hexokinase when ATP is used. Signup and view all the answers

At which stages of the glycolytic pathway is ATP consumed in mammalian cells?

During early stages before splitting glucose into C3 molecules. Signup and view all the answers

What is a key function of glucose phosphorylation in E.coli?

It prevents glucose from leaving the cell. Signup and view all the answers

Which enzyme is responsible for cleaving glucose into two C3 molecules in the EMP pathway?

Fructose bisphosphate aldolase Signup and view all the answers

Which pathway is mainly utilized by some bacteria, but not by E.coli or mammalian cells, for glucose metabolism?

Entner Doudoroff pathway Signup and view all the answers

What is the end product of glycolysis from one molecule of glucose?

Two C3 molecules Signup and view all the answers

Study Notes

Glycolysis Overview

Glycolysis is a pathway used to degrade glucose, varying among organisms with different enzymatic steps.
E. coli and mammalian cells primarily utilize the Embden-Meyerhof-Parnas (EMP) pathway.
Alternative pathways include Entner-Doudoroff and Phosphoketolase pathways, with E. coli employing the ED pathway for gluconate metabolism.

Glucose Transport into Cells

Prokaryotes (E. coli):
- Glucose is phosphorylated during transport via the phosphotransferase system (PTS).
- PEP (phosphoenol pyruvate) donates a high-energy phosphate, preventing glucose from exiting the cell.
Eukaryotes (Mammalian cells):
- Glucose is transported into cells and then phosphorylated by hexokinase using ATP to form glucose-6-phosphate.

EMP Glycolytic Pathway in Mammalian Cells

Initial stages consume ATP, while later stages produce ATP.
One glucose molecule (C6) is split into two C3 molecules by Fructose bisphosphate aldolase.
The bottom half of the pathway generates a total of four ATP.
Net ATP yield from glucose to lactate is 2.
Produces 2 NADH, typically reduced in the electron transport chain to generate more ATP when oxygen is present.
The reduction of pyruvate to lactate recycles NADH back to NAD, occurring primarily in muscle during exercise and some cancer cells.

EMP Glycolytic Pathway in E. coli

Similar to mammalian cells, one ATP is used early in the pathway, and one PEP is utilized, with ATP being produced later.
Results in a generation of three ATP from the bottom half of the pathway.
Total net ATP yield is 2, similar to mammalian cells, with 2 NADH produced.

Glycolytic Intermediate Structures

Key intermediates include:
- Glucose
- Glucose-6-phosphate
- Fructose-6-phosphate
- Fructose-1,6-bisphosphate
- Glyceraldehyde-3-phosphate
- 1,3-bisphosphoglycerate
- 2,3-bisphosphoglycerate
- 3-phosphoglycerate
- 2-phosphoglycerate
- Phosphoenolpyruvate
- Pyruvate

Energetics of Glycolysis in Red Blood Cells

Concentration of key glycolytic intermediates (in mM):
- Glucose: 5.0
- Glucose-6-phosphate: 0.083
- Fructose-1,6-bisphosphate: 0.031
- Glyceraldehyde-3-phosphate: 0.019
- 1,3-bisphosphoglycerate: 0.001
- ATP: 1.85
- ADP: 0.14
- Pi: 1.0
2,3-bisphosphoglycerate is predominantly found in red blood cells, aiding in oxygen release from deoxyhemoglobin.

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Description

This quiz explores the glycolytic pathway involved in glucose degradation in E.coli and mammalian cells. It covers the various enzymes and steps utilized in this significant biochemical process. Join to test your knowledge on glycolysis and its different enzymatic pathways!