Disease and Pathogens

Question 1

What is disease?

Answer 1

It is the change of normal structure and function of any part of the body.

Question 2

How is disease caused?

Answer 2

1) Non-infectious eg. poor diet/lifestyle
2) Infectious: pathogens
3) Can be transmitted from one organism to another

Question 3

What is a pathogen?

Answer 3

An organism or infectious particle which causes disease. It is also known as an antigen.

Question 4

List the stages of the infective process

Answer 4

1) Pathogens enter
2) Colonise host
3) Evade host defences
4) Multiply and circulate
5) Cause damage to an organism
6) exit host and repeat process

Question 5

Name the 7 different types of pathogens

Answer 5

1) Viroids
2) Prions
3) Viruses
4) Bacteria
5) Protists
6) Fungi
7) Parasites/ macroscopic pathogens

Question 6

Describe the role of viroids

Answer 6

1) They are the smallest known particle
2) Short pieces of RNA - no protein coat
3) Only have been identified as pathogens in plants

Question 7

Describe the role of Prions

Answer 7

1) Infectious, abnormally folded proteins
2) Usually cause degenerative neurological disease such as Mad Cow disease
3) Often spread by contaminated meat
4) If they come into contact with healthy proteins they can change the structure of that protein to a Prion
5) Prions are infections even at high temperatures and cannot be broken down by protease

Question 8

Describe the role of viruses

Answer 8

1) They invade the host cell and replicate inside the cell
2) After they finish replicating they burst the cell in order to spread to other cells
3) They DO NOT metabolise
4) They are composed of genetic material: (DNA, RNA)
5) Surrounded in a protein capsid
6) Can be controlled by a vaccine

Question 9

Describe the role of Bacteria

Answer 9

1) Unicellular prokaryotes
2) They contain a single chromosome, occasionally plasmids and flagella
3) Possess a peptidoglycan cell wall
4) Divide asexually by binary fusion
5) Produce harmful toxins which can make us ill

Question 10

What effect does bacteria have on tissue?

Answer 10

1) Destroy tissue through the enzymes they produce
2) Endotoxins: released into the surroundings as the bacteria grows
3) Exotoxins: Released when the infected cell lyses or breaks open

Question 11

How do you treat a bacterial infection?

Answer 11

1) Antibiotics - which can stop the reproduction of bacteria
2) Treatments of symptoms
3) Antiseptics - a chemical which destroys bacteria
4) Disinfectants
5) Antibodies

Question 12

What is a protist and describe its function

Answer 12

1) Single celled eukaryotic pathogen
2) Contain a metabolic system and consist of a cell bound by a cell membrane
3) Mostly free
4) Reproduce by mitosis
5) Transmission can occur via insect vectors

Question 13

What is Fungi and describe its function

Answer 13

1) Hetrotrophic multicellular eukaryotic organism
2) Majority are NOT pathogenic
3) Many fungal disease effect animal tissue eg. tinea

Question 14

What is a parasite?

Answer 14

A parasite is any organism living in or on another organism from which it obtains nutrition

Question 15

Describe what a parasite does

Answer 15

1) Does not kill the host
2) They are Multi cellular eukaryotes with a complex life cycle
3) Have a piercing and sucking mouthparts
4) Worms and hydatids eg. Tapeworms
5) Hooks and suckers eg. Hermaphrodites
6) They can also mimic host molecules

Question 16

Name some factors affecting infection

Answer 16

1) Pathogenicity - If the pathogen has an affect on the host
2) Tissue affinity - The pathogen must of been able to grow on infected tissue
3) Dosage - the amount needed to cause infection
4) Sensitivity of the host
5) Survival outside of the host
6) The defences of the host