Infectious diseases

Question 1

Define ‘pathogenic’

Answer 1

Pathogenic is causing a disease

Question 2

2. With regards to microbial relationships, complete the following table:

Answer 2

Question 3

List TWO differences between ‘gram-negative’ and ‘gram-positive’ bacteria

Answer 3

1. Gram-Positive thick Gram-Negative: thinner cell wall
2. Gram-Positive stain purple, GN stains pink

Question 4

Describe TWO key differences between ‘exotoxins’ and ‘endotoxins’

Answer 4

1. Exotoxins: gram-positive & negative bacteria/ Endotoxins: only gram-negative
2. Exo: Released by a living microbe/ Endo: released after organism death
3. Exo: very toxic: diphtheria, E-coli/ Endo: less toxic: salmonella

Question 5

With regards to resident and transient microflora, list:

1. TWO body locations where microflora is present
2. TWO body locations where microflora is absent

Answer 5

1. Present: Nasal cavity, skin, mouth, small and large intestine, vagina and perineum.
2. Absent: Blood, cerebrospinal fluid (csf), lungs, stomach, uterus, fallopian tubes, ovaries, bladder and kidneys.

Question 6

1. Describe FOUR ways in which viruses can escape the immune system

Answer 6

1. They hide inside the host cells (can be latent).
2. They do not have a metabolism of their own — hence anti-microbial agents cannot be targeted towards enzymes.
3. They do not have many structures of their own.
4. Able to mutate — this allows them to change their surface antigens and avoid host immune response.

Question 7

Explain the following terms Fungi

Answer 7

Fungi are eukaryotic organisms.
• Fungi can be single-celled or very complex multicellular organisms.
• Fungi have a cell wall that contains melanin.
• Fungi are found everywhere; e.g. soil, mouldy bread, medicine, food.

Question 8

List FOUR factors that promote growth of fungi in the body

Answer 8

1. Warmth
2. Moisture
3. Rich nutrition (keratin, glucose)
4. Acidity

Question 9

Name ONE example of a protozoa

Answer 9

single cells and have no cell wall, just a cell membrane: Malaria parasites

Question 10

Define the following terms:

1. Epidemic
2. Pandemic
3. Endemic

Answer 10

1. Epidemic: Large outbreak of a disease (large groups)
2. Pandemic: Worldwide
3. Endemic: Restricted to an area

Question 11

Describe the structure of a virus.

Answer 11

They are not cells but a strand of RNA or DNA in a hard protein coat: capsid.

Question 12

Name ONE example of Helminths and life cycle

Answer 12

Parasitic worms: intestinal parasites. Egg, larva, adult