1. Unit 2 2.6 Environmental Control of Metabolism
Higher Biology
Unit 2
2.6 Environmental Control of Metabolism

2. Microorganisms
Microbes are tiny living things that can only be seen with a microscope.
Most microbes do not affect humans.
However, a small number can be harmful and there are many that are useful.
It is these useful microbes that are so important in industry.

3. Microorganisms Microbes are found in all three domains of life;
Prokaryotes
Bacteria
Archaea
Eukaryotes
Microbes are found in all three domains of life;
Eukaryotes
Bacteria
Archaea

4. Microorganisms
Using microbes in industry to make useful products, is often called biotechnology.
Microbes are used in industry because;
they reproduce rapidly
Their metabolism can be easily controlled

5. Stage 1 – Lag Phase Little (or no) increase in the number of cells.
Microbes adjust to the growth medium.

6. Stage 2 – Log Phase Cells grow and multiply at a maximum rate.
Microbes have ideal conditions for growth.

7. Stage 3 – Stationary Phase
No net increase in the number of cells.
The rate of production of new cells is equal to the death rate of old cells.

8. Stage 4 – Death Phase
The death rate of old cells is greater than the rate of production of new cells.
Concentration of respiratory substrate decreases and concentration of toxins (waste products) increases.

9. Log Graphs
Log graphs are used to show the growth of microbes during the log stage.
On log graphs, intervals on the y-axis increase from 1-10, then from and so on.

10. Log Graph Question How many cells survive after 6 minutes? 1300 4000
5000
5500

11. Primary Metabolism Occurs during the lag and log phases
Microbes break down substrates to release energy
Primary metabolites are produced by microbes
These are used for growth e.g. amino acids

12. Secondary Metabolism
Occurs at the end of the log phase and during the stationary phase
Secondary metabolites are produced by microbes
These are not used for growth

13. Secondary Metabolites
Can be toxic to some microbes.
Can confer an ecological advantage to the microbe e.g. antibiotics produced by fungi inhibit growth of bacteria, thus reducing competition.
Many have properties that are useful to humans e.g. ethanol.
Microbes used in industry are often required to over produce this metabolite.

14. Controlling Metabolism
The metabolic pathways of microbes can be regulated by controlling the action of enzymes. This is done through;
Enzyme induction
Enzyme inhibition

15. Controlling Metabolism
In this pathway metabolite C is the desired product.
Metabolite A is a precursor. It will be acted upon by the first enzyme in the pathway to produce metabolite B.

16. Controlling Metabolism
Metabolite B is an inducer.
A constant supply of metabolite B ensures that enzyme 2 remains active, converting B into C.

17. Controlling Metabolism
An inhibitor must be used to prevent enzyme 3 converting metabolite C into metabolite D.
This ensures mass production of the desired product – metabolite C.