3.3 Procaryotes Questions and Answers

3.3 Procaryotes – Questions and answers

Q1.

Bk Ch3 S3.3 Q1

Outline the main differences between procaryotic and eucaryotic cells.

A1.

Bk Ch3 S3.3 A1

Procaryotic cells lack membrane-bound organelles and are always independent unicellular organisms, whereas eucaryotic cells are characterised by having membrane-bound organelles and while some are unicellular they also include large multicellular organisms.

Q2.

Bk Ch3 S3.3 Q2

Explain how

athe electron microscope, and

badvances in molecular biology have increased our knowledge and understanding of procaryotic organisms.

A2.

Bk Ch3 S3.3 A21

aThe electron microscope has allowed scientists to explore the internal structures of procaryotic organisms and compare them with larger eucaryotic cells.

bAdvances in molecular biology have led scientists to understand that some of the functional differences between procaryotic organisms are based upon differences in the molecular structure of organelles.

Q3.

Bk Ch3 S3.3 Q3

What is a plasmid? What are the only kinds of organisms in which plasmids are found?

A3.

Bk Ch3 S3.3 A3

A plasmid is a small circular thread of DNA found in procaryotic organisms.

Q4.

Bk Ch3 S3.3 Q4

aName the two groups into which procaryotes are divided.

bDescribe the distinguishing features for each group.

A4.

Bk Ch3 S3.3 A4

aProcaryotes can be divided into the archaea and the eubacteria.

bThe cell membranes of archaea contain a series of branching lipids; they also have a large enzyme involved in RNA synthesis. Eubacteria do not have branched lipids in the cell membrane and only have a small enzyme involved in RNA synthesis. Eubacteria contain a chemical called murein in the cell wall; this is not present in the cell wall of archaea. Eubacteria are also sensitive to the antibiotics streptomycin and chloramphenicol whereas archaea are not.

Q5.

Bk Ch3 S3.3 Q5

For any one named type of procaryotic organism

a describe the main features of its environment

b identify the role of this organism in its ecosystem.

A5.

Bk Ch3 S3.3 A5

A general rather than detailed answer will suffice for all parts of this question. The answers will depend on the type of procaryote chosen.

Q6.

Bk Ch3 S3.3 Q6

Stromatolites that exist today are also represented by fossil remains that date back more than 3000 million years.

aWhat kind of organism is a stromatolite?

bExplain how stromatolites contributed to change in environmental conditions over millions of years.

A6.

Bk Ch3 S3.3 A6

aStromatolites are cyanobacteria belonging to the group called eubacteria.

bStromatolites have existed for more than 3000 million years. Because they have existed for so long and in great abundance they have had a significant impact on the balance of gases in the atmosphere. Their photosynthetic activity over millions of years has reduced the level of carbon dioxide in the atmosphere and increased the level of free oxygen.

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