Chapters 1-8

Question 1

Differences between Eukaryotes and Prokaryotes

Answer 1

Prokaryotes
1.   No Nucleus
2.  Single circular chromosome
3.  Extrachromosomal DNA is carried in plasmids 
 4. TX and TL can occur simultaneously 
Eukaryotes

1. DNA is carried on several chromosomes within nucleus
2. Nucleus bounded by nuclear membrane
3. TX requires mRNA formation and its movement out of nucleus into the cytoplasm
4. TL takes place on ribosomes
5. Cytoplasm is rich in membrane bound organelles which are absent in prokaryotes

Question 2

Difference between Gram Positive and Negative Bacteria

Answer 2

Gram Positive
- cell wall made of peptidoglycan, forms the external
surface of the cell

Gram Negative
– an additional outer layer rich in lipopolysaccharide

Question 3

Functions of the cell wall of Gram + and - Bacteria

Answer 3

Protection of the cell against the immune system and chemotherapeutic agents
Stimulating certain pathological responses
Confer antigenicity

Question 4

What are the Microparasites?

Answer 4

Viruses
Bacteria
Protozoa
Fungi

Question 5

What are the Macroparasites?

Answer 5

Worms

Anthropods

Question 6

Describe Microparasites

Answer 6

Replicate within the host and can multiply to produce a very large number of progeny, causing an overwhelming infection

Question 7

Describe Macroparasites

Answer 7

One infectious stage matures into one reproducing stage. The resulting progeny leave the host to continue the cycle, The level of infection is determined by the numbers of organisms that enter the body.

Question 8

The progeny of some Macroparasites does what?

Answer 8

Remain in the host and infections can lead to the build up of overwhelming numbers, particularly in immune suppressed patients

Question 9

Biological significance of host- pathogen relationship based on size

Answer 9

Organisms that are small enough to live inside cell establish a biological relationship with the host that is quite different from that of extracellular organisms- one that influences both disease and control.

Question 10

What is the basis of all host-pathogen relationships?

Answer 10

The exploitation by one organism of the environment provided by another.

Question 11

A pathogen’s primary requirement based on the nature and degree of exploitation is?

Answer 11

Supply of metabolic materials from the host in the form of nutrients or nuclear synthetic machinery

Question 12

Different species have adopted what kind of habits?

Answer 12

Intra or Extracellular

Question 13

Intracellular microparasites take their metabolic requirements from where?

Answer 13

The pool of nutrients available in the cell

Question 14

Extracellular microparasites take their metabolic requirements from where?

Answer 14

Present in tissue fluids or feeding directly on the host cells

Question 15

Macroparasites are found where and take their metabolic requirements from where ?

Answer 15

Extracellular

Ingesting and Digesting host cells or from tissue fluids or intestinal contents

Question 16

What is the problem that intracellular pathogens pose to the host?

Answer 16

Pathogens that live within the cells are largely protected against many of the host’s defense mechanisms, especially anti-bodies

Question 17

Control of infections due to intracellular pathogens relies on what?

Answer 17

Depends on intracellular killing mechanisms
Short Range mediators
Cytotoxic Agents
may destroy the pathogen and the host cell, leading to tissue damage

Question 18

Targeting the activity of pathogens that live within cells is a problem why?

Answer 18

Difficult to achieve selective action against the pathogen while leaving the cell intact

Question 19

Pathogens can live in what important cells?

Answer 19

The cells responsible for host’s immune and inflammatory mechanisms therefore depress the host’s defensive abilities.

Question 20

The advantages of intracellular life for pathogens

Answer 20

Provides access to host’s nutrient supply and its genetic machinery and allows escape from host surveillance and antimicrobial defenses.

Question 21

Can an organism by wholly intracellular?

Answer 21

No, if it is to replicate successfully, transmission must occur between the host’s cells, and this inevitably involves some exposure to the extracellular environment.

Question 22

What is the advantage of the extracellular phase during the development of the pathogen?

Answer 22

It provides an opportunity to control infection through defense mechanisms such as phagocytosis, antibody and complement.

Question 23

Transmission between cells can involve what?

Answer 23

The destruction of the initially infected cell and contribute to tissue damage and general host pathology

Question 24

The most important constraint on development and survival is?

Answer 24

Exposure to the components of the host’s defense mechanisms.