Unit 2 KA5-KA7

Question 1

Metabolism and adverse conditions

Answer 1

The extreme heat and drought in summer and the extreme cold and lack of food in winter in some environments creates conditions that are beyond the tolerable limits for an organism’s normal metabolic activity.
If an organism is to survive these conditions, it has to either be adapted or able to avoid them.

Question 2

Dormancy

Answer 2

This is part of some organisms’ lifecycle. This is to allow survival during a period when the costs of continued metabolic activity would be too high.
During dormancy there is a decrease in metabolic rate, heart rate, breathing rate and body temperature. Metabolic rate can be reduced during dormancy to save energy.
Types of dormancy:- predictive
consequential

Question 3

Predictive dormancy

Answer 3

Predictive dormancy occurs before the onset of adverse conditions

Question 4

Consequential dormancy

Answer 4

Consequential dormancy occurs after the onset of adverse conditions
and is typical in unpredictable environments.

Question 5

Examples of dormancy

Answer 5

• hibernation

- aestivation

Question 6

Hibernation

Answer 6

Hibernation is a form of dormancy which enables some animals (usually mammals) to survive harsh winter conditions (low temperatures).

Question 7

Aestivation

Answer 7

Aestivation is a form of dormancy which enables some animals to
survive periods of high temperature or drought.

Question 8

Daily torpor

Answer 8

Daily torpor is a period of reduced activity in some animals with high
metabolic rates.
e.g. hummingbirds feed during the day and show torpor at night; bats feed at night and show torpor during the day.

Question 9

Migration

Answer 9

Migration is the regular, long-distance movement of animals from one place to another.
Migration avoids metabolic adversity by expending energy to relocate to a more suitable environment.
e.g. British swallows migrate to South Africa for winter.

Question 10

Influences on Migratory Behaviour

Answer 10

Migratory behaviour can be learned or innate.

Question 11

Innate behaviour

Answer 11

Innate behaviour is inherited. It is triggered by an external stimulus (e.g. change in day length)

Question 12

Learned behaviour

Answer 12

Learned behaviour develops as a result of experience – through watching other individuals or through trial and error.

Question 13

Techniques used to study long-distance migration

Answer 13

• Leg rings are metal bands containing an identification codes
• Satellite tracking gives precise information about the location of the animal.

Question 14

Environmental control of metabolism

Answer 14

Microorganisms include:-
1. bacteria
2. archaea (most extremophiles are archaea and live in extreme conditions that would be lethal to most other living things)
3. some species of eukaryotes (e.g. yeast)
Microorganisms use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways.

Question 15

Use of Microorganisms

Answer 15

Microorganisms are widely used in research and industry because:-

1. They are easy to cultivate
2. They reproduce & grow quickly 3. They are adaptable

Question 16

Variations in growth media and the control of environmental factors

Answer 16

Microorganisms are grown under controlled conditions in a lab. The growth medium can be either:-
 solid agar
 liquid nutrient broth
The growth medium will contain:-
1. an energy source - such as
Chemical substrates (carbohydrate) or light (if it can photosynthesise).
2. a supply of raw materials for the biosynthesis of complex
substances (e.g. amino acids for making proteins)
Many microorganisms can produce all the complex molecules required for biosynthesis, including the amino acids required for protein synthesis, vitamins and fatty acids.
Other microorganisms require that these are added to the growth media.

Question 17

Culture Conditions

Answer 17

Culture conditions include:-
S sterility
T temperature (control of)
O oxygen levels 
P pH
Sterile conditions in fermenters reduce competition with desired micro- organisms for nutrients and reduce the risk of spoilage of the product.

Question 18

Phases of Growth

Answer 18

Growth is the irreversible increase in dry biomass of an organism. Growth of bacteria and yeast (unicellular organisms) is measured by an
increase in cell number over a set period of time. There are 4 phases of growth:-
1. Lag phase
2. Log/exponential phase 3. Stationary phase
4. Death phase

Question 19

Lag phase

Answer 19

 There is no cell division, so no increase in cell number.

 In this phase enzymes are induced to metabolise substrate.

Question 20

log/exponential phase

Answer 20

 This contains the most rapid growth of micro-organisms due to plentiful nutrient shortages

Question 21

stationary phase

Answer 21

 This occurs due to the nutrients in the culture media becoming depleted and the production of toxic metabolities.
 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 outcompete other micro-organisms.

Question 22

death phase

Answer 22

 This occurs due to lack of nutrients in the culture and the toxic accumulation

Question 23

Measuring Growth

Answer 23

A viable cell count (counts only living micro-organisms) whereas total cell counts involve counting viable and dead cells.
Only viable cell counts show a death phase where cell numbers are decreasing.

Question 24

Genetic control of metabolism

Answer 24

Wild strains of microorganisms can be selected to be used in industrial processes.
These wild strains, however, may have to be improved (possibly by changing their DNA) before they can be used in industry.
Strains of microorganisms can be improved by:-
 Mutagenesis
 Recombinant DNA technology

Question 25

Mutagenesis

Answer 25

Mutagenesis is the process by which mutations are induced.
This is achieved through the use of mutagenic agents (e.g. UV light and other forms of radiation) or mutagenic chemicals.

If the mutant strain produced is improved in some way (e.g. increased production of a required product/ability to grow on a low-cost medium), it can then be cultured for use.

Question 26

Recombinant DNA Technology

Answer 26

Humans can use advances in DNA technology to manipulate DNA within the laboratory and improve microorganisms.
Recombinant DNA technology involves transferring gene sequences from one organism to another and even from one species to another.
A vector is a DNA molecule used to carry foreign genetic information into another cell and both plasmids and artificial chromosomes are used as vectors during recombinant DNA technology.
Artificial chromosomes are preferable to plasmids as vectors when larger fragments of foreign DNA are required to be inserted

Question 27

Restriction Endonuclease

Answer 27

Is an enzyme which cuts open plasmids and specific genes out of
chromosomes, leaving sticky ends.
Complementary sticky ends are produced when the same
restriction endonuclease is used to cut open the plasmid and the gene from the chromosome.

Question 28

DNA ligase

Answer 28

Is an enzyme which seals the donor DNA fragment (gene) into the plasmid by joining the complementary sticky ends together. Thus a recombinant plasmid containing recombinant DNA is formed

Question 29

Vectors

Answer 29

To be an effective vector plasmids and artificial chromosomes contain restriction sites, regulatory sequences, an origin of replication and selectable markers.