ENVIRONMENTAL CONTROL OF METABOLISM

Question 1

microorganisms

Answer 1

micro-organisms are capable of using a wide range of substrates for metabolism and are used to produce a range of products from their metabolic pathways, that are beneficial to mankind
-archaea, bacteria and some species of eukaryotes

Question 2

use of microorganisms

Answer 2

They are used because of their adaptability, ease of cultivation and speed of growth.
EXAMPLE: YEAST = in the production of alcohol and bread-making.

Question 3

growth media

Answer 3

when culturing microorganisms, a growth media will provide the micro-organism with raw materials for biosynthesis as well as an energy source.

Question 4

raw materials

Answer 4

Many micro-organisms produce all the complex molecules required for biosynthesis, for example amino acids, vitamins and fatty acids. Other microorganisms require these to be supplied in growth media.

Question 5

culturing

Answer 5

When culturing micro-organisms, their growth media require raw materials for biosynthesis as well as an energy source.

Question 6

energy source

Answer 6

An energy source is derived either from chemical substrates or from light in photosynthetic micro-organisms.

Question 7

culture conditions

Answer 7

Sterile conditions in fermenters = reduce competition with desired microorganisms for nutrients / reduce risk of spoilage of the product
- sterility
-control of temperature
-oxygen levels
-pH

Question 8

phases of growth of microorganisms: lag phase

Answer 8

where enzymes are induced (to bring about) to metabolise substrates / where bacteria are metabolically active but not dividing / microorganisms adjust to conditions of culture

Question 9

phases of growth of microorganisms: log/exponential phase

Answer 9

contains the most rapid growth of microorganisms as a result of plentiful nutrients / bacteria are doubling at a constant rate

Question 10

phases of growth of microorganisms: stationary phase

Answer 10

occurs as a result of nutrients in the culture media become depleted + production of toxic metabolites [ BACTERIAL CELL DIVISION = BACTERIAL CELL DEATH]

Question 11

secondary metabolites

Answer 11

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 out compete other micro-organisms.

Question 12

phases of growth of microorganisms: death phase

Answer 12

occurs due to toxic accumulation of metabolites or the lack of nutrients in the culture / bacterial death exceeds cell division

Question 13

semi-logarithmic scales:

Answer 13

Semi-logarithmic scales are used in producing and interpreting growth curves.

Question 13

difference between viable/total cell counts

Answer 13

• Viable cell counts involve counting only the living microorganisms.
• Total cells counts involve counting viable and dead cells
• ONLY viable cell counts show a death phase where cell numbers are decreasing.