2.6 - Environmental Control of Metabolism

Question 1

Microorganism

Answer 1

A microorganism is a unicellular organism that is too small to see without a microscope.

Microorganisms use a wide variety of substrates for metabolism. As a result, they produce a range of products from their metabolic pathways.

Question 2

Examples of Microorganisms

Answer 2

• Archae
• Bacteria
• Soem species of eukaryote

Question 3

Qualities of Microorganisms

Answer 3

Microorganisms are used becuase of their:
* Speed of growth
* Ease of cultivation
* Adaptability (can manipulate metabolism)

Question 4

Growth Media Definition

Answer 4

Growth media is a substance used to grow, transport, or store microorganisms.

Question 5

Growth Media

Answer 5

Microorganisms’ growth media requires raw materials for biosynthesis as well as an energy source. Many microorganisms produce all of the complex molecules required for biosynthesis e.g amino acids, vitamins and fatty acids.

Other microorganisms require complex molecules to be supplied in the growth media. An energy source is derived either from chemical substrates or from light in photosynthesis microorganisms.

Question 6

Culture Conditions

Answer 6

Temperature, pH, and oxygen levels all need to be controlled. This is done by growing microorganisms in a fermenter e.g pH is controlled through using buffers.

Microorganisms also need sterile conditions in a fermenter which reduces competition for nutrients as well as the risk of products being spoiled.

Question 7

Phases of Growth

Answer 7

1. Lag phase
2. Log phase
3. Stationary phase
4. Death phase

Question 8

Lag Phase

Answer 8

Lag phase is where enzymes are induced to metabolise substrates.

Question 9

Log Phase

Answer 9

Log phase contains the most rapid growth of microorganisms due to plentiful nutrients.

Question 10

Stationary Phase

Answer 10

Stationary phase occurs due to the nutrients in the culture media becoming depleted and the production of metabolites.

Secondary metabolites are also produced e.g antibiotics.

In the wild these metabolites are an ecological advantage by allowing the microorganisms which produce them to outcompete other microorganisms.

Question 11

Death Phase

Answer 11

Death phase occurs due to the build up of toxic metabolites or the lack of nutrients in the culture.

Question 12

Viable Cell Count

Answer 12

Viable cell count invole counting only the living organisms.

Only viable cell counts show a death phase where cell numbers are decreasing. Semi-logarithmic graphs are used to produce and interpret growth curves of microorganisms.

Question 13

Total Cell Count

Answer 13

Total cell count involv counting viable cells as well as dead cells.