Microbiology

Question 1

What are four arguments against viruses as living organisms?

Answer 1

• They do not grow by increasing in size
• They cannot carry out independent metabolism
• They do not respond to external stimuli
• They have no cellular structure

Question 2

What is an extracellular viral particle called?

Answer 2

A virion

Question 3

What are lysogenic viruses?

Answer 3

Viruses that can lay dormant for a long time before lysing their host cell

Question 4

What is a retrovirus? What are two applications of them?

Answer 4

A virus that uses RNA as its genetic material

It is called a retrovirus because they have reverse transcriptase, which transcribes their RNA into DNA. This DNA then incorporates itself into the host genome (HIV is an example).

• Used in genetics to deliver DNA to a cell (vector)
• Can be used in medicine for gene therapy

Question 5

What is the primary function of bacterial plasmids?

Answer 5

Conferring resistance to antibiotics

Question 6

What is the bacterial cell wall made out of? What is its primary function? What extra feature aids this function?

Answer 6

Peptidoglycans

Helps to prevent the hypertonic bacterium from bursting. Some bacteria have a slimy polysaccharide mucoid like capsule on the outer surface for protection.

Question 7

How is power for flagellum generated?

Answer 7

By a proton motive force

Question 8

List the shape classifications of bacteria (3) along with gram staining classification (2)

Answer 8

Cocci: spherical or elliptical

Bacilli: rod shaped/cylindrical

Spirilli: helical or spiral

If a Gram stain stains a bacteria, they are gram-positive (thicker peptidoglycan layer), if they do not retain the stain, they are gram-negative. Gram-negative bacteria are more resistant to antibiotic.

Question 9

If we start with 2 bacteria and follow for 3 generations, how many bacteria do we end up with?

Answer 9

b = B x 2^n

b = 2 x 2^3

b = 2 x 8

b = 16 bacteria after 3 generations

Question 10

What are the three forms of genetic recombination that bacteria participate in?

Answer 10

Transduction: phages act as a vector transferring DNA between bacteria

Transformation: Bacteria incorporate free DNA from immediate environment

Conjugation: Part of the DNA strand may be passed from one mating type to another through a hollow tube (pilus)

Question 11

What are saprophytic bacteria?

Answer 11

Heterotrophic bacteria that obtain their food from dead organic matter

Question 12

What are the two types of autotrophic bacteria?

Answer 12

Photosynthetic

Chemoautotrophic (obtain energy from oxidation)

Question 13

What are the two types of bacteria in respect to oxygen in the environment? What is it called when one can survive in another condition and one cannot?

Answer 13

Aerobic (metabolize in presence of oxygen)

Anaerobic (metabolize in absence of oxygen - ferment)

• facultative anaerobe can survive in oxygen
• obligate anaerobe would die in oxygen

Question 14

List three types of symbiosis

Answer 14

• Mutualism (both benefit)
• Parasitism (one benefits, other is harmed)
• Commensalism (one benefits, other isn’t effected)

Question 15

Are fungi prokaryotic or eukaryotic? Describe their food gathering and structure.

Answer 15

Eukaryotic.

Fungi absorb food through chritinous cell walls and

They can be unicellular (eg. yeast) or filamentous (eg. mushrooms).

Filamentous fungi have individual filaments called hyphae, which collectively form a mycelium.

Question 16

How do fungi reproduce?

Answer 16

Often asexually with spores (conidia) released from a sporangium or through asexual budding (as in yeast).
Sexual reproduction involves the fusion of opposite mating types to produce asci, basidia or zygotes (all diploids which must undergo meiosis to produce haploid spores).

Question 17

True or false. If resources are unlimited, fungi are expected to grow exponentially.

Answer 17

true

Question 18

In eukaryotes, oxidative phosphorylation occurs in the mitochondrion. The analagous structure used by bacteria to carry out oxidative phosphorylation is ___?

Answer 18

The plasma membrane

Question 19

Which of the following pieces of evidence most strongly supports the hypothesis of mitochondrial origin?

A. Mitochondria have fewer genes than typical bacterial cells have
B. Mitochondria contain hundreds of different enzymes
C. The diameters of mitochondria and typical present-day bacteria are approximately equal
D. Nitrogen fixing bacteria live symbiotically inside the cells of present day plants

Answer 19

D. Nitrogen fixing bacteria live symbiotically inside the cells of present day plants

This shows that such a relationship is possible between bacteria and multicellular organisms and best supports the hypothesis of mitochondrial origin.

Question 20

When an AIDS virus has been incorporated into a CD4 cell, but has not yet been replicated, the viral genetic information is located in the CD4 cell’s ___?

Answer 20

Nucleus

The viral coat fuses with the membrane, dumping its RNA core into the cell. ONce dumped, this RNA core would be transformed into DNA by reverse transcriptase and the viral DNA would then become incorporated

Question 21

Conjugation is a feature of gram-? bacteria. How does it confer an advantage to the bacteria?

Answer 21

Conjugation is a feature of gram-negative bacteria. It confers the advantages of sexual reproduction on the bacterium. The plasmid benefits by being able to move from one host bacterium to another through the conjugation pilus.

Question 22

Of the following processes, which allows viral DNA to insert into a host’s genome?

• Splicing
• Recombination
• Replication
• Transcription

Answer 22

Recombination

Of the 4 answer choices, only recombination will allow a foreign piece of DNA to be incorporated into the host genome. As a result, the viral DNA will be transcribed along with the host’s genes by the cell’s own machinery.

Question 23

What do helper T cells do?

Answer 23

They activate all types of lymphocytes in the body (T-lymphocytes, B-lymphocytes etc.)

Activation of B lymphocytes will lead to the production of specific antibodies which will recognize invading foreign organisms, whereas activation of cytotoxic T cells (T-lymphocytes) will cause the direct elimination of these microbes.