2.6 Environmental Control of Metabolism

Question 1

State the three domains of life

Answer 1

1. Archaea
2. Bacteria
3. Eukaryota

Question 2

Explain why microorganisms are often used in research and industry

Answer 2

• They are easy to culture (grow)
• They reproduce and grow quickly
• Adaptable
• Use a wide variety of substrates for metabolism
• Produce a range of products from their metabolic pathways

Question 3

Explain why microorganisms being adapatable makes them useful for both research and industry

Answer 3

It means we can control their metabolism easily

Question 4

Describe the specific environmental conditions needed for microorgansism to grow

Answer 4

• Any complex molecules the microorganism cannot synthesise.
• For example: amino acids, vitamins and fatty acids.
• An energy source from chemical substrates or light
• Sterility
• Temperature
• Oxygen levels
• pH

Question 5

Why is sterility important when growing microorganisms?

Answer 5

Prevents contamination reducing potential competition and the chance of spoilage of the product

Question 6

Define ‘doubling time’

Answer 6

The time taken for a cell to divide

Question 7

Define ‘total cell count’

Answer 7

counting alive and dead cells

Question 8

Define ‘viable cell count’

Answer 8

counting alive cells only

Question 9

List the four phases of microorganism growth

Answer 9

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

Question 10

Describe what happens during the lag phase of microorganism growth

Answer 10

enzymes are induced to metabolise substrates.

Question 11

Describe what happens during the log phase of microorganism growth

Answer 11

rapid growth of micro-organisms due to plentiful nutrients.

Question 12

Describe what happens during the stationary phase of microorganism growth

Answer 12

nutrients in the culture media becoming depleted and the production of toxic metabolites. Secondary metabolites are also produced.

Question 13

Describe what happens during the death phase of microorganism growth

Answer 13

toxic accumulation of metabolites or the lack of nutrients in the culture.

Question 14

Explain what a secondary metabolite is

Answer 14

A substance that confers an ecological advantage by allowing the micro-organisms which produce them to outcompete other micro-organisms

Question 15

Give an example of a secondary metabolite

Answer 15

Antibiotics