Exam

Question 1

What is cell growth?

Answer 1

Growth is a result of both cell division and a change in cell growth

Question 2

Cell growth phases

Answer 2

1. Lag phase
2. Exponential phase
3. Deceleration phase
4. Stationary phase
5. Death phase

Question 3

When does the lag phase take place?

Answer 3

Directly after innoculation

Question 4

What happens during the lag phase?

Answer 4

• Microorganisms reorganize their molecular constituents
• Enzymes are synthesized or repressed
• Inoculum adapt to the new environment

Question 5

What happens during the exponential phase?

Answer 5

• Cells have adjusted to new environment
• Cell number density and cell mass increase exponentially with time
• Balanced growth occurs
• Cell metabolism is set up to achieve maximum rates of reproduction

Question 6

What happens during the deceleration growth phase?

Answer 6

• Growth starts to decelerate due to the depletion of essential nutrients and the accumulation of toxic by-products
• The rapidly changing environment results in unbalanced growth
• Cell is restructured to increase the prospects of cellular survival in a hostile environment

Question 7

What happens during the stationary phase?

Answer 7

• Net growth rate is equal to zero
• Growth rate = death rate
• Cells are still metabolically active and produce secondary metabolites
• Total cell mass concentration stays constant, but number of viable cells decrease
• Cell lysis occurs (cryptic growth)
• No growth, but secondary metabolite production (antibiotics, hormones).

Question 8

What happens during the death phase?

Answer 8

• Difficult to differentiate between stationary phase and death
• Depletion of nutrients or toxic product accumulation

Question 9

Three major categories of microbial growth

Answer 9

Growth associated product formation
Non-growth associated product formation (specific production rate is constant)
Mixed growth associated product formation

Question 10

What happens during growth associated product formation?

Answer 10

Products form simultaneously with the microorganisms

Question 11

When does non-growth related product formation take place?

Answer 11

During the stationary phase when growth rate = 0

Question 12

When does mixed growth associated product formation take place?

Answer 12

During the slow growth phase and the stationary phase