2.6 Environmental Control of Metabolism

Question 1

What are the three domains of life?

Answer 1

Prokaryotes, Eukaryotes, Archaea

Question 2

Why are microorganisms useful in research and industrial processes?

Answer 2

• cheap
• grow fast
• easy to cultivate
• ability to produce many different products

Question 3

What do microorganisms need to survive?

Answer 3

Energy source and raw materials for biosynthesis

Question 4

What four factors must be monitored when culturing cells?

Answer 4

• Sterility
• Temperature
• Oxygen Concentration
• pH

Question 5

Define ‘Sterile’

Answer 5

Free from contamination

Question 6

Why is making the culture sterile important?

Answer 6

Contaminating Micro-organisms may compete for resources and limit the growth of culture and so this must be resolved

Question 7

Why is a temperature an important factor to be controlled?

Answer 7

Important to ensure enzymes are working at their optimum in order to achieve the maximum growth rate

Question 8

How is temperature monitored in a culture?

Answer 8

Using a thermometer

Question 9

Define ‘growth’

Answer 9

Growth is the irreversible increase in dry biomass of an organism

Question 10

What is ‘Generation Time’?

Answer 10

Number of time taken for one cell to divide into two daughter cells

Question 11

What is the difference between the total cell count and the viable cell count?

Answer 11

Total cell count - number of cells visible in field of view (dead or alive)
Viable cell count - number of cells that are alive

Question 12

What is used to count the total cell count and the viable cell count?

Answer 12

Haemocytometer

Question 13

What are the four stages in the growth of a microorganism?

Answer 13

1 - Lag
2 - Log/Exponential
3 - Stationary
4 - Death

Question 14

Describe the Lag phase

Answer 14

Microbes are adjusting to condition

Question 15

Describe the Log/Exponential phase

Answer 15

contains the most rapid growth of micro-organisms due to plentiful nutrients.

Question 16

Describe the Stationary Phase

Answer 16

• Occurs due to the nutrients in the culture media becoming depleted and the production of toxic metabolites.
• Results in rate of new cell production = rate of cell death.
• Secondary metabolites are also produced.

Question 17

Describe the Death Phase

Answer 17

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

Question 18

Give an example of a secondary metabolite that can confer an ecological advantage

Answer 18

Antibiotics