Unit 2 KA6

Question 1

Prokaryote

Answer 1

Organism lacking a true nucleus, eg. bacteria, archaea

Question 2

Eukaryote

Answer 2

Cells containing a true nucleus, eg. plant, animal and fungal cells

Question 3

Properties of micro-organisms

Answer 3

Highly adaptable and can grow on a variety of substrates, including waste materials.

Make a wide range of metabolic products which are useful to humans. eg. alcohol, antibiotics.

Easy to cultivate - they grow and reproduce rapidly.

Question 4

Growth medium

Answer 4

A substance used for culturing micro-organisms.

Can be solid agar or liquid broth.

Various substances can be added to control the metabolism of the micro-organisms being grown.

Question 5

Composition of growth media

Answer 5

Carbohydrates (eg. starch) - energy source and to build all organic molecules.

Water - (hydrogen/oxygen) for building molecules. Oxygen is required for respiration. (Final H acceptor)

Nitrates and phosphates - for building amino acids, DNA and ATP.

Sulfates - for building some amino acids

Beef extract - contains vitamins and fatty acids which cannot be synthesised by some micro-organisms.

Enzyme inhibitors and inducers to divert metabolic pathways.

Question 6

Biosynthesis

Answer 6

The production of complex molecules within cells.

Question 7

Aseptic technique

Answer 7

Sterile conditions used when preparing and inoculating growth media with micro-organisms.

Includes using disinfectant, heating equipment in a flame and protective clothing.

Prevents contamination with rival microbes which may compete with the desired microbe and cause spoilage of the product.

Question 8

Fermenter

Answer 8

Used to grow microbes in optimum conditions on a large scale to produce antibiotics, enzymes etc.

Question 9

Sensors/probes

Answer 9

Used to monitor conditions inside a fermenter, so that optimum conditions can be maintained.

Information is fed back to a computer which can alter factors such as the flow rate of cooling water, to adjust the temperature inside the fermenter. (Negative feedback control)

Question 10

Paddle/stirrer

Answer 10

Blades inside a fermenter that are driven by a motor.

Stirs the culture to prevent the cells from sinking or settling.

Question 11

Growth

Answer 11

The rate of production of new cells is faster than the rate of cell breakdown, resulting in an increase in biomass (living tissue).

Question 12

Measuring microbial growth

Answer 12

Dry and weigh a sample of culture to measure biomass.

Or count cell numbers in a known volume using a haemocytometer.

Question 13

Mean generation time (doubling time)

Answer 13

The time taken for a population of micro-organisms to double in number.

Question 14

Semi-logarithmic graph paper

Answer 14

Has a normal linear scale along the x-axis and a logarithmic scale along the y-axis.

This allows a large range of values to be plotted.

Microbial populations increase rapidly and are difficult to plot on a normal graph.

Question 15

Phases of growth

Answer 15

The pattern shown by microbial populations in culture, when number of viable cells is plotted on semi-log graph paper against time.

Shows population growth in 4 phases - lag, log, stationary, death

Question 16

Lag phase

Answer 16

The cells adjust to the growth medium, and their metabolic rate increases.

They induce enzymes to prepare for growth.

Question 17

Log phase

Answer 17

A period of exponential growth at the maximum rate possible.

The number of cells doubles with each division, so the population increases rapidly and the graph goes steeply upwards.

Nutrients are plentiful and there are no other limiting factors.

Question 18

Stationary phase

Answer 18

Rate of new cell production = rate of cell death, and the graph levels out.

Nutrients begin to run out, toxic waste products and secondary metabolites start to build up, and the rate of cell division decreases.

Question 19

Death phase

Answer 19

More cells are dying than are being produced, due to lack of nutrients and accumulation of toxic products.

The number of viable cells drops.

Question 20

Viable cell count

Answer 20

Only living cells are counted.

Allows a death phase to be seen.

Question 21

Total cell count

Answer 21

All cells, viable and dead, are counted.

The death phase cannot be seen in a total cell count.

Question 22

Haemocytometer

Answer 22

A specialised microscope slide used to count the number of cells in a sample of known volume.

Question 23

Primary metabolism

Answer 23

Occurs during periods of active growth (lag and log phases)

Substrates are broken down to release energy and produce molecules such as amino acids (biosynthesis) which are essential for growth.

Question 24

Secondary metabolism

Answer 24

Produces substances that are not used for growth, but which may give an ecological advantage. eg. antibiotics

Happens during stationary phase, when the culture is under pressure and nutrients are running out.

Used to kill rival microbes which may compete for limited resources.

Many secondary metabolites are very useful to humans eg. penicillin (antibiotic)