L2 - An Introduction to microbes

Question 1

Name the four types of micro-organisms that cause disease

Answer 1

• viruses
• bacteria
• fungi
• parasites

Question 2

Name two of the three common features of a virus

Answer 2

Presence of a nucleic acid
Protein coat
Spikes for cell adhesion

Question 3

Name two ways in which
A) DNA viruses are classified
B) RNA viruses are classified

Answer 3

Type of nucleic acid - e.g. ss or ds RNA or DNA. May use reverse transcriptase or not

Presence of envelope - envelopes or non-enveloped. Envelope is a lipid membrane

In RNA viruses they can also be classified by shape e.g. helical/isocahedral

Question 4

What is the name of the classification system used to classify viruses?

Answer 4

The Baltimore classification

Question 5

What are bacteriophages?

Answer 5

Viruses which infect bacteria

Question 6

Why can bacteriophages be particularly dangerous in resistance?

Answer 6

Bacteriophages can transfer genes for virulence factors and resistance between bacteria

Question 7

Describe 3 common features of bacterium

Describe some other features a bacterium may have

Answer 7

1) plasma membrane
2) cell wall
3) pili for adhesion
4) ribosomes
5) circular DNA with no discernible nuclear membrane

1) flagella for motility
2) plasmids

Question 8

What is the function of the glycocalyx?

Answer 8

Cell adhesion to surfaces

Protection from antibodies and phagocytosis

Question 9

Describe the structural differences between gram positive and gram negative cell walls in bacteria

Answer 9

Gram positive - thick, multi-layered peptidoglycan cell wall. More peptidoglycan

Gram negative - thin cell wall composed of two membranes with peptidoglycan in between. Less peptidoglycan

Question 10

What does gram staining detect and how does this distinguish between gram positive and gram negative bacteria?

Answer 10

Gram staining detects peptidoglycan. During the stain alcohol is added which dissolves the small amount of peptidoglycan in the gram negative bacteria thus differentiating them

Question 11

What colour do
a) gram positive bacteria
b) gram negative bacteria
stain?

Answer 11

a) purple

b) red (after counter staining)

Question 12

Name the major bacterial shapes

Answer 12

Coccus (spherical)
Bacillus (rods)
Spirillus

Question 13

Give the two arrangements of cocci bacteria

Answer 13

Clusters or chains

Question 14

Bacteria can also be classified by their oxygen tolerance. Define the following

1) aerobes
2) anaerobes
3) obligate anaerobes
4) obligate aerobes

Answer 14

1) can survive in the presence of oxygen
2) can survive in the absence of oxygen
3) require lack of oxygen for survival
4) require oxygen for survival

Question 15

Name two differences between eukaryotes and prokaryotes

Answer 15

Eukaryotes have nuclear envelopes
Eukaryotes contain membrane bound organelles
Different ribosomal subunits - bacteria 70s eukaryotes 80s
Prokaryotes have a cell wall
Prokaryotes have circula DNA

Question 16

Name the two classes of fungi and how they are classified

Answer 16

Yeast - single felled

Moulds - multicellular

Question 17

Name the two types of parasite and how they are different

Answer 17

Protozoa - single felled

Helminths (worms) - multi-cellular