Key Area 6

Question 1

What are micro-organisms

Answer 1

Archaea, bacteria and some species of eukaryotes

Question 2

Why are microorganisms used in biology

Answer 2

Because of their adaptability, ease of cultivation and speed of growth

Question 3

Describe the conditions required for growth of microorganisms

Answer 3

1. Sterile conditions
2. Control of temperature
3. Oxygen levels
4. pH

Question 4

What is a growth media

Answer 4

A growth medium is a solid or liquid substance used to grow, transport or store microorganisms
Liquid is called broth
Solid is made of agar jelly

Question 5

What are the four phases in a growth curve of microorganisms

Answer 5

1. Lag phase
2. Log/exponential phase
3. Stationary phase
4. The death phase

Question 6

Describe the lag phase

Answer 6

microorganisms adjust to the conditions of the culture by inducing the production of enzymes that metabolise the available substrates

Question 7

Describe the log/exponential phase

Answer 7

The rate of growth is at its highest due to lots of nutrients

Question 8

Describe the stationary phase

Answer 8

The culture medium becomes depleted and secondary metabolites are produced. Nutrients are being consumed at the same rate of bacterial growth

Question 9

Describe the death phase

Answer 9

Lack of nutrients and toxic accumulation of metabolites causes death of cells

Question 10

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

Answer 10

A viable cell count only counts the living microorganisms
Total cell count is both viable and dead cells

Question 11

What is primary metabolism

Answer 11

Metabolism during the lag and log phase: breakdown of substrate and production of primary metabolites

Question 12

What is secondary metabolism

Answer 12

Metabolism at the end of log phase and during the entire stationary phase: production of secondary metabolite that are not used for growth