Infectious agents and STIs

Question 1

Types of microbes?

Answer 1

VIRUS: small with DNA/RNA with a protein capsid. No cytoplasm, mitochondria, nucleus

BACTERIA: small, prokaryotic, with 1 DNA, cytoplasm, membrane + rigid cell wall. No nucleus, mitochondria. (Gram positive = blue/purple stain, Gram negative = red stain)

FUNGI: Larger than virus, eukaryotic, DNA, uni/multicellular, cytoplasm, membrane, mitochondria, nucleus

PARASITE: Largest, unicellular, DNA, nucleus, cytoplasm, mitochondria, membrane, flagella,

Question 2

HIV:
Structure?

Replication cycle?

Diagnosis?

Answer 2

• Has an envelope with proteins in it.
  2 copies of RNA
  Enzymes e.g. reverse transcriptase, integrase, protease etc.

1. HIV binds to TCR on host cell using gp120 protein
2. gp41 changes shape to help virus fuse with membrane. Virus enter cell and loses its envelope
3. Viral RNA is reverse transcribed into DNA, which goes into host nucleus = viral proteins made to form a capsid
4. Capsid buds off cell to form new HIV molecule
   - Symptoms too general, so lab tests are carried out. HIV testing and PCR.

Question 3

Herpes Simplex Virus (HSV):
Structure?

Replication cycle?

Diagnosis?

Answer 3

• HSV Type 1 and 2 both have an enveloped structure with a nucleocapsid inside
• Viral shedding: goes into cell, replicate, leave cell
• Clinical and lab-based

Question 4

Human Papilloma Virus (HPV):
Diagnosis?

Hep B:
Diagnosis?

Answer 4

• Clinical and lab-based

- Lab-based: Look for viral antigens and DNA