Environmental Control of Metabolism

Question 1

What do microorganisms include?

Answer 1

Archaea
Bacteria
Some species of eukaryotes

Question 2

Describe micro-organisms range of substrates and products

Answer 2

Micro-organisms use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways

Question 3

Why are micro-organisms used?

Answer 3

Adaptability
Ease of cultivation
Speed of growth

Question 4

When culturing micro-organisms, what does their growth media require?

Answer 4

Raw materials for biosynthesis as well as an energy source

Question 5

Many micro-organisms produce all the complex molecules required for biosynthesis, such as?

Answer 5

Amino acids
Fatty acids
Vitamins

Question 6

Other micro-organisms require?

Answer 6

These to be supplied to them

Question 7

Microorganisms need an energy source for growth, where is this derived from?

Answer 7

Either from chemical substrates or from light in photosynthetic microorganisms

Question 8

Explain the need for culture conditions

Answer 8

Sterility in fermenters- reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product
Control of temperature
Control of oxygen levels
Control of pH

Question 9

Describe the phases of growth of microorganisms

Answer 9

Lag phase
Log/exponential phase
Stationary phase
Death phase

Question 10

Describe the lag phase

Answer 10

The period where enzymes are induced to metabolise substrates

Question 11

Describe the log/exponential phase

Answer 11

Containing most rapid growth of micro-organisms due to plentiful nutrients

Question 12

Explain the stationary phase

Answer 12

Occurs due to the culture media becoming depleted and the production of toxic metabolites.
Secondary metabolites are also produced, such as antibiotics. In the wild these metabolites confer an ecological advantage by allowing the micro-organisms which produce them to outcompete other micro-organisms.

Question 13

Explain the death phase

Answer 13

Occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture

Question 14

Compare viable cell counts to total cell counts

Answer 14

Viable cell counts count living cells only, whereas total cell counts involves counting viable and dead cells

Question 15

What can a viable cell count show?

Answer 15

A death phase where cell numbers are decreasing

Question 16

What is generation time?

Answer 16

The time taken for a cell to divide into two (also called doubling time) during the exponential growth