Metabolism and Survival, KA 5-7

Question 1

Adverse conditions

Answer 1

Many environments vary beyond the tolerable limits for normal metabolic activity for any particular organism.

Question 2

How do animals react to adverse conditions?

Answer 2

Some animals have adapted to survive adverse conditions by dormancy while others avoid them by migration.

Question 3

What is dormancy?

Answer 3

Dormancy is part of some organisms’ life cycle to allow survival during a period when the costs of continued normal metabolic activity would be too high.
The metabolic rate can be reduced during dormancy to save energy.
During dormancy there is a decrease in metabolic rate, heart rate, breathing rate and body temperature.

Question 4

When does predictive dormancy occur?

Answer 4

Predictive dormancy occurs before the onset of adverse conditions.

Question 5

When does consequential dormancy occur?

Answer 5

Consequential dormancy occurs after the onset of adverse conditions.

Question 6

Examples of dormancy

Answer 6

Some mammals survive during winter/low temperatures by hibernating.
Aestivation allows survival in periods of high temperature or drought.
Daily torpor is a period of reduced activity in some animals with high metabolic rates.

Question 7

What is migration?

Answer 7

Migration avoids metabolic adversity by expending energy to relocate to a more suitable environment.
Migratory behaviour can be innate and learned.

Question 8

How is long-distance migration studied?

Answer 8

Specialised techniques are used to study long-distance migration.
Examples of specialist techniques are satellite tracking and leg rings.

Question 9

Growth curves of micro-organisms

Answer 9

Semi-logarithmic scales are used in producing or interpreting growth curves of micro-organisms.

Question 10

Viable and total cell count

Answer 10

Viable cell counts involve counting only the 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 11

Micro-organisms

Answer 11

Micro-organisms are archaea, bacteria and some species of eukaryotes.
Micro-organisms use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways.

Question 12

Why are micro-organisms used in research and industry?

Answer 12

Micro-organisms are used because of their adaptability, ease of cultivation and speed of growth.

Question 13

Complex molecules for biosynthesis

Answer 13

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

Question 14

Raw materials for biosynthesis

Answer 14

When culturing micro-organisms, their growth media require raw materials for biosynthesis as well as an energy source.
An energy source is derived either from chemical substrates such as glucose or from light in photosynthetic micro-organisms.

Question 15

Culture conditions

Answer 15

The fermenter and its contents must be kept sterile and there should be control of temperature, pH and oxygen levels.
Sterile conditions in fermenters reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product.

Question 16

What happens in the lag phase?

Answer 16

The lag phase is where enzymes are induced to metabolise substrates.

Question 17

What happens in the log/exponential phase?

Answer 17

The log/exponential phase contains the most rapid growth of micro-organisms due to plentiful nutrients.

Question 18

Why does the stationary phase occur and what happens in it?

Answer 18

The stationary phase occurs due to the nutrients in the culture media becoming depleted and the production of toxic metabolites.
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 19

Why does the death phase occur?

Answer 19

The death phase occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture.

Question 20

How can wild strains of micro-organisms be improved?

Answer 20

Wild strains of micro-organisms can be improved by mutagenesis, or recombinant DNA technology.

Question 21

What is mutagenesis and how does it work?

Answer 21

Mutagenesis is the creation of mutations.
Exposure to UV light and other forms of radiation or mutagenic chemicals results in mutations, some of which may produce an improved strain of micro-organism.

Question 22

What is a vector?

Answer 22

A vector is a DNA molecule used to carry foreign genetic information into another cell.

Question 23

Give two types of vector

Answer 23

Recombinant DNA technology involves the use of recombinant plasmids and artificial chromosomes as vectors.

Question 24

When are artificial chromosomes used?

Answer 24

Artificial chromosomes are preferable to plasmids as vectors when larger fragments of foreign DNA are required to be inserted.

Question 25

What is the role of restriction endonucleases in recombinant DNA technology?

Answer 25

Restriction endonucleases cut 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 26

What is the role of ligase in recombinant DNA technology?

Answer 26

Ligase seals the gene into the plasmid.

Question 27

What do recombinant plasmids and artificial chromosomes contain?

Answer 27

Recombinant plasmids and artificial chromosomes contain:

1. Restriction sites
2. Regulatory sequences
3. An origin of replication
4. Selectable markers.

Question 28

Restriction sites

Answer 28

Restriction sites contain target sequences of DNA where specific restriction endonucleases cut.

Question 29

Regulatory sequences

Answer 29

Regulatory sequences control gene expression.

Question 30

Origins of replication

Answer 30

An origin of replication allows self-replication of the plasmid/artificial chromosome.

Question 31

Selectable markers

Answer 31

Selectable markers such as antibiotic resistance genes protect the microorganism from a selective agent (antibiotic) that would normally kill it or prevent it growing.
Selectable marker genes present in the vector ensure that only micro-organisms that have taken up the vector grow in the presence of the selective agent (antibiotic).

Question 32

Safety concerns in recombinant DNA technology

Answer 32

As a safety mechanism, genes are often introduced that prevent the survival of the micro-organism in an external environment.

Question 33

Use of recombinant yeast cells

Answer 33

Recombinant yeast cells can be used to produce active forms of the protein which are inactive in bacteria.
Recombinant yeast cells may be used, as plant or animal recombinant DNA expressed in bacteria may result in polypeptides being incorrectly folded.