# DBT JRF 2020 — Question 55

Exam: DBT JRF 2020 · Section: B · Topic: Biochemistry · Difficulty: Hard

## Question

Which type of post-translational modification does not occur in plastids?

## Options

- **A.** glycosylation
- **B.** phosphorylation
- **C.** acetylation
- **D.** s-nitrosylation

## Answer

Option A

## Explanation

Pathogenesis sequence follows a logical cascade from initial host-pathogen contact to established disease: (1) Exposure — host encounters the pathogen (inhalation, ingestion, contact with contaminated surface/person). (2) Adhesion — pathogen attaches to host surface (epithelial cells, mucus) via specific adhesins binding to host receptors (e.g. pili binding to urinary epithelium; influenza HA binding to sialic acid). (3) Invasion — pathogen breaches physical barriers and enters tissues; some use toxins or enzymes (hyaluronidase, collagenase) to facilitate penetration; intracellular pathogens enter host cells. (4) Infection — pathogen multiplies, evades host immunity, produces toxins/effectors, and causes pathological damage. Order: Exposure → Adhesion → Invasion → Infection.

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