1. CHAPTER 2 Major Metabolic Pathway

2. Major Metabolic Pathway
Introduction to metabolism and bioenergetics.
Glucose metabolism: Glycolysis and TCA cycle,
Respiration.
Metabolism of nitrogenous compounds and hydrocarbons.
Overview of biosynthesis for small and macromolecules, anaerobic and autotrophic metabolism.

3. Major challenges in bioprocess development:
To select an organism that can efficiently make a given product
Before 1980 only naturally occurring organisms were available (wild type organism).
With the advent of genetic engineering, it is possible to remove or add genes to an organism to alter its metabolic functions in a predetermined manner (metabolic engineering)
It is important to understand the metabolic pathways in natural organisms either to use them directly or to metabolically engineer them to make a desired, novel product.

4. OR

5. Metabolic Pathways
Metabolism: a complete set of chemical reactions that occur in living cells, allowing cells to grow and reproduce, maintain their structures, and respond to their environments.

6. Characteristics of metabolism: 1. Varies from organisms to organism
2. Effected by environmental condition.
Even the same species may produce different product when grown under different nutritional and environmental regulation.
Example: Saccharomyces cerevisiae (baker’s yeast)
This indicates metabolic regulation not only by oxygen , but also by glucose. This effect is known as the Crabtree effect.
Therefore, control of metabolism is important in bioprocess.
Condition
Product
anaerobic
ethanol
aerobic
Yeast cells
aerobic (high glucose conc.)

7. ~ produce energy to the cell
~ requires energy
Glucose glycogen

8. -Living cell require energy for biosynthesis, transport of nutrient, motility and maintainance. -Energy is obtained from the catabolism of carbon compounds (carbohydrate) -Carbohydrates are synthesized from CO2 and H2O in the present of light by photosynthesis.

9. It is the part of biochemistry concerned with the energy involved in making and breaking of chemical bonds in the molecules found in biological organisms.

10. Bioenergetics Sunlight Photosynthesis by autotrophs :
CO2 + H2O → carbohydrates
Autotrophs
or heterotrophs
Catabolism
generating energy,
e.g ATP
Anabolism
requiring energy

11. Autotrophs and Heterotrophs
Organisms are divided into autotrophs and heterotrophs according to their energy pathways.
Autotrophs are those organisms that are able to make energy-containing organic molecules from inorganic raw material by using basic energy sources such as sunlight. Plants are the prime example of autotrophs, using photosynthesis.
All other organisms must make use of food that comes from other organisms in the form of fats, carbohydrates and proteins. These organisms which feed on others are called heterotrophs.

12. Three major categories of metabolic reactions:
(I) degradation of nutrients (II) Biosynthesis of small molecules (III) Biosynthesis of large molecules

13. Energy is mainly stored or transferred by adenosine triphosphate (ATP) ~ (contains high-energy phosphate bonds)
Other energy carrying compounds include GTP, UTP and CTP.

16. Embden-Meyerhof-Parnas (EMP)
Glucose Catabolism
Glucose
Glycolysis or
Embden-Meyerhof-Parnas (EMP)
Anaerobic metabolism
Aerobic metabolism
Fermentation: ethanol,
acetic acid, lactate.
Tricarboxylic acid (TCA)
or (Krebs)
or (Citric acid cycle)
(pyruvate is converted to CO2 +NADH)
Oxidative phosphorylation

19. Glucose (6C) is broken down into 2 PGAL's (3C)
This requires two ATP's

20. 2 PGAL's (3C) are converted to 2 pyruvates
This creates 4 ATP's and 2 NADH's
The net ATP production of Glycolysis is 2 ATP's

25. Respiration
Respiration reaction sequence is also known as electron transport chain
oxidative phosphorylation- forms ATP
Electron carried by NADH + H+ and FADH2 are transferred to oxygen via a series og electron carriers, forming ATP
NADH + H+ results in 3 ATP
FADH2 results in 2 ATP

28. Why 36 ATP? Glycolysis: 2 ATP Krebs Cycle: 2 ATP
Electron Transport Phosphorylation: 32 ATP
Each NADH produced in Glycolysis is worth 2 ATP (2 x 2 = 4) - the NADH is worth 3 ATP, but it costs an ATP to transport the NADH into the mitochondria, so there is a net gain of 2 ATP for each NADH produced in gylcolysis
Each NADH produced in the conversion of pyruvate to acetyl COA and Krebs Cycle is worth 3 ATP (8 x 3 = 24)
Each FADH2 is worth 2 ATP (2 x 2 = 4)
= 32
Net Energy Production: 36 ATP

31. Control sites in aerobic glucose metabolism
Several enzyme in glycolysis and Krebs cycle are regulated by feedback inhibition.
In glycolysis,
fructose-6-phosphate + ATP fructose-1,6-
diphosphate + ADP
At high ATP/ADP ratios,phosphofructokinase is inactivated
Effect of Oxygen concentration- Pasteur effect
Inhibition is important to alter cellular metabolism
phosphofructokinase
Relation of Pasteur effect with glycolysis, Krebs cycle and electron transport chain?

32. Reading Assignment Metabolism of nitrogenous compounds
Nitrogen fixation
Metabolism of hydrocarbons

33. Hydrocarbon Catabolism
Hydrocarbon: C & H
- Aliaphatic hydrocarbon
e.g. octane, C8H18
polyethylene –HC=CH-
- Aromatic hydrocarbon
naphthalene
Metabolism of hydrocarbon
- Requires oxygen
- Hydrocarbons are converted to acetyl-CoA which is metabolized by TCA cycle.
- Challenges : low solubility in aqueous solution.
available microorganisms are limited
Pseudomonas, Mycobacteria
naphthalene

34. Nitrogen Compounds Catabolism
Nitrogen compounds can be used for C, N and energy sources
Proteins → peptides → amino acids → converted to other amino acids or organic acids and ammonia by deamination.
- organic acids: acetyl-CoA into TCA cycle, lipids
- amino acids: proteins, other amino acids or enter TCA cycle
- ammonium: amino acid, protein, nucleic acids
Nucleic acids → ribose/deoxyribose, phosphoric acid and purine/pyrimidine
- sugar: glycolysis and TCA
- Phosphoric acid: ATP, lipids, nucleic acids
- bases: nucleic acids, urea, acetic acids

38. Anaerobic metabolism
Compare with aerobic pathway?
Electron acceptor

40. Autotrophic metabolism
Heterotropic growth – organic molecules serve ac C source
Autotrophs- obtain C from CO2
Calvin cycle or Calvin-Benson cycle :provide building blocks for autotrophic growth
Energy: light (photoautotrophs) or chemicals (chemoautotrophs)

41. Photosynthesis
Glycolysis and TCA

42. Phases in photosynthesis
Light phase
Dark phase
The overall reaction:
6CO2 + 6H2O + light → C6H12O6 + 6O2.

43. 2 1 5 3 4 6